Biogenic Gold Nanoparticle‐Based Antibacterial Contact Lenses for Color Blindness Management

Biogenic gold nanoparticles (BAu NPs) synthesized using olive leaf extract were used as an additive in commercial contact lenses (BAu lens). Their antibacterial and color blindness‐correcting properties were examined. To compare the properties, gold nanocomposite contact lenses were also synthesized using the well‐known Turkevich method (TAu lens). The breath‐ in/breath‐out method was used to load the Au NPs onto commercial contact lenses. The bio‐gold nanoparticles showed good dispersion and stability within the lens hydrogel matrix. Nanoparticle loading had a negligible effect on the contact lenses’ wettability and swelling properties. BAu lens filtered around 55% of visible light at 530 nm, a problematic wavelength for color blind patients. The optical filtering results were comparable with Pilestone commercial color blind correction glasses. BAu lenses also showed superior resistance against the attack of Pseudomonas aeruginosa and Staphylococcus aureus bacteria as compared to Tau lenses. As scanning electron microscopy (SEM) imaging showed, the BAu lenses showed a complete lack of surface attachment toward the bacterial colonies. This research provides a cost‐effective and scalable method of producing multi‐functional nanocomposite contact lenses with antibacterial and color blind correction properties.


Introduction
Contact lenses made of polymer hydrogels have been used daily by millions of consumers worldwide. [1]Some are used for correcting vision deficiencies, while others are used for aesthetic purposes and therapeutics.Despite the benefits, prolonged lens wear is associated with different types of microbial keratitis (MK) like bacterial keratitis (BK) and Acanthamoeba keratitis. [2,3]So, developing contact lenses with intrinsic antibacterial properties is essential while correcting vision deficiencies.
Contact lens wearing usually disengages the protective mechanism of the cornea that effectively prevents microbial infections.They also act as a template for bacterial growth by providing surface adhesion and biofilm formation.Contact lenses cover the eye suppressing the flow of antimicrobial tear fluid and causing hypoxia, which increases the microbial infiltration of the eyes. [4]Lens surfaces can enhance the production of biofilms with high bacterial density while effectively preventing high antibiotic dosages by forming protective polysaccharide bacterial films.2-Hydroxyethyl methacrylate contact lenses are the most prone to biofilm formation and bacterial adhesion. [5]S. aureus and P. aeruginosa bacterial strains are generally associated with a high incidence of bacterial keratitis (BK).Even though various approaches [6] have been used to eliminate bacterial growth on contact lens surfaces, the proliferation and severity of BK are still significant challenges for healthcare professionals worldwide. [7]he olive plant (olea europea) has been widely used as a nutritional source, herbal medicine, and antimicrobial agent throughout the Mediterranean region.Passed through oral and later as written traditions through different generations, the first formal study on the medicinal properties of olive leaf extract was published in 1854 to treat malaria and fever. [8]Olive leaf has antimicrobial compounds that prevent infection-causing mycoplasma, fungi, and bacteria while providing excellent anti-inflammatory and antioxidant properties.These properties are supplied by phytophenolic compounds called oleuropein and its derivatives found in the leaf extract. [7]This secoiridoid constitutes about 9% of the dry weight of the leaf.Both oleuropein and its degradation product hydroxytyrosol are known for their antioxidant and antibacterial properties. [9]During nanoparticle synthesis in olive leaf media, these compounds attach to the nanoparticles' surface, giving them stability, antimicrobial, and anti-inflammatory properties.The specific attachment of oleuropein to nanoparticles synthesized with olive leaf extract is due to a combination of factors, including the unique chemical properties of oleuropein, the conditions of the synthesis process, and the interactions between the active ingredients and the nanoparticle surface.Rajan et al. [10] used areca catechu nut for synthesizing gold nanoparticles (Au NPs) using microwave irradiation.The synthesized nanoparticles showed broad spectrum antibacterial properties along with low toxicity.Au NPs synthesized using mangifera indica seed showed excellent antibacterial properties against both gram negative and gram positive bacteria. [11]Here, we have used olive leaf extract to synthesize Au NPs and incorporated them as additives in commercial soft contact lenses to inhibit bacterial keratitis.Using a biological medium for synthesizing Au NPs prevented the use of cytotoxic chemicals in nanomaterial synthesis. [12]The imbibed Au NPs present color-filtering properties (due to surface plasmons) and may also help manage color blindness and related ocular conditions. [13,14]Color blindness is an inheritable disorder affecting 5-10% of males and 0.5-1% of female populations. [15]Even though no known cure for color blindness exists, patients use different management techniques to improve their color perception.Several companies manufacture tinted glasses that can filter out specific wavelengths of light, helping color-blind patients in their color perception. [16,17]hese color-corrective glasses are ineffective with other visioncorrecting treatments and uncomfortable to use because of their bulkiness despite being expensive. [18]u NP-loaded contact lenses have been studied for different applications like drug delivery, [19][20][21] color blindness, [14,22] and functional therapeutics. [23,24]Herein, we report a facile method for fabricating nanocomposite lenses based on biosynthesized Au NPs (using olive leaf media) for antibacterial and color blindness management applications.For comparison purposes, nanocomposite contact lenses were also produced using Au NPs synthesized from the commonly employed Turkevich method. [25]All nanocomposite lenses were synthesized by doping commercial contact lenses using the unique breath-in/breath-out method for fabricating Au NP-loaded contact lenses. [26]The concentration of Au NPs within the lenses was altered by changing the number of breath-in/breathout cycles.The nanocomposite lenses and related materials were tested for their morphological and optical properties using the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) along with Fourier-transform infrared (FTIR) and ultraviolet-visible (UV-Vis) spectroscopies.To the best of our knowledge, no research has been conducted on the effect of Au NP loading on contact lenses' antibacterial surface adhesion properties.

Synthesis of Gold Nanoparticles Using Olea Europa Extract
The olive leaves were washed thoroughly using DI water to remove impurities.They were air-dried and grounded before dispersing them into 100 mL De-ionized water, upon which they were constantly stirred for 30 min at 80 °C.The filtered liquid was then used for the preparation of gold nanoparticles (BAu NPs).Generally, 2 g of HAuCl 4 salt was dispersed in 50 mL DI water under constant stirring at 80 °C.30 mL of olive leaf extract was added to the mix and stirred for 30 min.The reaction was completed by adding 10 mL of lemon juice and heating it in a microwave reactor for 60 s at 80 °C.The solution was centrifuged to get the required Au NP concentrations.The procedure is illustrated in Figure 1a.More details on the synthesis technique and the quality of the Au NPs synthesized can be found from Ref. [27].

Synthesis of Gold Nanoparticles by the Turkevich Method
This method involves the reduction of chloroauric acid using sodium citrate as the reducing agent.In a typical procedure, 50 mL of 0.25 mM gold chloride solution is brought to a boil in a double-walled reactor heated by a bath thermostat.Using a mantle ensures a homogeneous temperature distribution within the reaction solution.The solution is vigorously stirred using Teflon-coated magnetic bars.Then, a preheated citrate solution of 34 mM concentration is added to the boiling gold solution.After 15 min, the liquid is extracted and cooled to room temperature.No refluxing is utilized in this method to prevent the presence of temperature gradients in the fluid.This can help ensure that the resulting nanoparticles are consistent in size and shape. [28]The procedure is illustrated in Figure 1b.

Gold Nanocomposite Lens Synthesis by Chemical Volumetric Modulation
The breath-in/ breath-out method was utilized to incorporate the nanoparticles into the commercial contact lenses.The Acuvue lenses were soaked in 10 mL of acetone for two min, followed by a soak in 10 mL of colloidal Au NPs.This process was repeated to ensure enough loading of the nanoparticles into the contact lens' gel matrix.After soaking, the lenses were washed with deionized water to remove any excess colloidal solution on the surface.The samples were stored in a contact lens solution at 25 °C for further analysis.The process is illustrated in Figure 1c.This process of adding nanoparticles to the gel involves two stages.Firstly, the swollen gel is immersed in a solvent that lacks a proton and loses water, making it smaller (breath out).Secondly, the shrunken gel is placed in a solution containing nanoparticles, allowing it to absorb them (breath in).When the gel is exposed to the solvent again, the nanoparticles remain embedded in the gel matrix.

Bacterial Preparation and Inoculation
For measuring the antimicrobial properties of the contact lenses, bacterial strains S. aureus and P. aeruginosa were cultured in a LB for 24 h at 37 °C in a shaker.Contact lenses from the lens packet (clear and undoped) and lenses doped only in acetone and water were used as a control in the experiment.They were washed with ethanol to remove any contaminating bacteria on the surface.The lenses were cut into two, and each part was used for each strain of bacteria.The lenses were placed into well culture plates.The wells in the dish had 10 mL of LB in them. 1 mL of (1.0 Â 10 6 cfu mL À1 ) bacterial solution was added.The well plates were shaken for 15 min before placing them in an incubator for 8 h at 37 °C.After 8 h, the well plates were removed from the incubator, and further processing was done to study the effect of bacteria on the lens surfaces.The process is illustrated in Figure 1d.

Bacterial Fixation for SEM
The following protocol was used to study the surface attachment of bacteria on the contact lens surface.The lenses were removed from the bacterial inoculum and washed with sterile PBS to remove any excess bacteria.10 mL of 0.1 mM glutaraldehyde in PBS solution was added.The full coverage of the lens' surface was ensured.This solution was kept in the fridge overnight at 4 °C.Then, the lens was removed from the solution, and it underwent a series of dehydration steps, with 10-100% ethanol solutions.The lenses were kept in 100% ethanol until the SEM studies were conducted.After mounting the lens onto an aluminum SEM stub and the surface was sputter-coated with gold thin film, to perform the imaging analysis.The procedure is illustrated in Figure 1e.

Analysis
The transmission spectra of both types of nanoparticles were obtained using a UV-Vis spectrophotometer USB 2000þ through OceanView software.Tecnai TEM 200 kV was used to monitor the synthesized nanoparticles' morphology.Malvern DLS Zeta sizer was utilized to understand the zeta potential and the size of nanoparticles.Bruker Vertex 80v FTIR was used to study the functional groups on the lens.Wettability properties of the contact lenses were assessed by measuring their static contact angle.The hydrated contact lenses were placed on a glass slide, and the sessile drop method was used to study the surface contact angle.Water drops of 3, 5, and 10 μL were placed on the lens surface, and the contact angle resolved images were captured.The contact angle was detected using ImageJ software with an external plug-in, "LBADSA."Swelling due to hydration of contact lenses was measured by recording their weight change over time upon dehydrating them for 2 h at 80 °C.The SEM-EDS measurements and mapping were conducted after gold coating the samples before the examination.

Results and Discussion
Figure 2a,b shows the TEM images of the BAu and TAu NPs, respectively.The average size of the nanoparticles was 10 nm for both TAu NPS and BAu NPs, and they exhibit a spherical morphology.The nanoparticles formed from the Turkevich method are more uniform than biosynthesized nanoparticles.This was because of the strong interaction between the surface of the nanoparticles and the biomolecules, which prevents the embryonic nanoparticles from agglomerating to form larger nanoparticles. [29]Figure 2c,d shows the size distribution histograms of the nanoparticles as measured by DLS Zetasizer.The sizes of the particles recorded by DLS Zetasizer were larger and more dispersed than the TEM results.In the case of the BAu NPs, the large size may include the organic compounds from the olive leaf extract attached to the surface of Au NPs.The microwave-assisted synthesis technique ensured the maximum level of phenol group attachment without any decay attached to the Au NP. [30] In the colloidal solution, there may be different forces like van der Waals forces that interact the nanoparticles, leading to increased nanoparticles' size.
Figure 2c shows the mechanism of organic group capping of Au NPs.The biogenic synthesis of Au NPs is well-established. [31]n short, the organic compounds from the olive leaf extract, namely, oleuropein and hydroxytyrosol, attach to the atomic surface during the reduction.This prevents the agglomeration of the molecules.Figure 2d shows the UV-Vis spectrum analysis of the BAu and TAu NPs.As shown in the inset, both solutions offer an intense magenta color.This color results from the interaction between the incoming electromagnetic field and the collective oscillation of the free conduction electrons called surface plasmon resonance (SPR).This phenomenon can further be elucidated by UV-Vis spectrum analysis.Both samples showed an absorbance peak at 530 nm.However, TAu NPs showed a broader peak, indicating the aggregation of particles in the colloidal matrix.This happens as adjacent nanoparticles get agglomerated and share the conduction electrons requiring less energy for the resonance excitation.Dipole-dipole interaction between neighboring nanoparticles also could lead to the broadening of the absorbance peak. [32]igure 3a,b show the transmittance spectra of the BAu and TAu NP-loaded lenses, respectively, with respect to number of breath-in/breath-out cycles.With the increase in cycles, the transmittance percentage decreased for both samples.Both samples showed a transmittance dip at around 530 nm.This increase in transmittance (more absorption) dip can be attributed to the bonding of Au NPs with the polymer's electron-rich oxygen and nitrogen species, which indicates the entrapped nanoparticles did not escape the polymer matrix subsequent to each breath-out cycle.At 12 cycles, the transmittance dip of around 45% can be observed for the BAu lens, while it was about 60% for the TAu lens.Moreover, the latter demonstrates the enhanced filtering ability of the BAu lens, to block out the problematic wavelengths for color blindness management.With increasing cycles, the BAu lens shows a red shift, while the TAu lens shows a slight blue shift.The shift of wavelength to longer wavelengths results the agglomeration or quantum confinement effect. [33]Red shift is the result of reduced interparticle distance between Au NPs as more Au NPs enter the lens. [34]The plasmonic shift is only 1-2 nm after the 9th cycle for both BAu and TAu lenses, indicating the stabilization of nanoparticles embedded in the lens.
It is necessary to block the visible wavelengths between 540-580 nm to enhance distinction in red-green color-blind patients. [34]Figure 3c shows the Au NP solution between successive cycles.TAu NPs solution shows agglomeration between cycles and reaches a size of 80 nm, as indicated by the violet color of the solution after 12 cycles.This might be due to the interaction between the acetone on the surface of the contact lens with the Au NP solution making it unstable.The spd orbital of the Au NPs could interact with the p orbital of the oxygen atom on the acetone creating a back bond. [35]Weak hydrogen bonds could also form between the gold atom and hydrogen in the acetone molecule. [35]Acetone also could remove the citrate surfactant on the TAu NPs and make them more vulnerable to agglomeration. Figure 3d shows the appearance of the nanocomposite contact lenses with increasing cycles.BAu lens offers more uniformity in the lens color formation.TAu lens has some agglomerated coloration on the lens' surface.This might be due to the agglomeration of NPs inside or outside the lens matrix.
The stability of the contact lenses was tested by measuring the transmittance peak over 14 days.BAu lens showed no significant difference in the transmission peak even after 14 days of continuous immersion in contact lens storage solution.This shows the stability of the Au NPs trapped within the nanocomposite contact lens (Figure 4).
Hydrogel matrices' morphology and functionalization were examined using SEM and FTIR.images along with EDX mapping of BAu and TAu lens surface respectively.The SEM results show that the TAu lens has larger particles while the BAu lens has smaller particles distributed throughout the lens matrix.The average size of TAu NPs was 500 nm, while BAu NPs retained their original size of 20 nm within the hydrogel matrix.The agglomeration of TAu NPs within the matrix and the solution due to acetone interaction resulted in the larger size of TAu NPs.EDX results show a uniform and homogenous distribution of BAu NPs across the contact lens matrix.FTIR spectra (Figure 5e) show multiple bands at 3420 (O-H stretching) and 1721 cm À1 (─C═O stretching).The band at 1467 cm À1 is described by C─H bending.The bands between 2710 and 2900 cm À1 can be ascribed to C─H stretching for methylene ─CH 2 and methyl ─CH 3 groups.The absorption peak at 1620 cm À1 can be dedicated to ester carbonyl (C═O) groups.The peaks at 1261, 1625, and 1721 cm À1 can be ascribed to the C─N stretch, C═C stretch, and C═O stretch, respectively. [36]The amide groups represent protein secondary structures.The peak at 3420 cm À1 is attributed to OH stretching and shows an increase in peak intensity and a slight red shift with the attachment of Au NPs.The presence of coordination sites for metal ions is suggested by the observation of OH bonds in the FTIR spectra.In this case, the change in the intensity and peak of OH bonds in the spectra can be attributed to the attachment of Au NPs to the contact lens matrix.Generally, alterations in IR spectra, such as shifts in characteristic bands or their disappearance, are noted during complexation processes or when adsorbed onto nanoparticle surfaces. [37]BAu lens offers higher intensity and peak shifting compared to the TAu lens.This might be due to the better attachment of BAu NPs to the hydrogel matrix and the higher concentration of BAu NPs in the polymer matrix. [5]The FTIR results indicate the successful grafting of BAu and TAu NPs to the commercial hydrogel matrix.The AU NPs are sorted and trapped within the polymer matrix.
Figure 5f shows that the BAu NPs loaded contact lens filtered light at similar wavelengths to the commercial Pilestone glasses (used for color-blindness correction), indicating its efficacy as a color-blind wearable aid.The contact angle of a soft contact lens can be used to measure the wettability of the lens' material, which can affect the comfort and visual acuity of the lens.The contact angle of a soft contact lens can vary depending on factors such as the material used to make the lens, the surface treatment of the lens, and the presence of any coatings or other additives on the lens surface.Generally, a lower contact angle indicates better wettability and improved comfort for the wearer. [38,39]Figure 6a,b demonstrate the contact angle of BAu and TAu NPs loaded contact lenses along with a clear contact lens.Contact angle measurements of the three contact lenses were between 75°and 78°.As expected, differences among the three lenses are very insignificant to suggest any specific trend.Figure 6c presents the measured water retention of the various contact lenses developed.Water retention is an essential characteristic of contact lenses that can affect their comfort, stability, permeability, and optical properties.The amount of water retained by the lens material can affect the lens's oxygen permeability or the amount of oxygen that can pass through the lens to reach the cornea.Higher water retention can improve oxygen permeability, improving the cornea's health and reducing the risk of complications such as hypoxia.Water retention can also affect the mechanical properties of the lens, such as its flexibility and durability.A lens with high water retention may be more flexible and conformable to the shape of the eye, which can improve comfort for the wearer. [40]BAu and TAu lenses exhibit lower water retention compared to plain lenses.This might be due to the occupation of Au NPs on the contact lenses' interstitial space, which reduced its ability to absorb water. [41]However, the change in water retention needs to be more significant to irritate the wearers.Salih et al. [42] in their work had determined that the breath-in/breath-out method does not cause deterioration of the important material properties of the contact lens.
Furthermore, the mechanisms of bacterial and biofilm prevention are given in Figure 7a,b, respectively.SEM visualization of the sample's surface after bacterial incubation is shown in Figure 7c.BAu lens shows a significantly lower number of bacteria on the surface, both in the case of S. aureus and P. aeruginosa.The plain contact lens, acetone treated contact lens, and TAu lens showed a significant amount of closely attached biofilms and adherent bacterial cells.P. aeruginosa formed polymeric biomaterials that spread with interconnected mesh like structures throughout the surface.They also formed multilayer rod-shaped colonies that varied in length and shape.S. aureus, however, did not show any biofilm formation on the surface of the contact lenses.They were distributed throughout the surface as single cells.Pseudomonas aeruginosa is one of the well-known culprits for forming bacterial ulcers in contact lens wearers.They attach to the cornea using special receptors at the outer cell membrane, causing infections.They also show high virulence due to different toxins, flagella, and adhesins forming on their attachment surface. [5]Some strains also cause antibiotic metabolism reducing the effect of antibiotics.Bacterial biofilm formation is associated with the need for a high amount of antibacterial dosage to break through the formidable lipid-lipid barrier in the films.This also enables them to survive in hostile environments caused by immunity, antibiotics, shear forces, etc.; thus, eradicating them becomes more complex. [5]The SEM images of the BAu lenses showed lower biofilm thickening and a more transparent surface.
The antibacterial efficacy of the BAu lens against bacterial infection might be due to a synergistic effect of phenolic compounds attached to the surface of the Au NPs and the size of entrapped Au NPs in the lens.The exact mechanism of olive polyphenols on bacteria currently is yet to be completely understood.However, several studies have found the efficacy of these compounds to inhibit lysozymes, micrococci nuclease, and different enzymes, thus slowing down the growth rate of microbes.Baycin et al. [43] documented the efficiency of olive phenols against S. aureus and P. aeruginosa bacteria.Their study showed a selectivity of extracts toward gram-positive bacteria.Pereira et al. [44]   also found the antibacterial activity of olive leaf extract against S. aureus and P. aeruginosa.They did not observe any selectivity between gram-positive and gram-negative bacteria.The extracts affected the permeability of the cell membrane of the bacteria by denaturing the proteins on bacterial cells. [45,46]In another study, Mostafa et al. [7] documented the efficacy of olive leaf extract-doped Ag NPs in preventing bacterial infection.They demonstrated the effect of thiol molecules on inhibiting the bacteria's respiratory enzymes, slowing down their cellular metabolism and eventual cell death.Au NPs at the nanoscale level have unique and beneficial properties that make them effective against microbes.
Gold is a very stable metal with non-toxic and biocompatible properties, and it can bind to many different types of ligands.The large specific surface area of Au NPs provides numerous sites for binding with target bacteria.As a result, they have a broad antibacterial spectrum that works against gram-positive and gramnegative bacteria.Additionally, they are less likely to develop drug resistance compared to standard antibiotics because they target multiple molecules within bacteria, making it difficult for bacteria to defend against all damage.The main mechanisms through which antibacterial effects are achieved involve causing harm to the outer membrane and biofilms, generating reactive oxygen species (ROS), and discharging metal ions that cause damage to bacterial cells.The smaller size of NPs in the BAu lens resulted from the encapsulation of olive oil extract on the surface.Its stability could also increase its interaction with the bacterial cells, increasing its inhibitory effects.The effectiveness of NPs in their ability to fight against bacteria is significantly impacted by their size and how well they can disperse.The rule that applies to silver NPs, where smaller size leads to better antibacterial effects, also applies to Au NPs. [47]Vanaraj et al. [48] showed 92% efficiency of biogenetic Au NPs against biofilm formation in P.aerugionosa.Hoa et al. showed their activity against S. aureus. [49]In fact, as the size of NPs decreases below 10 nm, the proportion of surface atoms increases rapidly.These atoms on the surface are highly active and tend to stabilize by binding with other particles.Aggregation of NPs reduces their contact area with bacteria, which can weaken their antibacterial properties.Some studies have also shown that small Au NPs can enter cells by binding to the pore proteins and changing the porin pathway. [50]herefore, decreasing the particle size and increasing monodispersity can enhance the antibacterial properties of NPs.
The antibacterial mechanism of Au NPs can be explained in five different pathways.Primarily, the smaller-sized NPs can break the cell wall.BAu lens, which has small particles, could use this as a bactericidal mechanism.Secondly, smaller NPs could cause cell wall rupture, while larger NPs could cause lysis and cell death.Thirdly, gold nanoparticles could use cytomembrane and their intramembrane action to prevent bacterial growth.Fourthly, Au NPs and the oleuropein that entered the cytoplasm of the cells could form ROS that could cause DNA denaturation, protein denaturation, and enzyme disruption.All of these lead to cell death.Finally, NPs and oleuropein getting attached to the ribosome and mitochondria will also cause cell destruction.This multi-action model of biogenetic gold nanoparticles on the bacterial cell is described in Figure 7a.The NPs and the ROS could also disrupt biofilm formation and adhesion, as given in Figure 7b.As such, the instability, low surface area, and large particle size of the TAu NPs prevented them from significantly inhibiting bacterial growth.At the same time, the synergetic action of polyphenols on the surface of gold nanoparticles and their size stability inside the lens matrix helped the BAu lens to have a highly enhanced protective activity against infection-causing bacteria.Hence, the fabrication of such a lens allows for intrinsic bactericidal action along with its potential utilization as color blind wearable aid.

Conclusion
Utilizing olive leaf-assisted synthesis of Au NPs and incorporating them into contact lenses, we have demonstrated the antibacterial and color blind enhancing properties of these nanocomposite contact lenses.The olive oil compounds got attached to the surface of the NPs, providing high stability for the NPs within the contact lens matrix.It also helped them to form a uniform dispersion within the hydrogel.The lenses showed a 55% transmission loss at 530 nm, a problematic visible wavelength for the red-green color-blind patients.The results were comparable to commercial Pilestone glasses.The lenses were further explored for their antibacterial properties.Due to the synergetic effect of olive leaf phytophenolic compounds attached to the Au NPs and the small size of Au NPs, biofilm formation, and bacterial attachment onto the lens' surface were prevented.The method of antibacterial action of Au NPs proceeds in different mechanisms, namely ROS generation, damage of the cell walls and cell membrane by the NPs, and the attachment of Au NPs and oleuropein on the ribosome and mitochondria of the cell, which eventually leads to cell death.This study could be used as a foreground for the efficacy of biogenic metallic NPs as an additive in commercial contact lenses for a myriad of applications.

Figure 1 .
Figure 1.a) Schematics of the synthesis method of Bio-gold nanoparticles from olive leaf extract.b) Schematics of Turkevich method used for Au NP synthesis.c) Breath-in/Breath-out method for Au NP loading into commercial contact lenses.d) Bacterial inoculation of contact lenses and incubation.e) Fixation of bacteria on the contact lens surface.

Figure 2 .
Figure 2. a) TEM image of BAu NPs.b) TEM image of TAu NPs.The scale bars represent 20 nm.c) Schematics of the formation of BAu NPs.d) DLS particle size histogram of BAu NPs.e) DLS particle size histogram of TAu NPs.f ) UV-Vis spectra of BAu and TAu NPs.The images of the colloidal solutions of the NPs are shown in the inserts.
Figure 5a-d show the SEM

Figure 3 .
Figure 3. a) UV-Vis transmission of BAu lens with increasing number of breath-in/breath-out cycles.b) UV-transmission spectra of TAu NPs concerning several cycles.c) Gold NPs solution after cyclic breath-in/breath-out NP doping.d) The contact lenses changing visible coloration after breath-in/breathout cycles.The diameter of the lens is 14.3 mm.

Figure 4 .
Figure 4. a) Stability of BAu lens over 2 weeks.b) Stability of TAu lens over a period of 2 weeks.c) BAu lens' appearance over a period of 2 weeks.d) TAu lens' appearance over a period of 2 weeks.All the lenses have a diameter of 14.3 mm.e) Max transmission at 530 nm vs number of breath-in/breath-out cycles.f ) Max transmission at 530 nm vs storage time for a period of 2 weeks.

Figure 5 .
Figure 5. a) BAu NPs dispersed in the contact lens.b) TAu NPs dispersed in the contact lens matrix.Scale bars represent 1 μm.c) EDX mapping of BAu NPs distribution in the contact lens.d) EDX mapping of TAu NPs distribution in the contact lens.e) FTIR spectra of clear and gold NPs loaded contact lens.f ) Comparison of BAu lens with commercial Pilestone glasses.

Figure 6 .
Figure 6.a) Contact angle of BAu and TAu lens at 3, 5, 10 μm water droplet dispersion.Scale: 1 mm.b) Contact angle for the lenses at different water droplet quantities.c) Swelling or water content of the lenses for 1 h duration.

Figure 7 .
Figure 7. a) Mechanism of bacterial inhibition in the BAu lens.The BAu NPs enter through porin proteins and cause the generation of reactive oxidative species (ROS) damaging RNA, enzyme and protein denaturation.NPs and oleuropein can cause ribosome and mitochondrial damage.NPs accumulation can cause cell wall and cell membrane damage and cytoplasm leakage.Phosphate, glutamate, and potassium from oleuropein cause metabolic damage in the cell.b) Mechanism of biofilm inhibition by the BAu lens.c) SEM images of the surface adhesion of S. aureus and P. aeruginosa bacteria for clear, acetone doped, Tau, and BAu lenses.All scale bars are given at 1 μm.