Surface Immobilization of Nano-Silver on Polymeric Medical Devices to Prevent Bacterial Biofilm Formation

Nanohydroxyapatite Coating Attenuates Fibrotic and Immune Responses to Promote Keratoprosthesis Biointegration in Advanced Ocular Surface Disorders

Keratoprosthesis (KPro) implantation is frequently the only recourse for patients with severe corneal disease. However, problems arise due to inadequate biointegration of the KPro, particularly the PMMA optical cylinder, such as tissue detachment, tissue melting, or eye-threatening infection in the interface. Here, using the AuroKPro as a model prosthesis, a surface functionalization approach─coating the optical cylinder with nanohydroxyapatite (nHAp)─was trialed in rabbit eyes with and without a proceeding chemical injury. In chemically injured eyes, which simulated total limbal epithelial stem cell deficiency, clear benefits were conferred by the coating. The total modified Hackett-McDonald score and area of tissue apposition differences 12 weeks after implantation were 5.0 and 22.5%, respectively. Mechanical push-in tests revealed that 31.8% greater work was required to detach the tissues. These differences were less marked in uninjured eyes, which showed total score and tissue apposition differences of 2.5 and 11.5%, respectively, and a work difference of 23.5%. The improved biointegration could be contributed by the attenuated expression of fibronectin (p = 0.036), collagen 3A1 (p = 0.033), and α-smooth muscle actin (p = 0.045)─proteins typically upregulated during nonadherent fibrous capsule envelopment of bioinert material─adjacent to the optical cylinders. The coating also appeared to induce a less immunogenic milieu in the ocular surface tissue, evidenced by the markedly lower expression of tear proteins associated with immune and stimulus responses. Collectively, the level of these tear proteins in eyes with coated prostheses was 1.1 ± 13.0% of naïve eyes: substantially lower than with noncoated KPros (246.5 ± 79.3% of naïve, p = 0.038). Together, our results indicated that nHAp coating may reduce the risk of prosthesis failure in severely injured eyes, which are representative of the cohort of KPro patients.

The role of nanocomposites against biofilm infections in humans

The use of nanomaterials in several fields of science has undergone a revolution in the last few decades. It has been reported by the National Institutes of Health (NIH) that 65% and 80% of infections are accountable for at least 65% of human bacterial infections. One of their important applications in healthcare is the use of nanoparticles (NPs) to eradicate free-floating bacteria and those that form biofilms. A nanocomposite (NC) is a multiphase stable fabric with one or three dimensions that are much smaller than 100 nm, or systems with nanoscale repeat distances between the unique phases that make up the material. Using NC materials to get rid of germs is a more sophisticated and effective technique to destroy bacterial biofilms. These biofilms are refractory to standard antibiotics, mainly to chronic infections and non-healing wounds. Materials like graphene and chitosan can be utilized to make several forms of NCs, in addition to different metal oxides. The ability of NCs to address the issue of bacterial resistance is its main advantage over antibiotics. This review highlights the synthesis, characterization, and mechanism through which NCs disrupt Gram-positive and Gram-negative bacterial biofilms, and their relative benefits and drawbacks. There is an urgent need to develop materials like NCs with a larger spectrum of action due to the rising prevalence of human bacterial diseases that are multidrug-resistant and form biofilms.

Antibiofilm properties of silver nanoparticles incorporated into polymethyl methacrylate used for dental applications

BACKGROUND

Acrylic resins used in dental and biomedical applications do not have antimicrobial properties, their surface is susceptible to colonization of microorganisms.

OBJECTIVE

The aim of this study was to evaluate the antibiofilm properties of silver nanoparticles (AgNPs) deposited in a polymethyl methacrylate (PMMA) surface against a Staphylococcus aureus biofilm.

METHODS

The PMMA was impregnated with AgNPs by using the in-situ polymerization method. To determine the solubility of the incorporated silver (Ag+) atomic absorption spectrophotometry was used (AAS) at 24 h, 48 h, 7 days, and 30 days. Thirty specimens of PMMA with AgNPs and without NP (control group) were assembled in the CDC Biofilm Bioreactor system with a cell suspension of S. aureus. The specimens were removed at 6, 12, 24, 48, and 72 h to determine the viability profile and quantify the Arbitrary Fluorescence Units (AFU).

RESULTS

The AgNPs showed an irregular and quasispherical shape with an average size of 25 nm. AAS analysis demonstrated a low solubility of Ag+. The formation of the S. aureus biofilm increased as the evaluation periods continued up to 72 h. The experimental group showed poor growth, and a decrease in the intensity of the fluorescence demonstrated a statistically significant inhibition of the formation of the biofilm (P < 0.05) in relation to the control group at 6, 12, 24, 48, and 72 h.

CONCLUSION

AgNPs incorporated into PMMA decreased the growth and maturation of S. aureus biofilm.

Antibacterial and Antiviral Coating on Surfaces through Dopamine-Assisted Codeposition of an Antifouling Polymer and In Situ Formed Nanosilver

Bacteria and viruses can adhere onto diverse surfaces and be transmitted in multiple ways. A bifunctional coating that integrates both antibacterial and antiviral activities is a promising approach to mitigate bacterial and viral infections arising from a contaminated surface. However, current coating approaches encounter a slow reaction, limited activity against diverse bacteria or viruses, short-term activity, difficulty in scaling-up, and poor adaptation to diverse material surfaces. Here, we report a new one-step strategy for the development of a polydopamine-based nonfouling antibacterial and antiviral coating by the codeposition of various components. The in situ formed nanosilver in the presence of polydopamine was incorporated into the coating and served as both antibacterial and antiviral agents. In addition, the coassembly of polydopamine and a nonfouling hydrophilic polymer was constructed to prevent the adhesion of bacteria and viruses on the coating. The coating was prepared on model surfaces and thoroughly characterized using various surface analytical techniques. The coating exhibited strong antifouling properties with a reduction of nonspecific protein adsorption up to 90%. The coating was tested against both Gram-positive and Gram-negative bacteria and showed long-term antibacterial effectiveness, which correlated with the composition of the coating. The antiviral activity of the coating was evaluated against human coronavirus 229E. A possible mechanism of action of the coating was proposed. We anticipate that the optimized coating will have applications in the development of infection prevention devices and surfaces.

Durable Surfaces from Film-Forming Silver Assemblies for Long-Term Zero Bacterial Adhesion without Toxicity

The long-term prevention of biofilm formation on the surface of indwelling medical devices remains a challenge. Silver has been reutilized in recent years for combating biofilm formation due to its indisputable bactericidal potency; however, the toxicity, low stability, and short-term activity of the current silver coatings have limited their use. Here, we report the development of silver-based film-forming antibacterial engineered (SAFE) assemblies for the generation of durable lubricous antibiofilm surface long-term activity without silver toxicity that was applicable to diverse materials via a highly scalable dip/spray/solution-skinning process. The SAFE coating was obtained through a large-scale screening, resulting in effective incorporation of silver nanoparticles (∼10 nm) into a stable nonsticky coating with high surface hierarchy and coverage, which guaranteed sustained silver release. The lead coating showed zero bacterial adhesion over a 1 month experiment in the presence of a high load of diverse bacteria, including difficult-to-kill and stone-forming strains. The SAFE coating showed high biocompatibility and excellent antibiofilm activity in vivo.

Isolation and Propagation of Human Corneal Stromal Keratocytes for Tissue Engineering and Cell Therapy

The human corneal stroma contains corneal stromal keratocytes (CSKs) that synthesize and deposit collagens and keratan sulfate proteoglycans into the stromal matrix to maintain the corneal structural integrity and transparency. In adult corneas, CSKs are quiescent and arrested in the G0 phase of the cell cycle. Following injury, some CSKs undergo apoptosis, whereas the surviving cells are activated to become stromal fibroblasts (SFs) and myofibroblasts (MyoFBs), as a natural mechanism of wound healing. The SFs and MyoFBs secrete abnormal extracellular matrix proteins, leading to corneal fibrosis and scar formation (corneal opacification). The issue is compounded by the fact that CSK transformation into SFs or MyoFBs is irreversible in vivo, which leads to chronic opacification. In this scenario, corneal transplantation is the only recourse. The application of cell therapy by replenishing CSKs, propagated in vitro, in the injured corneas has been demonstrated to be efficacious in resolving early-onset corneal opacification. However, expanding CSKs is challenging and has been the limiting factor for the application in corneal tissue engineering and cell therapy. The supplementation of serum in the culture medium promotes cell division but inevitably converts the CSKs into SFs. Similar to the in vivo conditions, the transformation is irreversible, even when the SF culture is switched to a serum-free medium. In the current article, we present a detailed protocol on the isolation and propagation of bona fide human CSKs and the morphological and genotypic differences from SFs.

Antimicrobial Properties of Lepidium sativum L. Facilitated Silver Nanoparticles

Antibiotic resistance toward commonly used medicinal drugs is a dangerously growing threat to our existence. Plants are naturally equipped with a spectrum of biomolecules and metabolites with important biological activities. These natural compounds constitute a treasure in the fight against multidrug-resistant microorganisms. The development of plant-based antimicrobials through green synthesis may deliver alternatives to common drugs. Lepidium sativum L. (LS) is widely available throughout the world as a fast-growing herb known as garden cress. LS seed oil is interesting due to its antimicrobial, antioxidant, and anti-inflammatory activities. Nanotechnology offers a plethora of applications in the health sector. Silver nanoparticles (AgNP) are used due to their antimicrobial properties. We combined LS and AgNP to prevent microbial resistance through plant-based synergistic mechanisms within the nanomaterial. AgNP were prepared by a facile one-pot synthesis through plant-biomolecules-induced reduction of silver nitrate via a green method. The phytochemicals in the aqueous LS extract act as reducing, capping, and stabilizing agents of AgNP. The composition of the LS-AgNP biohybrids was confirmed by analytical methods. Antimicrobial testing against 10 reference strains of pathogens exhibited excellent to intermediate antimicrobial activity. The bio-nanohybrid LS-AgNP has potential uses as a broad-spectrum microbicide, disinfectant, and wound care product.

The combination of medical devices and medicinal products revisited from the new European legal framework

Medical devices and medicinal products have many similarities in their nature, scope or specific medical purposes, and despite the differences in their principal means of action, they are often used in combination. Indeed, many medicinal products depend on medical devices for their administration, and it is increasingly common for medical devices to contain medicinal substances to support their action. Therefore, the combination of medicinal products and medical devices provides additional benefits for patients. However, their higher technical complexity requires a strengthening of their authorisation and certification requirements. In this regard, more comprehensive requirements and classification rules are introduced by a new European regulation on medical devices that fully applies from May 26^th 2021. On account of their therapeutic significance, this review aims at gaining insight into the borderline between medical devices and medicinal products in this new 2021 regulatory framework. For the first time, any item containing a medical device and a medicinal product will have both parts evaluated. Through exemplification of both marketed and investigational devices incorporating medicinal substances and drug-device combinations, the new European requirements and their implications are thoroughly illustrated herein.

Enhanced Antibacterial and Anti-Biofilm Activities of Antimicrobial Peptides Modified Silver Nanoparticles

Background

The biofilms could protect bacteria from antibiotics and promote the production of drug-resistant strains, making the bacteria more difficult to be eradicated. Thus, we developed an AMP@PDA@AgNPs nanocomposite, which is formed by modifying silver nanoparticles (AgNPs) with antimicrobial peptides (AMP) modified nanocomposite to destroy biofilm in this study.

Methods

The AMP@PDA@AgNPs nanocomposite was prepared with polymerization method and characterized by using ultraviolet-visible (UV-vis) spectroscopy, dynamic light scattering (DLS), Fourier transform-infrared spectroscopy (FT-IR), and transmission electron microscope (TEM). The antibacterial effects of the nanocomposite were investigated by using agar diffusion method and minimum inhibitory concentration (MIC) test. The quantitative analysis of the biofilm formation by the nanocomposite was conducted using crystal violet staining and confocal laser scanning microscope (CLSM).

Results

The DLS and TEM analysis showed it was a spherical nanocomposite with 200 nm size and well dispersed . The results of UV-vis and FT-IR confirmed the presence of AMP and AgNPs. The nanocomposite had an excellent biocompatibility at 100 μg/mL. And the AMP@PDA@AgNPs nanocomposite showed superior antimicrobial activity against both Gram-negative (E. coli, P. aeruginosa) and Gram-positive (S. aureus) bacteria than AgNPs or AMP. Importantly, the mRNA expression of biofilm-related genes were decreased under the action of the nanocomposites.

Conclusion

An AMP@PDA@AgNPs nanocomposite with good biocompatibility was successfully prepared. The nanocomposite could destruct bacterial biofilms by inhibiting the expression of biofilm-related genes. The synergistic strategy of AMPs and AgNPs could provide a new perspective for the treatment of bacterial infection.

Facile Synthesis of Bio-Antimicrobials with "Smart" Triiodides

Multi-drug resistant pathogens are a rising danger for the future of mankind. Iodine (I₂) is a centuries-old microbicide, but leads to skin discoloration, irritation, and uncontrolled iodine release. Plants rich in phytochemicals have a long history in basic health care. Aloe Vera Barbadensis Miller (AV) and Salvia officinalis L. (Sage) are effectively utilized against different ailments. Previously, we investigated the antimicrobial activities of smart triiodides and iodinated AV hybrids. In this work, we combined iodine with Sage extracts and pure AV gel with polyvinylpyrrolidone (PVP) as an encapsulating and stabilizing agent. Fourier transform infrared spectroscopy (FT-IR), Ultraviolet-visible spectroscopy (UV-Vis), Surface-Enhanced Raman Spectroscopy (SERS), microstructural analysis by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-Ray-Diffraction (XRD) analysis verified the composition of AV-PVP-Sage-I₂. Antimicrobial properties were investigated by disc diffusion method against 10 reference microbial strains in comparison to gentamicin and nystatin. We impregnated surgical sutures with our biohybrid and tested their inhibitory effects. AV-PVP-Sage-I₂ showed excellent to intermediate antimicrobial activity in discs and sutures. The iodine within the polymeric biomaterial AV-PVP-Sage-I₂ and the synergistic action of the two plant extracts enhanced the microbial inhibition. Our compound has potential for use as an antifungal agent, disinfectant and coating material on sutures to prevent surgical site infections.

A critical review on silver nanoparticles: From synthesis and applications to its mitigation through low-cost adsorption by biochar

Silver nanoparticles are one of the most beneficial forms of heavy metals in nanotechnology applications. Due to its exceptional antimicrobial properties, low electrical and thermal resistance, and surface plasmon resonance, silver nanoparticles are used in a wide variety of products, including consumer goods, healthcare, catalysts, electronics, and analytical equipment. As the production and applications of silver nanoparticles containing products increase daily, the environmental pollution due to silver nanoparticles release is increasing and affecting especially the aqueous ecosystem. Silver nanoparticles can kill useful bacteria in soil and water, and bioaccumulate in living organisms even at low concentrations from 10^-2 to 10 μg/mL silver can show antibacterial effect. On the other hand, the maximum silver discharge limit into freshwater is 0.1 μg/L and 3.2 μg/L for Australia and the USA, respectively. To reduce its toxic consequences and meet the regulatory guidelines, it is crucial to remove silver nanoparticles from wastewater before it is discharged into other water streams. Several technologies are available to remove silver nanoparticles, but the adsorption process using low-cost adsorbents is a promising alternative to mitigate silver nanoparticle pollution in the bulk stage. As one of the low-cost adsorbents, biochar produced from the biomass waste could be a suitable adsorbent. This review focuses on collating the latest evidence on silver nanoparticle production, applications, environmental consequences, and cost-effective technological approaches for silver removal from wastewater.

Clinical Application and Efficacy of Silver Drug in Ophthalmology: A Literature Review and New Formulation of EYE Drops with Drug Silver (I) Complex of Metronidazole with Improved Dosage Form

The use of silver preparations in medicine is becoming increasingly popular. The basic aim of this evaluation was to review the literature on the clinical (in vivo) and antibacterial potential of silver preparations in ophthalmic diseases. The second goal was to summarize the results of experimental research on the use of silver preparations in ophthalmology. The third objective was to present a method for stabilizing eye drops containing silver (I) complex. Analysis of the pH stability of the silver (I) complex with metronidazole in the prepared dosage form (eye drops) was carried out. Most silver preparations are clinically used for topical application. Few experimental results indicate the usefulness of intraocular or systemic administration of silver (I) preparations as an alternative or additional therapy in infectious and angiogenic eye diseases. The development of a new formulation increases the stability of the dosage form. New forms of silver (I) products will certainly find application in the treatment of many ophthalmic diseases. One of the most important features of the silver (I) complex is its capacity to break down bacterial resistance. The new eye drops formula can significantly improve comfort of use. Due to their chemical nature, silver (I) compounds are difficult to stabilize, especially in the finished dosage form.

Biomimetic vs. Direct Approach to Deposit Hydroxyapatite on the Surface of Low Melting Point Polymers for Tissue Engineering

Polymers are widely used in many applications in the field of biomedical engineering. Among eclectic selections of polymers, those with low melting temperature (T_m < 200 °C), such as poly(methyl methacrylate), poly(lactic-co-glycolic acid), or polyethylene, are often used in bone, dental, maxillofacial, and corneal tissue engineering as substrates or scaffolds. These polymers, however, are bioinert, have a lack of reactive surface functional groups, and have poor wettability, affecting their ability to promote cellular functions and biointegration with the surrounding tissue. Improving the biointegration can be achieved by depositing hydroxyapatite (HAp) on the polymeric substrates. Conventional thermal spray and vapor phase coating, including the Food and Drug Administration (FDA)-approved plasma spray technique, is not suitable for application on the low T_m polymers due to the high processing temperature, reaching more than 1000 °C. Two non-thermal HAp coating approaches have been described in the literature, namely, the biomimetic deposition and direct nanoparticle immobilization techniques. In the current review, we elaborate on the unique features of each technique, followed by discussing the advantages and disadvantages of each technique to help readers decide on which method is more suitable for their intended applications. Finally, the future perspectives of the non-thermal HAp coating are given in the conclusion.

Multifunctional Coating with Both Thermal Insulation and Antibacterial Properties Applied to Nickel-Titanium Alloy

BACKGROUND

With excellent shape memory and superelastic properties, shape memory alloy (SMA) is an ideal actuator, and it can form smart structure for different applications in medical field. However, SMA devices cause apparent thermal damage to the surrounding tissues when it works in vivo, making the application of smart structure that is composed of SMA actuator in vivo is greatly limited.

METHODS

In this paper, coating (APA) with PLA as the main body to limit the heat conduction, a multifunctional Ag nanoparticles (AgNPs)/polylactic acid (PLA)/Al2O3 was synthesized. The Al2O3 layer was formed by micro-arc oxidation (MAO) and AgNPs were synthesized by silver nitrate and ethylene glycol. Scanning electron microscopy, transmission electron microscope, and Fourier transform infrared spectra were applied to analyze the morphology and characterization of APA coating. The antimicrobial activity, thermal insulation activity, and biocompatibility of APA coating were furtherly explored and verified through animal experiments and immunohistochemistry.

RESULTS

With different particle sizes and concentrations of AgNPs, APA multi-functional films were successfully prepared. The Al2O3 layer was closely combined with SMA and formed a porous surface, so the PLA and AgNPs layers can firmly adhere to SMA, thus reducing the release of nickel ions in SMA. AgNPs gave APA coating excellent antibacterial activity and effectively inhibited the growth of Staphylococcus aureus. In addition, coupled with the low thermal conductivity of PLA and Al2O3, AgNPs were tightly anchored on the surface of PLA, which has high infrared reflectivity, making the APA coating obtain good thermal insulation performance.

CONCLUSION

We have successfully prepared the APA coating and obtained the optimum amount of AgNPs, which makes it have good thermal insulation performance, good antibacterial activity and good biocompatibility, which provides a new prospect for the application of SMA.

Facile Synthesis of Antimicrobial Aloe Vera-"Smart" Triiodide-PVP Biomaterials

Antibiotic resistance is an eminent threat for the survival of mankind. Nosocomial infections caused by multidrug resistant microorganisms are a reason for morbidity and mortality worldwide. Plant-based antimicrobial agents are based on synergistic mechanisms which prevent resistance and have been used for centuries against ailments. We suggest the use of cost-effective, eco-friendly Aloe Vera Barbadensis Miller (AV)-iodine biomaterials as a new generation of antimicrobial agents. In a facile, one-pot synthesis, we encapsulated fresh AV gel with polyvinylpyrrolidone (PVP) as a stabilizing agent and incorporated iodine moieties in the form of iodine (I2) and sodium iodide (NaI) into the polymer matrix. Ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FT-IR), x-ray diffraction (XRD), microstructural analysis by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) verified the composition of AV-PVP-I2, AV-PVP-I2-NaI. AV, AV-PVP, AV-PVP-I2, AV-PVP-I2-NaI, and AV-PVP-NaI were tested in-vitro by disc diffusion assay and dip-coated on polyglycolic acid (PGA) sutures against ten microbial reference strains. All the tested pathogens were more susceptible towards AV-PVP-I2 due to the inclusion of "smart" triiodides with halogen bonding in vitro and on dip-coated sutures. The biocomplexes AV-PVP-I2, AV-PVP-I2-NaI showed remarkable antimicrobial properties. "Smart" biohybrids with triiodide inclusions have excellent antifungal and promising antimicrobial activities, with potential use against surgical site infections (SSI) and as disinfecting agents.

Preparation of a New Biocomposite Designed for Cartilage Grafting with Antibiofilm Activity

New polymer–inorganic composites with antibiofilm features based on the granulated poly(tetrafluoroethylene) (PTFE) and apatite materials were obtained using a standard hydraulic press. The study was performed in hydroxy- and fluorapatites doped with different amounts of silver ions and followed by heat treatment at 600 °C. The structural, morphological, and physicochemical properties were determined by X-ray powder diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy-energy-dispersive spectrometry (SEM-EDS), and transition electron microscopy (TEM). The antibacterial properties of the obtained materials were evaluated against Gram-negative pathogens such as Pseudomonas aeruginosa, Klebsiella pneumoniae, and Escherichia coli as well as against Gram-positive bacteria Staphylococcus epidermidis. The cytotoxicity assessment was carried out on the red blood cells (RBC) as a cell model for in vitro study. Moreover, the biofilm formation on the biocomposite surface was studied using confocal laser scanning microscopy (CLSM).

Destruction of Pseudomonas aeruginosa pre-formed biofilms by cationic polymer micelles bearing silver nanoparticles

Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen often associated with biofilm infections. This study evaluated the capacity for biofilm destruction of a novel combination of cationic polymer micelles formed from poly(2-(dimethylamino)ethyl methacrylate)-b-poly(ε-caprolactone)-b-poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA-PCL-PDMAEMA) triblock copolymer either alone, or loaded with silver nanoparticles (M_AgNPs). Pre-formed P. aeruginosa biofilms were incubated with either blank micelles, AgNO₃, or M_AgNPs. Biofilm biomass (crystal violet assay), metabolic activity (Alamar blue reduction), structure (SEM) and viability (CLSM after Live/Dead staining, or plating for CFU) were checked. The results showed that the micelles alone loosened the biofilm matrix, and caused some alterations in the bacterial surface. AgNO₃ killed the bacteria in situ leaving dead biofilm bacteria on the surface. M_AgNPs combined the two types of activities causing significant biofilm reduction, and alteration and death of biofilm bacteria. Therefore, the applied PDMAEMA-based micelles appear to be a successful candidate for the treatment of P. aeruginosa biofilm infections.

Surface modification of corneal prosthesis with nano-hydroxyapatite to enhance in vivo biointegration

The majority of clinical corneal prostheses (KPros) adopt a core-skirt configuration. This configuration is favored owing to the optic core (generally a cylindrical, acrylic-based material, such as PMMA), that not only provides a clear window for the patients' vision, but also confers resistance to biodegradability. The surrounding skirt (typically a biological material, such as corneal tissue) allows for host tissue integration. However, due to poor biointegration between the dissimilar core and skirt materials, it results in a weak adhesion at the interface, giving rise to clinical complications, such as bacterial infections in the tissue-PMMA interface and device extrusion. Here, we physically immobilized nano-hydroxyapatite (nHAp) on a PMMA cylinder via a dip-coating technique, to create a bioactive surface that improved biointegration in vivo. We established that the nHAp coating was safe and stable in the rabbit cornea over five weeks. More importantly, we found that apoptotic, wound healing and inflammatory responses to nHAp-coated PMMA were substantially milder than to non-coated PMMA. More mature collagen, similar to the non-operated cornea, was maintained in the corneal stroma adjacent to the nHAp-coated implant edge. However, around the non-coated cylinder, an abundant new and loose connective tissue formed, similar to bone tissue response to bioinert scaffolds. As a result of superior biointegration, tissue adhesion with nHAp-coated PMMA cylinders was also significantly enhanced compared to non-coated cylinders. This study set a precedent for the future application of the nHAp coating on clinical KPros. STATEMENT OF SIGNIFICANCE: Currently, all clinical corneal prostheses utilize as-manufactured, non-surface modified PMMA optic cylinder. The bioinert cylinder, however, has poor biointegration and adhesion with the surrounding biological tissue, which can give rise to postoperative complications, such as microbial invasion in the tissue-PMMA loose interface and PMMA optic cylinder extrusion. In the current study, we showed that surface modification of the PMMA cylinder with bioactive nano-hydroxyapatite (nHAp) significantly enhanced its biointegration with corneal stromal tissue in vivo. The superior biointegration of the nHAp-coated PMMA was signified by a more attenuated corneal wound healing, inflammatory and fibrotic response, and better tissue apposition, as well as a significantly improved corneal stromal tissue adhesion when compared to the non-coated PMMA.

"Smart" Antimicrobial Nanocomplexes with Potential to Decrease Surgical Site Infections (SSI)

The emergence of resistant pathogens is a burden on mankind and threatens the existence of our species. Natural and plant-derived antimicrobial agents need to be developed in the race against antibiotic resistance. Nanotechnology is a promising approach with a variety of products. Biosynthesized silver nanoparticles (AgNP) have good antimicrobial activity. We prepared AgNPs with trans-cinnamic acid (TCA) and povidone-iodine (PI) with increased antimicrobial activity. We synthesized also AgNPs with natural cinnamon bark extract (Cinn) in combination with PI and coated biodegradable Polyglycolic Acid (PGA) sutures with the new materials separately. These compounds (TCA-AgNP, TCA-AgNP-PI, Cinn-AgNP, and Cinn-AgNP-PI) and their dip-coated PGA sutures were tested against 10 reference strains of microorganisms and five antibiotics by zone inhibition with disc- and agar-well-diffusion methods. The new compounds TCA-AgNP-PI and Cinn-AgNP-PI are broad spectrum microbicidal agents and therefore potential coating materials for sutures to prevent Surgical Site Infections (SSI). TCA-AgNP-PI inhibits the studied pathogens stronger than Cinn-AgNP-PI in-vitro and on coated sutures. Dynamic light scattering (DLS), ultraviolet-visible spectroscopy (UV-Vis), Fourier Transform infrared spectroscopy (FT-IR), Raman, x-ray diffraction (XRD), microstructural analysis by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) confirmed the composition of TCA-AgNP-PI and Cinn-AgNP-PI. Smart solutions involving hybrid materials based on synergistic antimicrobial action have promising future perspectives to combat resistant microorganisms.