A hybrid polymer brush containing poly(ethylene glycol) (PEG) chains and polyhedral oligosilsesquioxane (POSS) on a gold surface is presented that exhibits an excellent protein resistance and long-term stability. A series of hybrid polymer brushes with different length and numbers of PEG chains are fabricated through chemisorption of PEG-POSS-SH on the gold surface. Protein adsorption of these hybrid brushes is investigated. The amount of protein adsorption decreases with increasing lengths and numbers of PEG chains. After immersion in BSA solution for two months, the PPS4 brushes retain their protein resistance, while a PEG-SH layer loses its non-fouling performance. These POSS-containing hybrid polymer brushes might offer an alternative for modification of gold surface with an excellent protein resistance for long-term applications.

A hybrid polymer brush containing poly(ethylene glycol) (PEG) chains and polyhedral oligomeric silsesquioxane (POSS) units is immobilized on a gold surface and exhibits an excellent protein resistance with long-term stability.

Poly(D,L-lactide)-SS-poly(2-methacryloyloxyethyl phosphorylcholine) block copolymers conjugated with cholesterol are synthesized by ROP and ATRP using a novel kind of double-dead initiator. This facile strategy not only can endue block copolymers with disulfide bonds, but can also overcome the disadvantages inherent in the synthesis procedure for the copolymers. The resultant biomimetic copolymers can self-assemble into near-monodisperse micelles. Subsequently, they are used as a carrier to encapsulate a hydrophobic dye, and the release can be triggered by a redox reagent, dithiothreitol. MTT study shows that the as-prepared micelles has good biocompatibility to both normal and cancer cells. These properties indicate that these micelles may be used as promising drug delivery vehicles.

Near-monodisperse redox-sensitive micelles can be obtained from cholesterol-conjugated biomimetic copolymers, which are prepared by sequential ROP and ATRP using a novel kind of double-dead initiator. The resultant micelles can be used as a carrier to encapsulate hydrophobic guest molecules, and the release manner can be regulated by a redox reagent, DTT.

The synthesis and gene transfection efficiency of a series of novel amphiphilic triblock copolymers with two hydrophilic poly(2-(dimethylamino)ethyl methacrylate) (DMAEMA) blocks flanking a central hydrophobic poly[(R)-3-hydroxybutyrate] (PHB) block is reported. These copolymers have significantly lower toxicity compared to the polyethyleneimine (PEI) and PDMAEMA homopolymer. Unexpectedly, the incorporation of PHB significantly improves the gene transfection efficiency as compared to PEI or PDMAEMA homopolymers.

A series of novel triblock copolymers with poly(2-(dimethylamino)ethyl methacrylate) (DMAEMA) blocks flanking a hydrophobic poly[(R)-3-hydroxybutyrate] (PHB) block is synthesized and the gene transfection efficiencies of these polymers are reported. Compared with PEI or PDMAEMA homopolymers, the incorporation of PHB significantly improves the gene transfection efficiency. This exciting finding heralds new developments in the area of polymeric gene delivery vectors.

Targeted carrier systems (e.g., liposomes or nanoparticles) are used to specifically deliver drugs to a site of interest. Site-direction can be achieved by attachment of targeting molecules, such as peptides, DNA/RNA, or antibodies, to the surface of the carrier. Here, the formation of polymersomes with tumor-targeting potential is described. A single-domain antibody (A12) that specifically targets PlexinD1 (a transmembrane protein overexpressed in tumor vasculature) is equipped with an azide-functionality using expressed protein ligation. This azide-containing A12 can subsequently be attached to BCN-functionalized polymersomes using a strain-promoted azide alkyne cycloaddition, thereby forming polymersomes with tumor-targeting potential.

The preparation of polymersomes with tumor-targeting potential is described. To this end, polymersomes are equipped with a strained cyclooctyne and a tumor targeting single-domain antibody (A12) is functionalized with an azide using expressed protein ligation (EPL). Conjugation of the two yields polymersomes with an A12-coated surface.

Counter polyelectrolytes (PEs) having a degradable polyamide backbone and controlled thiolation are prepared. Their nanosized polyelectrolyte complexes (PECs) spontaneously crosslink under ambient conditions via bioreducible disulfide bonds. These PECs are regenerable after centrifugation, and resist degradation by proteases. They are stable to variations of pH and electrolyte concentration, similar to those encountered in biological milieu. However, they are unraveled in reductive conditions. These PECs act as efficient vectors for delivering entrapped cargo. They entrap with high efficiency, and controllably release, fluorescein isothiocyanate (FITC)-insulin (a model peptide) in vitro. Potent cellular internalization of FITC-insulin within human lung cancer cells with high cell viability is demonstrated.

Polyamide polyelectrolytes (PEs) with controlled thiolation are prepared from an L-aspartic acid-derived precursor, polysuccinimide. These counter PEs form complexes that undergo spontaneous, reagentless self-crosslinking via bioreducible disulfide bonds, significantly augmenting their stability under biorelevant conditions. These complexes efficiently transport an entrapped peptide cargo inside A549 cell lines with high cell viability.

A strategy of encapsulation of the antiTNF-α antibody on top of poly(lactide-co-glycolide) nanoparticles (PLGA NPs) is presented on the basis of the complexation of antiTNF-α with alginate (Alg) and subsequent assembly layer by layer with poly(L-lysine) (PLL). The assembly of the antiTNF-α/Alg complex with PLL and its stability in PBS and lysozymes are monitored on a planar support using a quartz crystal microbalance with dissipation. The assembly of the antiTNF-α/Alg complex on PLGA NPs is followed by zeta potential measurements. AntiTNF-α release from the PLGA NPs is measured in PBS at 37 and 60 °C and in the HepG2 cell line following NP uptake, using the Q-ADA kit detection kit. The release follows first-order kinetics with an initial burst. Intracellular release of antiTNF-α is confirmed by confocal Raman microscopy.

The antibody antiTNF-α and alginate are successfully encapsulated on top of PLGA nanoparticles. The antibody is first complexed with alginate and then assembled layer by layer on top of the nanoparticles. The release of antiTNF-α follows first-order kinetics. Intracelullar delivery is proven by confocal Raman microscopy.

Nanotechnology is finding ever increasing application in the life science arena where nanoparticles can be used to deliver cargoes in cells. However, a clear understanding of the relationship between the chemical properties of the particle and its uptake efficiency is lacking. Herein, the effects on particle cellular uptake following modification with a variety of spacers, all bearing a positive charge, but differing in length, and the influence on formation of the protein corona are investigated. Although no significant differences in the composition of the protein corona are detected, the spacer length influences the cellular uptake of the nanoparticles. These findings will allow the target-orientated functionalisation of particles to increase the specificity of cellular uptake.

The influence of varying the length of the spacer, attached to polymer nanoparticles, on the formation of a protein corona and cellular uptake are studied. Although the composition of the protein corona is not affected by different spacer lengths, an influence on cellular uptake can be identified.

A nanoscale biodegradable polymersome with pH-tuning on-off membrane is prepared via the self-assembly of poly(β-amino ester)-based amphiphilic copolymers. The pH-sensitive polymersome-like vesicle structure includes two layers that can encapsulate either hydrophobic or hydrophilic therapeutic drugs at physiological pH 7.4. Below a pH of 7.0, the polymersome membrane forms tunnels through which the drug cargo can be rapidly released. The size and morphology of the polymersome are measured by transmission electron microscopy (TEM) and dynamic light scattering (DLS). The pH sensitivity is confirmed by fluorescence spectroscopy. The pH-sensitive drug-delivery polymersome provides a simple and powerful smart carrier for the delivery and controlled release of drugs.

A nanoscale biodegradable polymersome with pH-tuning on-off membrane is prepared and utilized for the delivery and controlled release of drugs. The pH-sensitive polymersome includes two layers that can encapsulate either hydrophobic or hydrophilic therapeutic agents at physiological pH 7.4. Below pH 7.0, the polymersome membrane forms tunnels through which the drugs can be rapidly released.

This study describes the synthesis of a set of novel, degradable block copolymers for DNA transfection, and analyzes their physicochemical and biological properties. PEO macro-azoinitiators are used for the free radical copolymerization of DMAEMA and MDO, resulting in a series of different quaternized or non-quaternized block copolymers. All of the polymers show little cytotoxicity and full degradability, and thus, based on their favorable properties, may represent promising vectors for in vivo applications. Marked differences in DNA complexation efficacies and biological activities are observed, and one of the poly(PEG-co-(MDO-co-DMAEMA))s is identified as optimal for DNA transfection.

The synthesis of a set of novel, degradable, polymeric transfection vectors is described, based on copolymers of PEO, N,N-dimethylaminoethyl methacrylate and 2-methylene-1,3-dioxepane. All of the copolymers show only little cytotoxicity and efficient DNA complexation, and, in particular, the quaternized 57:43 poly(PEG-co-(MDO-co-DMAEMA)) copolymer is identified as optimal in cell transfection experiments.

Microwell chips (25 mm × 25 mm) are fabricated to select proper substrates for growing three-dimensional (3D) spheroids from mesenchymal stem cells (MSCs). Different bio-macromolecules and their combinations are immobilized on the chip by air plasma treatment and by polyelectrolyte interaction. Only a small number of MSCs (≈10⁵) are needed for each chip. The expression level of N-cadherin, a cell-adhesion molecule, is used as an indicator for cell-cell interactions. MSC spheroids expressing the highest N-cadherin level also show the greatest osteogenic potential. The microwell chip may be used as an efficient platform to screen bio-macromolecules that enhance the differentiation potential of MSCs.

Microwell chips (25 mm square) are manufactured and serve as a culture substrate-selecting platform for mesenchymal stem cells. Cells are grown in microwells coated with different biopolymers. Biopolymer substrates favoring cell differentiation can be selected based on the expression of N-cadherin, which is a cell-cell adhesion protein that may interact with the calcium on the polymer surface.

Acid-responsive electrospun fibers are fabricated by introducing sodium bicarbonate into PLLA fibers using an emulsion method. This novel electrospun fibrous scaffold exhibits a rapid acid-responsive controlled drug release (early stage) and stable three-dimensional (3D) structure as a tissue engineering scaffold (late stage) for cell growth.

Acid-responsive electrospun fibers are fabricated by introducing sodium bicarbonate into PLLA fibers using an emulsion-based method. These novel electrospun fibrous scaffolds exhibit a rapid acid-responsive controlled drug release (early stage) and stable 3D structure as tissue engineering scaffolds (late stage) for cell growth.

Biomimetic macroporous matrices are synthesized using natural polymers like gelatin and alginate in order to provide selective cell attachment to the matrix by controlled exposure of a functional polymer surface in a composite matrix using different crosslinking chemistry.

A detailed cellular entry mechanism of conjugated polymer nanoparticles (CPNs) is presented. Cancer cells pretreated with an inhibitor of caveolae-mediated endocytosis (CvME) exhibit decreased CPN uptake. High co-localization with caveolin-1 proteins found in the caveolae and caveosomes further confirms CvME of CPNs. Non-toxicity and non-destructive delivery pathways support that CPNs are promising carriers, minimizing content degradation during delivery.

Limited blood supply and the avascular nature of articular cartilage restricts its self repair capacity, frequently leading to osteoarthritis. This work focuses on scaffolds for tissue repair from natural polymers, for example gelatin, chitosan, and agarose in the form of composite. A novel way of fabrication, known as cryogelation, is presented, in which matrices are synthesized at sub-zero temperature. Cell seeded scaffolds incubated under appropriate conditions result in the accumulation of matrix components on the surface of the gel in the form of neo-cartilage. Neo-cartilage exhibits similarity to native cartilage with respect to its physical, mechanical and biochemical properties. Based on the similarities of neo-cartilage to the native cartilage, it can provide a new approach for the treatment of localised joint injuries.

Generation of scaffold-free neo-cartilage on cryogel matrices is observed in vitro on specially designed cryogel matrices. Neo-cartilage is characterized for its similarity to the native cartilage by biochemical, histological and mechanical analysis. The results exhibit similarity between neo and native cartilage, so it can be a potential material to treat the lesions generated during osteoarthritis.

A highly effective drug carrier is constructed by coating folic acid-terminated poly(ethylene glycol) (PEG-FA) on single walled carbon nanotubes (SWNTs) in a facile non-covalent method. The anti-cancer drug, doxorubicin (DOX), is further loaded on the surface of SWNTs at a very high loading efficiency, 149.3 ± 4.1%. The drug system (DOX/PEG-FA/SWNTs) exhibits excellent stability under neutral pH conditions such as serum, but dramatically releases DOX at reduced pH typical of the tumour environment and intracellular lysosomes and endosomes. With the help of FA, DOX/PEG-FA/SWNTs tend to selectively attach onto cancer cells and enter the lysosomes or endosomes by clathrin-mediated endocytosis. This can greatly improve the pharmaceutical efficiency and reduce potential side effects.

A folate-conjugated PEG coating on single walled carbon nanotubes is developed in a facile strategy that can target delivery of the anti-cancer drug, doxorubicin, into cancer cells and effectively induce cancer cell death, but shows negligible cytotoxicity to normal cells.

Combined cancer treatment via co-delivery of siRNAs and an anticancer drug can be a promising strategy due to the synergistic effect of simultaneously minimizing gene/drug administration. In this study, Bcl-xL siRNA and doxorubicin (DOX) are encapsulated into designed methoxy-poly(ethylene glycol)-block-poly(D,L-lactic acid) (mPEG-b-PLA) block copolymer polymersomes (PSomes). A study of the cytotoxicity of Bcl-xL siRNA and DOX co-encapsulated PSomes (CPSomes) shows more inhibited proliferation of MKN-45 and MKN-28 human gastric cancer cell lines than only gene- and drug-loaded ones. Consequently, these results demonstrate that co-delivery of genes and drugs using PSomes results in a synergistic efficacy and indicates the potential of PSomes as efficient nanocarriers for combined cancer therapy.

Successful delivery of small molecular drugs and therapeutic genes by Bcl-xL siRNA and doxorubicin (DOX) encapsulated polymersomes shows potential as a highly powerful nanocarrier-based dual therapy system for cancer treatment.

Amylose and polytetrahydrofuran (PTHF) are mixed in an aqueous solution to form inclusion complexes. DSC shows that immediate mixing results in complexes having lower melting temperatures compared with complexes prepared with longer mixing times. The washed complexes melt at higher temperatures compared with the corresponding unwashed complexes. XRD indicates that amylose–PTHF complexes diffract similar to amylose–fatty acids complexes (V_6I-amylose helices), with additional diffractions correlating with amylose–alcohol complexes (V_6II-amylose helices). This suggests that the structure of amylose–PTHF complexes is an intermediate or a mixture between V_6I- and V_6II-amylose. This shows that, besides residing inside the amylose helices, some PTHF chains are located in between the amylose helices.

Amylose and polytetrahydrofuran (PTHF) can form inclusion complexes that are able to self-assemble to form supramolecules. Amylose, with its hydrophobic cavity, acts as host molecule and PTHF acts as guest molecule. The resulting complexes induce the formation of the so-called V-amylose, which is influenced by the arrangements of the guest PTHF chains inside or in between the amylose helices.

Osteogenic/osteoinductive systems combine simvastatin, poloxamine Tetronic 908 (T908) and α-cyclodextrins (αCDs) in a supramolecular network that enhances the solubility/stability of the simvastatin hydroxy acid form and synergistically promotes osteoblast differentiation. Incorporation of 5% αCD transforms dilute T908 solutions (as low as 2% copolymer) into gels, enhances the osteoinductive activity of T908, and provides simvastatin sustained release for more than one week, which results in higher and more prolonged alkaline phosphatase (ALP) activity. The performance of the intrinsically osteoinductive polypseudorotaxane scaffold can be easily tuned by modifying the concentrations of T908, αCD, and simvastatin in a certain range of values. Moreover, the use of affordable, stable materials that can be sterilized applying a conventional method make the supramolecular gels advantageous candidates as scaffolds to be applied in the critical defect using minimally invasive techniques.

Osteogenic syringeable gels exploit the capability of osteoinductive poloxamine Tetronic 908 to form polypseudorotaxanes with αCD and to solubilize and sustainably release the simvastatin hydroxy acid form for synergic differentiation of mesenchymal stem cells to osteoblasts. αCD transforms dilute poloxamine/simvastatin dispersions into affordable osteogenic/osteoinductive networks that can be administered using minimally invasive techniques for local treatment of bone pathologies.

A combined sulfated silk fibroin scaffold is fabricated by modifying a knitted silk scaffold with sulfated silk fibroin sponges. In vitro hemocompatibility evaluation reveals that the combined sulfated silk fibroin scaffolds reduce platelet adhesion and activation, and prolong the activated partial thromboplastin time (APTT), thrombin time (TT), and prothrombin time (PT). The response of porcine endothelial cells (ECs) and smooth muscle cells (SMCs) on the scaffolds is studied to evaluate the cytocompatibility of the scaffolds. Vascular cells are seeded on the scaffolds and cultured for 2 weeks. The scaffolds demonstrate enhanced EC adhesion, proliferation, and maintenance of cellular functions. Moreover, the scaffolds inhibit SMC proliferation and induce expression of contractile SMC marker genes.

In order to develop small-diameter vascular grafts that have excellent hemocompatibility to prevent platelet adhesion and aggregation on the scaffold surface and simultaneously be suitable for vascular cell growth, a combined sulfated silk fibroin scaffold is fabricated by modifying a knitted silk scaffold with sulfated silk fibroin sponges. The scaffold may greatly improve the chances of successful vascular reconstruction.

An antioxidant microgel with both glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities is reported. Using computational design and genetic engineering methods, the main catalytic components of GPx are fabricated onto the surface of ferritin. The resulting seleno-ferritin (Se-Fn) monomers can self-assemble into nanocomposites that exhibit remarkable GPx activity due to the well organized multi-GPx catalytic centers. Subsequently, a porphyrin derivative is synthesized as an SOD mimic, and is employed to construct a synergistic dual enzyme system by crosslinking Se-Fn nanocomposites into a microgel. Significantly, this dual enzyme microgel is demonstrated to display better antioxidant ability than single GPx or SOD mimics in protecting cells from oxidative damage.

A dual enzyme microgel is constructed based on the covalent crosslinking of Mn-THPP-(PEG₂₀₀₀-BA)₄ and seleno-ferritin (Se-Fn). The microgel exhibits excellent antioxidative activity in the protection of mitochondria against oxidative stress and lipid peroxidation due to the synergism of the Mn^III porphyrin (SOD mimic) and Se-Fn (GPx mimic).

Amphiphilic triblock copolymers with carbonyl groups located either in the middle segment or in the third side block are synthesized by adjusting feeding sequence of the comonomers. The conjugation of hemoglobin (Hb) on the copolymer micelles is realized by condensation reactions of carbonyl with the amino groups of Hb, and the gas-binding capacity of Hb is well preserved. Interestingly, the reassembly behavior of Hb-conjugated micelles (HbM) is explored by adjusting the pH. As for triblock copolymers with a carbonyl-functionalized segment as the third block, Hb is rearranged into the inner core of micelles when the pH is adjusted close to the isoelectric point of Hb. Therefore, it may provide a new needed route for fabrication of protein carriers, which is different from the traditional encapsulation technique.

Hemoglobin-conjugated micelles are prepared by the amidation reaction between hemoglobin and polymeric micelles fabricated from triblock copolymer with two different monomer sequences. Hemoglobin can be partially entrapped into the core of the micelles when the pH is adjusted to the isoelectric point of the hemoglobin.

Human mesenchymal stem cells (MSCs) derived from various origins show varied differentiation capability. Recent work shows that cell shape manipulation via micropatterning can modulate the differentiation of bone-marrow-derived MSCs. Herein, the effect of micropatterning on the myogenesis of MSCs isolated from three different sources (bone marrow, fetal tissue, and adipose) is reported. All the well-aligned cells, regardless of source, predominantly commit to myogenic lineage, as shown by the significant upregulation of myogenic gene markers and positive myosin heavy chain staining. It is demonstrated that our novel micropattern can be used as a generic platform for inducing myogenesis of MSCs from different sources and may also have the potential to be extended to induce other lineage commitment.

The capability of a micropatterning platform in modulating cell shape to direct lineage commitment of human mesenchymal stem cells derived from different sources (i.e., bone marrow, fetal tissue, and adipose) is investigated. Myogenesis is shown to be the predominant differentiation activity at mRNA and protein levels in three types of micropatterned stem cells. The platform is thus demonstrated to be generic and could possibly be extended to any type of stem cell.

Platelets play a fundamental role in thrombus formation and in the pathogenesis of arterial thrombosis. Patterning surfaces for controlled platelet adhesion paves the way for adhesion and activation mechanisms in platelets and detection of platelet functional defects. Here, a new and simple method based on controlled polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) on the surface of styrene-block-(ethylene-co-butylene)-block-styrene (SEBS) is shown. The competition between polymerization and degradation enables platelet adhesion on SEBS to be switched on and off. The adhesive sites of the platelets can be down to single cell level, and the dysfunctional platelets can be quantitatively detected.

A patterned surface is fabricated based on controlled surface-initiated polymerization of monomer and degradation of the obtained polymer at the UV-exposed domains on the polymer surface with UV irradiation. Switching on and off of platelet adhesion on the polymer surface is realized with a precision down to single cell level. The dysfunctional platelets can be quantitatively detected based on the adhesive pattern.

Fluorescein isothiocyanate (FITC), a fluorescent probe, is coupled to amphiphilic monomethoxy poly(ethylene glycol)-block-poly(ε-caprolactone) (mPEG-PCL) copolymers. FITC-labeled mPEG-PCL copolymers self-assemble into micelles through the solvent evaporation method. The cellular internalization is examined using fluorescence microscopy on incubation of NIH-3T3 fibroblasts with micelles or free FITC solution. The effect of the hydrophilic/hydrophobic ratio on the endocytosis mechanisms is evaluated by fluorescence microscopy on culturing of human hepatoblastoma cells and human umbilical vein endothelial cells, individually, mixed with the micelles holding the same parameters including micelle size, shape, and surface charges.

Besides factors such as particle size, morphology, and surface charge, the hydrophilic/hydrophobic ratio of the micelle matrix also has a great effect on cellular uptake of micelles. The internalization of micelles with different hydrophilic/hydrophobic ratio into cells is through different endocytosis mechanisms.

Blood protein adsorption and blood platelet adhesion onto surface-attached poly(alkylacrylamide) networks that exhibit small and systematic variations in chemical composition are investigated. The polymer coatings are generated by depositing a thin layer of benzophenone-group-containing copolymer onto a solid substrate, followed by photo crosslinking and simultaneous surface-attachment. The correlation of the swelling of the obtained surface-attached networks with the adsorption of blood proteins and cellular adhesion is studied. The swollen surface-attached layers are inert to blood proteins and platelet cells. These results suggest that the hydrogel-coated materials are promising candidates for the generation of hemocompatible surfaces.

The interaction of surfaces with biological species is largely controlled through the initial adsorption of proteins. Surface-attached hydrogel coatings can suppress protein adsorption and, subsequently, cell or blood platelet adhesion. The strong swelling of theses coatings excludes proteins either via size exclusion and/or via entropic shielding.

The enzyme alkaline phosphatase (ALP) is added at different concentrations (i.e., 0, 2.5, and 10 mg · ml⁻¹) to oligo(poly(ethylene glycol)fumarate) (OPF) hydrogels. The scaffolds are either incubated in 10 mM calcium glycerophosphate (Ca–GP) solution for 2 weeks or implanted in a rat subcutaneous model for 4 weeks. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and alizarin red staining show a strong ability to form minerals exclusively in ALP-containing hydrogels in vitro. Additionally, the calcium content increases with increasing ALP concentration. Similarly, only ALP-containing hydrogels induce mineralization in vivo. Specifically, small (≈5–20 µm) mineral deposits are observed at the periphery of the hydrogels near the dermis/scaffold interface using Von Kossa and alizarin red staining.

Hydrogels are highly hydrated polymers with structural properties similar to soft tissues. In view of bone regenerative applications, the incorporation of alkaline phosphatase (ALP) within hydrogels is a simple and promising strategy to generate scaffolds with both an organic and inorganic phase. Specifically, the enzymatic hydrolysis of organic phosphates, diffused from the physiological environment, leads to the formation of minerals.

Mimicking hybrid extracellular matrix is one of the main challenges for bone tissue engineering (BTE). Biocompatible polycaprolactone/poly(α,β)-DL-aspartic acid/collagen nanofibrous scaffolds were fabricated by electrospinning and nanohydroxyapatite (n-HA) was deposited by calcium phosphate dipping method for BTE. Human mesenchymal stem cells (hMSCs) were cultured on these hybrid scaffolds to investigate the cell proliferation, osteogenic differentiation by alkaline phosphatase activity, mineralization, double immunofluorescent staining using CD90 and expression of osteocalcin. The present study indicated that the PCL/PAA/collagen/n-HA scaffolds promoted greater osteogenic differentiation of hMSCs, proving to be a potential hybrid scaffolds for BTE.

Biocompatible polycaprolactone/poly(α,β)-DL-aspartic acid/collagen nanofibrous scaffolds are fabricated by electrospinning and nanohydroxyapatite (n-HA) is deposited by a calcium phosphate dipping method. These scaffolds are characterized for fiber morphology, hydrophilicity, porosity, and tensile properties. Mesenchymal stem cell (MSCs) cultures on these nanofibrous scaffolds to facilitate cell adhesion, proliferation, mineralization, and osteogenic differentiation.

Several types of fibrous material containing poly(3-hydroxybutyrate) (PHB), nanosized TiO₂-anatase (nanoTiO₂), and chitosan oligomers are prepared by combining the electrospinning, electrospraying, and impregnation techniques. Simultaneous electrospinning/electrospraying provides uniform distribution of electrosprayed nanoTiO₂ along the PHB fibers and throughout the mat. Hybrid materials of different design manifest excellent photocatalytic activity, even after repeated use. They exhibit high bactericidal activity against Escherichia coli. In addition, the fibrous scaffolds are compatible with human mesenchymal stem cells and provide a favorable environment for their development.

Nanofibrous materials from poly(3-hydroxybutyrate), titanium dioxide nanoparticles, and COS are fabricated by an effective approach, consisting of electrospinning, electrospraying, and impregnation. The mats exhibit photocatalytic properties and a biocidal effect against pathogenic bacteria, and moreover, they provide a favorable environment for hMSCs.

DNA hybridization is a universal and specific mechanism for the recognition of biological targets. Some cationic polythiophene transducers sensitive to DNA structure have been previously utilized to detect such biomolecules. Further characterization of these systems indicates that both DNA sequence composition and length modulate the biosensor performance. It appears that different repeated sequence patterns cause different conformational changes of the polythiophene, from a more relaxed form to an extremely rigid one. A length difference between the DNA oligonucleotide probe and target has a detrimental effect on the fluorescent signal, but it can be attenuated by changing the sequence composition of the protruding target sequence. This demonstrates that the nature of DNA can be critical for hybridization-based detection systems.

The sequence composition is critical for DNA conformation and can impair its uses as a recognition mechanism in biosensing applications. Repeated sequence patterns such as polyT or PolyC, although similar, generate different sensor conformations when mixed with a polythiophene derivative DNA hybridization sensor. Knowledge of the impact of DNA sequences on biosensors can help improving biosensing systems.

The release of molecules entrapped within biogels is dictated by diffusion laws. Innovative biogel architectures are conceived and tested to control small molecule delivery from gelatin gels. The ionic interactions modulate the release of small molecules. Alginate is then added to gelatin gels and further hydrolyzed; the influence of viscosity is discussed. Next, various mixed gels are compared, such as a gelatin-alginate IPN and the original architecture of an alginate gel entrapped in a gelatin gel with or without a polysaccharidase. The relative influence of ionic interactions and diffusional constraints on the delivery of small charged molecules is explored, and a solution for controlling diffusion is proposed for any situation.

The use of various gelatin gels containing alginate as a molecular delivery system is described. The concept, development and use of several protein-polysaccharide architectures to retain very small molecules and control their release is described. The strategy presented here resides in the use of enzymes to hydrolyze one of the two phases of the gel in a highly controlled way.

Front Cover: Microcultures are arrayed on standard cell culture dishes by three dimensional poly(ethylene glycol)-dimethacrylate (PEG-DMA) microstructures. Lift-off produces freely growing cell patches, whose proliferation and migration can be observed over time. Growth rates are directly accessible by evaluation of the evolution of the microculture area. Further details can be found in the article by A.-K. Marel, S. Rappl, A. Piera Alberola, and J. O. Rädler* on page 595.

Alternative delivery entities are desirable in immunotherapies in which polyplexes are widely formed by electrostatic interactions to induce cellular uptake processes for bioactive molecules. In our study, biocompatible Ni(II)-nitrilo(triacetic acid)-modified poly(ethylene imine)-maltose (Ni-NTA-DG) is realized and evaluated as complexation agent against His-tagged peptides using fluorescence polarization and dynamic light scattering. The polyplexes are stable until a pH of 6.5–6.0, and also up to 50 mM of imidazole. A first uptake approach shows that polyplexes lead to an increase in peptide uptake in monocyte-derived immature dendritic cells. In summary, Ni-NTA-DG represents a promising (delivery) platform for forthcoming in vitro applications.

Ni-NTA-modified dendritic glycopolymers show high potential as a delivery system for coupling His-tagged antigens into dendritic cells (DC) under in vitro conditions. Ni-NTA-units prove to induce antigen uptake in DC. Stable polyplexes are demonstrated against slightly lower pH (pH ≥ 6.0) and different imidazole concentrations (10–50 µM) depending on the kind of polyplex.

An arginine-leucine block copolypeptide (R₆₀L₂₀) is synthesized, which is capable of forming vesicles with controllable sizes, able to transport hydrophilic cargo across the cell membrane, and exhibit relatively low cytotoxicity. The R₆₀L₂₀ vesicles also possess the ability to deliver DNA into mammalian cells for transfection. Although the transfection efficiency is lower than that of the commercially available transfection agent Lipofectamine 2000, the R₆₀L₂₀ vesicles are able to achieve transfection with significantly lower cytotoxicity and immunogenicity. This behavior is potentially due to its stronger interaction with DNA which subsequently provides better protection against anionic heparin.

Poly(L-arginine)₆₀-block-poly(L-leucine)₂₀ (R₆₀L₂₀) vesicles possess the ability to internalize cells and deliver DNA into mammalian cells for transfection. Although the transfection efficiency is lower than that of the commercially available transfection agent Lipofectamine 2000, R₆₀L₂₀ vesicles are able to achieve transfection with significantly lower cytotoxicity and immunogenicity.

Gelatin-methacrylamide (gelMA) hydrogels are shown to support chondrocyte viability and differentiation and give wide ranging mechanical properties depending on several cross-linking parameters. Polymer concentration, UV exposure time, and thermal gelation prior to UV exposure allow for control over hydrogel stiffness and swelling properties. GelMA solutions have a low viscosity at 37 °C, which is incompatible with most biofabrication approaches. However, incorporation of hyaluronic acid (HA) and/or co-deposition with thermoplastics allows gelMA to be used in biofabrication processes. These attributes may allow engineered constructs to match the natural functional variations in cartilage mechanical and geometrical properties.

Gelatin-methacrylamide (gelMA) hydrogel mechanical properties are predictably tuned by varying the crosslinking conditions. These gels also support chondrocyte survival and function. Furthermore, addition of hyaluronic acid and co-printing with thermoplastics allows for biofabrication with gelMA. These attributes may allow engineered constructs to match the natural functional variations in the mechanical and geometrical properties of cartilage.

Designing three-dimensional (3D) scaffolds for selective manipulation of cell growth is of high relevance for applications in regenerative medicine. Especially, scaffolds with oriented morphologies bear high potential to guide the restoration of specific tissues. The fabrication of hydrogel scaffolds that support long-term survival, proliferation, and unidirectional growth of embedded cells is presented here. Parallel channel structures are introduced into the bulk hydrogels by uniaxial freezing, providing stable, and uniform porosity suitable for cell invasion (pore diameters of 5–15 µm). In vitro assessment of the scaffolds with murine fibroblasts (NIH L929) shows a remarkable unidirectional movement along the channels, with the cells traveling several millimeters through the hydrogel.

Three-dimensionally (3D) structured bulk PEG-based hydrogels are fabricated by a uniaxial freezing process, resulting in centimeter-long parallel channel structures with a diameter of 5–15 µm. These scaffolds are investigated in cell culture with fibroblasts, revealing a striking unidirectional movement along the tubular, porous structures and demonstrating their great use for tissue regeneration.

Form-stable resorbable networks are prepared by gamma irradiating trimethylene carbonate (TMC)- and ε-caprolactone (CL)-based (co)polymer films. To evaluate their suitability for biomedical applications, their physical properties and erosion behavior are investigated. Homopolymer and copolymer networks that are amorphous at room temperature are flexible and rubbery with elastic moduli ranging from 1.8 ± 0.3 to 5.2 ± 0.4 MPa and permanent set values as low as 0.9% strain. The elastic moduli of the semicrystalline networks are higher and range from 61 ± 3 to 484 ± 34 MPa. The erosion behavior of (co)polymer networks is investigated in vitro using macrophage cultures, and in vivo by subcutaneous implantation in rats. In macrophage cultures, as well as upon implantation, a surface erosion process is observed for the amorphous (co)polymer networks, while an abrupt decrease in the rate and a change in the nature of the erosion process are observed with increasing crystallinity. These resorbable and form-stable networks with tuneable properties may find application in a broad range of biomedical applications.

Resorbable poly(trimethylene carbonate-co-ε-caprolactone) networks with a wide composition range are prepared by γ-irradiation of the corresponding linear polymers. It is shown that the network composition has a large effect on the mechanical properties as well as on the erosion behavior. These biocompatible networks are suitable for a variety of applications in medicine such as in drug delivery and tissue engineering.

Well-defined amphiphilic linear-dendritic prodrugs (MPEG-b-PAMAM-DOX) are synthesized by conjugating doxorubicin (DOX), to MPEG-b-PAMAM through the acid-labile hydrazone bond. The amphiphilic prodrugs form self-assembled nanoparticles in deionized water and encapsulate the hydrophobic anticancer drug 10-hydroxycamptothecin (HCPT) with a high drug loading efficiency. Studies on drug release and cellular uptake of the co-delivery system reveal that both drugs are released in a pH-dependent manner and effectively taken up by MCF-7 cells. In vitro methyl thiazolyl tetrazolium (MTT) assays and drug-induced apoptosis tests demonstrate the HCPT-loaded nanoparticles suppress cancer cell growth more efficiently than the MPEG-b-PAMAM-DOX prodrugs, free HCPT, and physical mixtures of MPEG-b-PAMAM-DOX and HCPT at equivalent DOX or HCPT doses.

A co-delivery system is prepared by loading 10-hydroxycamptothecin in self-assembled nanoparticles of acid-liable MPEG-b-PAMAM-DOX prodrugs. The use of inert carrier materials is reduced remarkably and the drug loading content is greatly increased. Moreover, enhanced anticancer efficiency is achieved, benefitting from the synergistic anticancer effects of the two drugs released from the co-delivery system.

A robust and effortless procedure is presented, which allows for the microstructuring of standard cell culture dishes. Cell adhesion and proliferation are controlled by three-dimensional poly(ethylene glycol)-dimethacrylate (PEG-DMA) microstructures. The spacing between microwells can be extended to millimeter size in order to enable the combination with robotic workstations. Cell arrays of microcolonies can be studied under boundary-free growth conditions by lift-off of the PEG-DMA layer in which the growth rate is accessible via the evolution of patch areas. Alternatively, PEG-DMA stencils can be used as templates for plasma-induced patterning.

Three-dimensional PEG-DMA microstructures on standard cell culture dishes allow arraying of microcultures. Widely spaced microwells are achieved by insertion of micropillars. Lift-off enables observation of freely proliferating cell patches and the growth rate is accessible via the evolution of patch areas. Furthermore, cells can be separated by plasma-induced micropatterning in which PEG-DMA stencils act as templates.

In spite of their attractive features, widespread biomedical applications of CS nanoparticles are yet to be realized due to their poor stability in physiological conditions, such as in buffer system at pH 7.4. Buffer-stable chitosan-based hybrid NPs (HNPs) are reported and characterized. Buffer stability is achieved by introducing polyglutamic acid to chitosan. The effect of PGA to CS molar ratio and crosslinking on HNP integrity, buffer stability, and biodegradability are studied. Preliminary in vitro studies are carried out to evaluate targeted uptake efficiency of folate conjugated HNPs. Successful demonstration of buffer stability and cancer cell targeting by HNPs achieves important milestones for chitosan-based nanoparticle technology.

In the presence of negatively charged polyglutamic acid, the pK_a of chitosan shifts to a higher value, increasing the degree of ionization of amine groups and the local charge density. The complex thus formed between chitosan and polyglutamic acid is stable in deionized (DI) water and also in the presence of salts such as in the case of PBS.

A set of thermoplastic polyurethanes is synthesized, combining undecylenic acid-derived telechelic diols as soft segments and 1,4-butanediol/4,4′-methylenebis(phenylisocyanate) as a hard segment (HS). These polymers are fully chemically and physically characterized by means of NMR and Fourier transform IR (FTIR) spectroscopy, size-exclusion chromatography (SEC), DSC, thermogravimetric analysis (TGA), tensile testing, and contact angle measurements. The obtained results reveal that both the molecular weight of the diol and the HS content greatly influence the physical and mechanical properties of these polymers. In addition, given the potential use of these materials for biomedical applications, hydrolytic degradation, their biocompatibility using a human fibroblast cell line, and performance as drug delivery carriers are evaluated.

Telechelic oligodiols based on undecylenic acid as a renewable resource are used as soft segments (SSs) for the synthesis of segmented polyurethanes. The molecular weight of the diol and the hard segment (HS) content dictate the microphase separation of the polyurethanes and their properties. The biocompatibility and drug release profiles of these polyurethanes make them well suited as sustained delivery carriers of hydrophobic drugs.

A new type of fluorescent polymeric micelles is developed by self-assembly from a series of amphiphilic block copolymers, poly(ethylene glycol)-b-poly[styrene-co-(2-(1,2,3,4,5-pentaphenyl-1H-silol-1-yloxy)ethyl methacrylate)] [PEG-b-P(S-co-PPSEMA)]. Their capability of loading doxorubicin (DOX) is investigated by monitoring the loading content, encapsulation efficiency, and photophysical properties of micelles. Förster resonance energy transfer from PPSEMA to DOX is observed in DOX-loaded micelles, which can serve as an indication of successful encapsulation of DOX in these micelles. The application of this new type of fluorescent polymeric micelles as a fluorescent probe and an anticancer drug carrier simultaneously is explored by studying the intracellular uptake of DOX-loaded micelles.

Fluorescent polymeric micelles with aggregation-induced emission properties are utilized as a fluorescent probe and an anticancer drug carrier simultaneously. The Förster resonance energy transfer from the micelles to the drugs facilitates the indication of successful encapsulation and subsequent release of DOX in these micelles.

Synthesis and characterization of a pH- and redox-sensitive hydrogel of poly(aspartic acid) are reported. Reversible gelation and dissolution are achieved both in dimethylformamide and in aqueous medium via a thiol-disulphide interconversion in the side chain of the polymers. Structural changes are confirmed by Raman microscopy and rheological measurements. Injectable aqueous solutions of thiolated poly(aspartic acid) can be converted into mechanically stable gels by oxidation, which can be useful for drug encapsulation and targeted delivery. Reduction-facilitated release of an entrapped drug from disulphide cross-linked hydrogels is studied.

The synthesis of pH- and redox sensitive hydrogels with a reversible response is reported. Mechanically stable poly(aspartic acid) gels form in aqueous solution when exposed to oxidation. The structural changes occurring in the sol–gel–sol transition are characterized by NMR spectroscopy, Ellmann's assay, Raman spectroscopy, and rheometry. Reduction-facilitated release of an entrapped drug is also demonstrated.

A series of nanoparticles is prepared via layer-by-layer assembly of oppositely charged, synthetic biocompatible polyamidoamine polymers as potential carriers. Particle size, surface charge and internal chain mobility are quantified as a function of the polymer type and number of layers. The effect of addition of surfactant is examined to simulate the effects of nanoparticle dissolution. The cyctotoxicity of these particles (in epithelia and murine cell lines) are orders of magnitude lower than polyethyleneimine controls. Stable nanoparticles may be prepared from mixtures of strongly, oppositely charged polymers, but less successfully from weakly charged polymers, and, given their acceptable toxicity characteristics, such modularly designed constructs show promise for drug and gene delivery.

A series of designer nanoparticles prepared via a layer-by-layer assembly of oppositely charged, synthetic biocompatible polyamidoamine polymers shows promise as potential carriers for genes and proteins. The particle size, surface charge, and internal chain mobility can be tailored by a judicious choice of polymer type and number of layers.

A well-defined amphiphilic polypeptide, poly(glutamic acid)₂₂-block-poly(alanine)₈ (PGlu₂₂-b-PAla₈), which plays the roles of both soluble (functional) additive and insoluble (structural) matrix, is employed to mediate the mineralization of CaCO₃ at the air/water interface. X-ray diffraction (XRD) and Raman spectroscopy, for example, show that the polymorph of CaCO₃ particles obtained is calcite. The observations from SEM and TEM suggest that PGlu₂₂-b-PAla₈ initiates the amorphous precursor phase and heterogeneous nucleation of CaCO₃ at the air/water interface, while temporarily stabilizes the gelatinous precursors as a process-directing agent; nevertheless, the initial concentration of Ca²⁺ controls the procedure of crystallization and the final morphology of CaCO₃ particles. Such “bifunctional” amphiphilic-polypeptide-regulated mineralization at the air/water interface may be applied to the synthesis of many kinds of symmetrical inorganic/organic hybrids.

A well-defined amphiphilic polypeptide, poly(glutamic acid)₂₂-block-poly(alanine)₈ (PGlu₂₂-b-PAla₈) is taken as organic additive to mediate the mineralization of CaCO₃. Asymmetrical calcite particles with various shapes are obtained at the air/water interface and PGlu₂₂-b-PAla₈ acts as a bifunctional template in the mineralization process according to time-dependent observations.

Two different composite scaffolds, solid-freeform-fabricated PCL/β-TCP supplemented with and without collagen nanofibers are fabricated. These scaffolds are evaluated whether a combination of collagen nanofibers with PCL/β-TCP can promote osteogenesis in a mastoid obliteration. To assess the effects of the cellular activities of osteoblast-like-cells (MG63), SEM images and MTT assays are conducted. Experimental mastoid obliteration is performed using guinea pigs that are divided group A (PCL/β-TCP/collagen-nanofiber scaffold) and group B (PCL/β-TCP scaffold). The results reveal that PCL/β-TCP/collagen scaffold provide much broader cell attachment sites than PCL/β-TCP scaffold. The µ-CT and fluorescent microscopy results reveal that the acceleration of early new bone formation within the pores and scaffold itself at week 4 post-operation is more effective in group A. In addition, based on the results of the histological and µ-CT at 12 weeks post-surgery, the effective regeneration of bone in the PCL/β-TCP/collagen scaffold is appeared.

A composite consisting of a solid freeform-fabricated PCL/β-TCP structure supplemented with electrospun collagen nanofibers is proposed to promote new bone formation for mastoid obliteration. The PCL/β-TCP/collagen-nanofiber scaffold provides much-broader cell attachment sites and faster new bone formation than a PCL/β-TCP scaffold.