Recent Advances in Silver Nanoparticles Containing Nanofibers for Chronic Wound Management

Optimizing processes and unveiling the therapeutic potential of electrospun gelatin nanofibers for biomedical applications

Gelatin, derived primarily from animal sources such as bovine, porcine, and fish skin and bones, exhibits remarkable properties that make it an ideal candidate for various contemporary applications. Its unique attributes include excellent biocompatibility, non-toxicity, biodegradability, low immunogenicity, ease of chemical modification, and structural similarity to the extracellular matrix (ECM). These features have led to the development of gelatin-based biomaterials with tunable properties and specialized functionalities. Electrospinning remains the most widely adopted and effective technique for fabricating gelatin nanofibers. These nanofibers are gaining significant attention in the biomedical sector due to their adjustable fiber morphology, enhanced surface properties, controllable porosity, mechanical adaptability, high surface area, multi-scale pore size distribution, and intrinsic bioactive characteristics. Functionalized gelatin-based electrospun nanofibers are a rapidly advancing area in the life sciences, enabling the creation of innovative drug delivery platforms and next-generation scaffolds for tissue regeneration. Their applications span across various domains, including bone and cartilage repair, retinal and vascular engineering, myocardial regeneration, cancer therapy, chronic wound management, and biosensor development. In this article, we provide a comprehensive assessment of the progression of gelatin-based nanofibers, highlight the critical parameters governing the electrospinning of gelatin, and explore recent innovations in diverse biomedical fields, emphasizing significant advancements and research findings.

Therapeutic Potential of AgNP-Infused Patches in Periodontal Disease: An Observational Study in Albino Rats

Introduction

Silver nanoparticles (AgNPs) have emerged as a promising therapeutic modality in periodontal disease management due to their potent antimicrobial activity and ability to promote tissue regeneration. This study aimed to evaluate the efficacy of AgNP-infused patches in ligature-induced periodontitis rat model.

Methods

AgNPs were synthesized using a green synthesis method with neem (Azadirachta indica) leaf extract followed by incorporation into polyvinyl alcohol (PVA)-based patches. In vivo efficacy of experimental AgNP patch was tested in albino rats vs marketed formulation and control groups, following ARRIVE guidelines.

Results

Characterization by Atomic Force Microscopy revealed spherical AgNPs with an average size of 85 nm, while Field Emission Scanning Electron Microscopy confirmed uniform morphology and size distribution. Production of microporous AgNP patches with uniform nanoparticle dispersion was also validated by Scanning electron microscopy and Energy Dispersive X-ray Analysis. Observational and histopathological analysis revealed significant improvements in gingival and periodontal tissue restoration, inflammation reduction in the AgNP-treated groups compared to untreated and standard-treated groups.

Discussion

Notably, the high-dose AgNP patch (1000 mg/kg) treated group exhibited near-complete tissue restoration. These findings highlight the potential of AgNP patch as a localized treatment alternative for periodontal disease.

A review on plant-mediated synthesis of AgNPs and their formulations for wound healing application

Wound healing is a sophisticated and dynamic process carried out by a myriad of cellular activities that work together in a coordinated manner to effectively repair damaged tissue. It involves a cascade process involving hemostasis, inflammation, granulation, maturation, and remodeling. However, in the case of chronic wounds, owing to the delayed wound healing process, various microbes invade the wound area and produce biofilms that hinder the healing process. Owing to rapid advancements in nanotechnology, several nanomaterials with diverse formulations have been investigated for wound healing. Among them, silver nanoparticles (AgNPs) have shown excellent properties, as they have unique physiochemical properties that address the problems associated with wound healing. The antibacterial and antioxidant properties of silver greatly enhance wound-care diagnostics. The use of medicinal plants for green synthesis of AgNPs has been widely researched, with these plants serving as both reducing and stabilizing agents in the nanoparticle formation process. This review focuses on different wound types, problems related to wounds, green-synthesized AgNPs using medicinal plants, and their limitations and advantages in wound dressing formulations. This study aims to provide the scientific community with a directional view in analyzing the role and importance of green-synthesized AgNPs in wound care.

An Innovative Approach Based on the Green Synthesis of Silver Nanoparticles Using Pomegranate Peel Extract for Antibacterial Purposes

This study describes a green synthesis method for silver nanoparticles (AgNPs) using autochthonous "Mollar de Elche" pomegranate peel extract and optimized through a Python-programmed Box-Behnken design (BBD) created specifically for the work. The bioactive compounds in pomegranate, particularly punicalagin, serve as effective reducing and stabilizing agents. BBD was used to analyze the effects of dependent variables such as silver nitrate concentration, pomegranate extract concentration, and temperature on responses such as hydrodynamic diameter, polydispersity index, and zeta potential, minimizing experimental trials and highlighting variable interactions. Optimal conditions were experimentally validated and agreed well with the predicted values. The optimized AgNPs were characterized via ultraviolet-visible spectrophotometry, Fourier transform infrared spectroscopy, X-ray diffraction, and field emission scanning electron microscopy. These AgNPs demonstrated substantial antibacterial activity against Escherichia coli and Staphylococcus aureus. Furthermore, the AgNPs were incorporated into nanofibrous scaffolds as a proof of concept for potential biomedical applications, where their antibacterial activity was partially retained postincorporation. This study highlights the potential of pomegranate extract as a sustainable medium for AgNP synthesis with promising antibacterial applications and the ability of the BBD as a useful tool for efficient optimization of multivariable processes, including the synthesis of nanomaterials.

Application of phytosynthesized silver nanoparticles (SNPs) against Erwinia amylovora causing fire blight disease

The bacterium Erwinia amylovora is responsible for the destructive disease known as fire blight in pear trees. This highly detrimental condition poses a significant threat to the health and vitality of these trees. The existing strategies for managing fire blight disease involve the regular use of copper compounds and streptomycin, particularly during periods when environmental factors are conducive to the spread of the infection. Silver nanoparticles, also known as SNPs, are tiny specks of silver ranging in size from 10 to 100 nm. These particles are created through various chemical and biological processes. Numerous studies have demonstrated their ability to exhibit antibacterial properties against a wide range of human and animal pathogens. In this investigation, the dimensions of SNPs were ascertained by employing aqueous extracts derived from apple, pear, and quince leaves. The average sizes of the SNPs were found to be approximately 30 nm, 38 nm, and 55 nm, apple, quince and pear respectively. The pear mature fruits successfully managed to control the rot caused by the disease-causing E. amylovora. This study shows the viability of utilizing leaves extract from apple, pear, and quince as a suitable medium for the production of silver nanoparticles. These nanoparticles hold potential for effectively managing fire blight disease.

Clinical Presentation and Integrated Management of Pressure Injuries in the Emergency Hospital Setting: A Plastic Surgeon's Perspective

Background: Pressure injuries are localized areas of tissue damage or necrosis that occur when pressure is applied to the skin for prolonged periods, often over bony prominences, often the sacrum, heels, ischial tuberosities, and greater trochanters. The pathophysiology is complex, involving a combination of mechanical forces, ischemia, and tissue hypoxia. Methods: We conducted a 2-year retrospective study aiming to assess the clinical characteristics, risk factors, and management of pressure injuries in patients admitted to an emergency hospital who underwent a plastic surgery examination. Results: This study included 176 patients with clinically diagnosed pressure ulcers, with findings showing 28.52% of cases as stage III and 35.57% as stage IV. Common sites included the sacrum (40.94%), ischium (15.1%), and heel (14.43%). The median patient age was 76 years, with 47.15% between 60 and 80 years and 36.93% ≥ 80 years, often presenting with comorbidities increasing the risk of pressure injuries, such as cardiovascular disease (71.59%), diabetes (18.18%) and obesity (9.66%). Important risk factors included neurological diseases (46.02%), spinal cord injuries (14.7%), and nutritional deficiencies, as indicated by anemia (10.43g/dL; 95% CI [10.04; 10.82]), low serum albumin (2.56 g/dL; 95% CI [2.43; 2.69]) and proteins (5.54 g/dL; 95% CI [5.34; 5.73]). Mortality was significant, at 36.93%, with 23.3% occurring within the first 7 days of hospitalization due to the patients' critical condition. Decision-making for surgical intervention considered the patient's general status, comorbidities, and ulcer severity. Surgical treatment consisted of seriate debridement, negative pressure vacuum therapy, and/or coverage using skin grafting, local advancement, or rotation flaps. Conclusions: The key question for a plastic surgeon to consider is how pressure ulcers should be managed. Various debridement and covering techniques should be tailored to the wound's characteristics, considering patient comorbidities and general health condition.

Transparent and Mechanically Robust Janus Nanofiber Membranes for Open Wound Healing and Monitoring

The electrospun nanofiber membrane has demonstrated great potential for wound management due to its porous structure, large surface area, mechanical strength, and barrier properties. However, there is a need to develop transparent bioactive nanofibers with strong mechanical properties to facilitate the monitoring of the healing process. In this study, we present an electrospinning-based method for creating transparent (∼80-90%), strong (∼11-13 MPa), and Janus nanofiber membranes. The innovative square pattern architecture of the membrane includes a thin hydrophobic polycaprolactone layer on top of a layer of hydrophilic ethylene-vinyl alcohol nanofiber, which enables the absorption of excess biofluid from the wound and exhibits Janus wettability for water. Furthermore, incorporating 5% chitosan into the composition of the nanofibers accelerates the healing process through its antioxidant properties and antimicrobial activity against various bacteria, including drug-resistant strains. The developed membrane also demonstrates skin-repairing function, quick blood clotting (around 145 ± 12 s), and biocompatibility with keratinocyte (≥90%), as well as in vitro quick cell migration (∼24 h). With a tensile strength of 11-13 MPa, the membrane effectively adheres to the knee joint even after running 4 km. These optimal properties of the electrospun nanofiber membrane make it suitable for effective wound management and inspection of the healing process, without the need for frequent dressing changes.

Silk Fibroin Nanofibers: Advancements in Bioactive Dressings through Electrospinning Technology for Diabetic Wound Healing

BACKGROUND

Non-healing diabetic wounds represent a significant clinical challenge globally, necessitating innovative approaches in drug delivery to enhance wound healing. Understanding the pathogenesis of these wounds is crucial for developing effective treatments. Bioactive dressings and polymeric nanofibers have emerged as promising modalities, with silk biomaterials gaining attention for their unique properties in diabetic wound healing.

PURPOSE OF REVIEW

The purpose of this review is to examine the challenges and innovations in treating non-healing diabetic wounds, emphasizing the global burden and the need for effective solutions. This review explores the complex mechanisms of wound healing in diabetes and evaluates the therapeutic potential of bioactive dressings and polymeric nanofibers. Special focus is given to the application of silk biomaterials, particularly silk fibroin, for wound healing, detailing their properties, mechanisms, and clinical translation. This review also describes various nanofiber fabrication methods, especially electrospinning technology, and presents existing evidence on the effectiveness of electrospun silk fibroin formulations.

RECENT FINDINGS

Recent advancements highlight the potential of silk biomaterials in diabetic wound healing, owing to their biocompatibility, mechanical strength, and controlled drug release properties. Electrospun silk fibroin-based formulations have shown promising results in preclinical and clinical studies, demonstrating accelerated wound closure and tissue regeneration.

SUMMARY

Non-healing diabetic wounds present a significant healthcare burden globally, necessitating innovative therapeutic strategies. Bioactive dressings and polymeric nanofibers, particularly silk-based formulations fabricated through electrospinning, offer promising avenues for enhancing diabetic wound healing. Further research is warranted to optimize formulation parameters and validate efficacy in larger clinical trials.

Bacteria-Derived Cellulose Membranes Modified with Graphene Oxide-Silver Nanoparticles for Accelerating Wound Healing

This study reports on the modification of bacterial cellulose (BC) membranes produced by static fermentation of Komagataeibacter xylinus bacterial strains with graphene oxide-silver nanoparticles (GO-Ag) to yield skin wound dressings with improved antibacterial properties. The GO-Ag sheets were synthesized through chemical reduction with sodium citrate and were utilized to functionalize the BC membranes (BC/GO-Ag). The BC/GO-Ag composites were characterized to determine their surface charge, morphology, exudate absorption, antimicrobial activity, and cytotoxicity by using fibroblast cells. The antimicrobial activity of the wound dressings was assessed against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. The results indicate that the BC/GO-Ag dressings can inhibit ∼70% of E. coli cells. Our findings also revealed that the porous BC/GO-Ag antimicrobial dressings can efficiently retain 94% of exudate absorption after exposure to simulated body fluid (SBF) for 24 h. These results suggest that the dressings could absorb excess exudate from the wound during clinical application, maintaining adequate moisture, and promoting the proliferation of epithelial cells. The BC/GO-Ag hybrid materials exhibited excellent mechanical flexibility and low cytotoxicity to fibroblast cells, making excellent wound dressings able to control bacterial infectious processes and promote the fast healing of dermal lesions.

Nanomaterial strategies in wound healing: A comprehensive review of nanoparticles, nanofibres and nanosheets

Wound healing is a complex process that orchestrates the coordinated action of various cells, cytokines and growth factors. Nanotechnology offers exciting new possibilities for enhancing the healing process by providing novel materials and approaches to deliver bioactive molecules to the wound site. This article elucidates recent advancements in utilizing nanoparticles, nanofibres and nanosheets for wound healing. It comprehensively discusses the advantages and limitations of each of these materials, as well as their potential applications in various types of wounds. Each of these materials, despite sharing common properties, can exhibit distinct practical characteristics that render them particularly valuable for healing various types of wounds. In this review, our primary focus is to provide a comprehensive overview of the current state-of-the-art in applying nanoparticles, nanofibres, nanosheets and their combinations to wound healing, serving as a valuable resource to guide researchers in their appropriate utilization of these nanomaterials in wound-healing research. Further studies are necessary to gain insight into the application of this type of nanomaterials in clinical settings.

Fabrication and evaluation of a bi-layered electrospun PCL/PVA patch for wound healing: Release of vitamins and silver nanoparticle

There is still little research on the co-delivery of vitamins and AgNPs to accelerate wound healing. In this study, a bi-layered electrospun PCL/PVA patch loaded with Vitamin C, Vitamin B12, and AgNPs was fabricated using a co-spinning technique. SEM, FTIR, degradation, swelling, tensile strength, disk diffusion, and MTT assay were studied. Nine rats were placed in three groups (control: no treatment, G1: without agents, and G2: with agents) for 14 days in an in-vivo study. H&E and Masson Trichrome staining were employed for histological analysis. Results showed that the final electrospun wound dressings depicted nanofibers with diameters ranging from 100 to 500 nm. The presence of AgNP enhanced the mechanical strength (40-50 MPs). An appropriate swelling (100 %) and degradation (50 %) rate was observed for groups with no significant difference (P > 0.05). G1 and G2 did not show a significant difference in terms of porosity (65 % vs. 69 %). Regarding WVTR, G2 demonstrated higher WVTR (88 vs. 95 g/m2. h). G2 showed a vitamin release of more than 90 % after 48 h. Compared to G1, G2 demonstrated good antibacterial activity (>3 cm) against E. Coli and S. aureous (P < 0.01), with cell viability of more than 93 % (P > 0.05). Furthermore, the in-vivo study approved that G2 accelerated wound healing in full-thickness wounds, compared to the control groups, with notable wound size reduction (8 mm), epithelialization, and collagen formation. The findings support the use of this simple but potent electrospun wound dressing for the healing of full-thickness wounds.

Receptor Targeting Using Copolymer-Modified Gold Nanoparticles for pCMV-Luc Gene Delivery to Liver Cancer Cells In Vitro

The formulation of novel delivery protocols for the targeted delivery of genes into hepatocytes by receptor mediation is important for the treatment of liver-specific disorders, including cancer. Non-viral delivery methods have been extensively studied for gene therapy. Gold nanoparticles (AuNPs) have gained attention in nanomedicine due to their biocompatibility. In this study, AuNPs were synthesized and coated with polymers: chitosan (CS), and polyethylene glycol (PEG). The targeting moiety, lactobionic acid (LA), was added for hepatocyte-specific delivery. Physicochemical characterization revealed that all nano-formulations were spherical and monodispersed, with hydrodynamic sizes between 70 and 250 nm. Nanocomplexes with pCMV-Luc DNA (pDNA) confirmed that the NPs could bind, compact, and protect the pDNA from nuclease degradation. Cytotoxicity studies revealed that the AuNPs were well tolerated (cell viabilities > 70%) in human hepatocellular carcinoma (HepG2), embryonic kidney (HEK293), and colorectal adenocarcinoma (Caco-2) cells, with enhanced transgene activity in all cells. The inclusion of LA in the NP formulation was notable in the HepG2 cells, which overexpress the asialoglycoprotein receptor on their cell surface. A five-fold increase in luciferase gene expression was evident for the LA-targeted AuNPs compared to the non-targeted AuNPs. These AuNPs have shown potential as safe and suitable targeted delivery vehicles for liver-directed gene therapy.

Effect of Adding Different Concentrations of Silver Nanoparticles on Flexural Strength and Microhardness of Different Denture Base Materials

AIM

This study aimed to evaluate the effect of adding different concentrations of silver nanoparticles (AgNPs) on the flexural strength and microhardness of various denture base materials.

MATERIALS AND METHODS

For this study, a total of 60 specimens were used and divided into equal groups. The first group consisted of heat-cured acrylic resin (Vertex-Germany), while the second group consisted of thermoplastic resin (Breflex 2nd edition, Germany). The samples were created using a split brass mold with dimensions of 65 × 10 × 2.5 mm, in accordance with the specifications of the American Dental Association (specifically No. 12 for flexural and microhardness). Following this, the samples were divided into three groups (A, B, and C) based on different concentrations of AgNPs (0, 2, and 5%). The flexural and microhardness of the samples were assessed using a universal testing machine and the Vickers hardness test, respectively. The data were gathered, organized, and analyzed using statistical methods.

RESULTS

The flexural strength findings showed a significant difference between the two groups. Also, there was a considerable decrease in the average value of the acrylic group as the concentrations of AgNPs rose, while the flexural strength of the thermoplastic group notably improved. Regarding microhardness, the results showed a significant difference between the two groups. It showed that the mean value of both groups increased with increasing concentrations of AgNPs.

CONCLUSION

Within the limitations of laboratory testing conditions of this study, it was discovered that AgNPs negatively impact the flexural strength of acrylic resins. Furthermore, an increase in the concentration of AgNPs was found to be directly related to the flexural strength of thermoplastic resin and the microhardness of both groups.

CLINICAL SIGNIFICANCE

The concentration of AgNPs has a significant impact on certain mechanical properties of denture base materials, but it is important to consider their potential toxicity. How to cite this article: El-Hussein IG. Effect of Adding Different Concentrations of Silver Nanoparticles on Flexural Strength and Microhardness of Different Denture Base Materials. J Contemp Dent Pract 2024;25(5):417-423.

Nanomaterials in the Wound Healing Process: New Insights and Advancements

Wounds, which are becoming more common as a result of traumas, surgery, burns, and chronic illnesses like diabetes, remain a critical medical problem. Infectious bacteria impact the healing process, particularly if its biofilm (biological films) leads to a prolonged effect. Nanomaterials have emerged as promising candidates in the field of wound healing due to their unique properties and versatile applications. New insights into the interactions between nanomaterials and wound microenvironments have shed light on the mechanisms underlying their therapeutic effects. However, a significantly minimal amount of research has been carried out to see if these nanomaterials significantly promote the wound healing process. In this review, we provided an outline of the various types of nanomaterials that have been studied for healing wounds and infection prevention. Overall, the utilization of nanomaterials in wound healing holds great promise and continues to evolve, providing new opportunities for the development of effective and efficient wound care therapies.

Exploring an Innovative Approach: Integrating Negative-Pressure Wound Therapy with Silver Nanoparticle Dressings in Skin Graft Procedures

BACKGROUND

Skin grafting is a helpful instrument in a plastic surgeon's arsenal. Several types of dressings were designed to facilitate the process of graft integration. Negative-pressure wound therapy is a proven dressing method, enhancing graft survival through several mechanisms: aspiration of secretions, stimulation of neoangiogenesis, and promotion of an anti-inflammatory environment. Silver nanoparticle dressings also bring multiple benefits by bearing an antimicrobial effect and providing a humid medium, which are favorable for epithelialization. The combination of NPWT (negative-pressure wound therapy) with AgNPs (silver nanoparticles) has not been widely studied.

MATERIALS AND METHODS

This study aimed to compare the outcomes of silver nanoparticle sheets with the combination of negative-pressure wound therapy and silver nanoparticle dressings. We conducted a comparative prospective study on 80 patients admitted to the Plastic Surgery Department of "Prof. Dr. Agrippa Ionescu" Emergency Clinical Hospital between 1st of January 2020 and 31st of December 2022. The study population was randomized to receive either silver nanoparticle dressings or negative-pressure wound therapy (NPWT) combined with silver nanoparticle dressings. Various parameters were monitored, including patient comorbidities and graft-related data such as defect etiology, graft integration, and graft size. Dressings were changed, and graft status was evaluated at 7, 10, and 14 days postoperatively. Additionally, baseline C-reactive protein (CRP) levels were measured before surgery and 7, 10, and 14 days postoperatively.

RESULTS

The study demonstrated an enhanced integration of skin grafts at all evaluation stages when employing NPWT combined with AgNPs, particularly evident 10 days post operation. Significant variations in graft integration were also observed based on factors such as diabetes, cardiovascular disease, graft size, or the origin of the grafted defect. Moreover, dynamic C-reactive protein monitoring showed a statistically significant decrease in CRP levels 10 days post operation among patients treated with NPWT in conjunction with silver dressing, consistent with the nearly complete integration of skin grafts at this evaluation threshold.

CONCLUSION

Several factors influence the postoperative evolution of split-skin grafts. Postoperative dressings target local factors to enhance graft integration further. Our research demonstrated that the innovative combination of NPWT-assisted dressings, complemented by a silver nanoparticle sheet, resulted in improved benefits for graft integration and the alleviation of systemic inflammation.

Silver Nanoparticles In Situ Synthesized and Incorporated in Uniaxial and Core-Shell Electrospun Nanofibers to Inhibit Coronavirus

In the present study, we sought to develop materials applicable to personal and collective protection equipment to mitigate SARS-CoV-2. For this purpose, AgNPs were synthesized and stabilized into electrospinning nanofiber matrices (NMs) consisting of poly(vinyl alcohol) (PVA), chitosan (CHT), and poly-ε-caprolactone (PCL). Uniaxial nanofibers of PVA and PVA/CHT were developed, as well as coaxial nanofibers of PCL[PVA/CHT], in which the PCL works as a shell and the blend as a core. A crucial aspect of the present study is the in situ synthesis of AgNPs using PVA as a reducing and stabilizing agent. This process presents few steps, no additional toxic reducing agents, and avoids the postloading of drugs or the posttreatment of NM use. In general, the in situ synthesized AgNPs had an average size of 11.6 nm, and the incorporated nanofibers had a diameter in the range of 300 nm, with high uniformity and low polydispersity. The NM's spectroscopic, thermal, and mechanical properties were appropriate for the intended application. Uniaxial (PVA/AgNPs and PVA/CHT/AgNPs) and coaxial (PCL[PVA/CHT/AgNPs]) NMs presented virucidal activity (log's reduction ≥ 5) against mouse hepatitis virus (MHV-3) genus Betacoronavirus strains. In addition to that, the NMs did not present cytotoxicity against fibroblast cells (L929 ATCC® CCL-1TM lineage).

Nanosilver-Functionalized Hybrid Hydrogels of Carboxymethyl Cellulose/Poly(Vinyl Alcohol) with Antibacterial Activity for Prevention and Therapy of Infections of Diabetic Chronic Wounds

Diabetic foot ulcers (DFUs) are considered one of the most severe chronic complications of diabetes and can lead to amputation in severe cases. In addition, bacterial infections in diabetic chronic wounds aggravate this scenario by threatening human health. Wound dressings made of polymer matrices with embedded metal nanoparticles can inhibit microorganism growth and promote wound healing, although the current clinical treatments for diabetic chronic wounds remain unsatisfactory. In this view, this research reports the synthesis and characterization of innovative hybrid hydrogels made of carboxymethyl cellulose (CMC) and poly(vinyl alcohol) (PVA) chemically crosslinked by citric acid (CA) functionalized with silver nanoparticles (AgNPs) generated in situ using an eco-friendly aqueous process. The results assessed through comprehensive in vitro and in vivo assays demonstrated that these hybrid polymer hydrogels functionalized with AgNPs possess physicochemical properties, cytocompatibility, hemocompatibility, bioadhesion, antibacterial activity, and biocompatibility suitable for wound dressings to support chronic wound healing process as well as preventing and treating bacterial infections. Hence, it can be envisioned that, with further research and development, these polymer-based hybrid nanoplatforms hold great potential as an important tool for creating a new generation of smart dressings for treating chronic diabetic wounds and opportunistic bacterial infections.

Antimicrobial and anti-biofilm activities of bio-inspired nanomaterials for wound healing applications

Chronic wounds are ubiquitously inhabited by bacteria, and they remain a challenge as they cause significant discomfort and because their treatment consumes huge clinical resources. To reduce the burden that chronic wounds place upon both patients and health services, a wide variety of approaches have been devised and investigated. Bioinspired nanomaterials have shown great success in wound healing when compared to existing approaches, showing better ability to mimic natural extracellular matrix (ECM) components and thus to promote cell adhesion, proliferation, and differentiation. Wound dressings that are based on bioinspired nanomaterials can be engineered to promote anti-inflammatory mechanisms and to inhibit the formation of microbial biofilms. We consider the extensive potential of bioinspired nanomaterials in wound healing, revealing a scope beyond that covered previously.

Planophila laetevirens-Mediated Synthesis of Silver Nanoparticles: Optimization, Characterization, and Anticancer and Antibacterial Potentials

Algal-mediated synthesis of nanoparticles (NPs) opens the horizon for green and sustainable synthesis of NPs that can be used in many fields, such as medicine and industry. We extracellularly synthesized silver NPs (Ag-NPs) using the novel microalgae Planophila laetevirens under optimized conditions. The isolate was collected from freshwater/soil, purified, morphologically identified, and genetically identified using light, inverted light, scanning electron microscopy, and 18S rRNA sequencing. The phytochemicals in the algal extract were detected by GC-MS. Aqueous biomass extracts and cell-free media were used to reduce silver nitrate to Ag-NPs. To get small, uniformly shaped, and stable Ag-NPs, various abiotic parameters, including precursor concentration, the ratio between the reductant and precursor, temperature, time of temperature exposure, pH, illumination, and incubation time, were controlled during the synthesis of Ag-NPs. B-P@Ag-NPs and S-P@Ag-NPs (Ag-NPs synthesized using biomass and cell-free medium, respectively) were characterized using UV-vis spectroscopy, transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray analysis (EDX) and mapping, Fourier transform infrared (FTIR) spectroscopy, and a zeta sizer. S-P@Ag-NPs had a smaller size (10.8 ± 0.3 nm) than B-P@Ag-NPs (19.0 ± 0.6 nm), while their shapes were uniform quasispherical (S-P@Ag-NPs) and spherical to oval (B-P@Ag-NPs). EDX and mapping analyses demonstrated that Ag was the dominant element in the B-P@Ag-NP and S-P@Ag-NP samples, while FTIR revealed the presence of O-H, C-H, N-H, and C-O groups, indicating that polysaccharides and proteins acted as reductants, while polysaccharides/fatty acids acted as stabilizers during the synthesis of NPs. The hydrodynamic diameters of B-P@Ag-NPs and S-P@Ag-NPs were 37.7 and 28.3 nm, respectively, with negative charges on their surfaces, suggesting their colloidal stability. Anticancer activities against colon cancer (Sw620 and HT-29 cells), breast cancer (MDA-MB231 and MCF-7 cells), and normal human fibroblasts (HFs) were screened using the MTT assay. B-P@Ag-NPs and S-P@Ag-NPs had a greater antiproliferative effect against colon cancer than against breast cancer, with biocompatibility against HFs. The biocidal effects of the B-P@Ag-NPs and S-P@Ag-NPs were evaluated against Escherichia coli, Bacillus cereus, and Bacillus subtilis using agar well diffusion and resazurin dye assays. B-P@Ag-NPs and S-P@Ag-NPs caused higher growth inhibition of Gram-negative bacteria than of Gram-positive bacteria. B-P@Ag-NPs and S-P@Ag-NPs synthesized by P. laetevirens are promising antitumor and biocidal agents.

Wound Coating Collagen-Based Composites with Ag Nanoparticles: Synthesis, Structure and Biological Activity

The search for materials for a new generation of wound coatings is important due to the increase in antibiotic-resistant microorganisms and the number of patients with untreatable chronic purulent wounds. Metal nanoparticles, specifically silver nanoparticles, have antimicrobial activity and do not induce known bacterial resistance. To obtain new Ag-containing nanocomposites, type I collagen was extracted by an enzyme–acid method from cattle tendons. Silver nanoparticles were obtained by an environmentally safe method, metal-vapor synthesis (MVS), which enables obtaining metal nanoparticles without impurities. For this, metal vapors were cocondensed in a vacuum of 10−2 Pa on the walls of a quartz reactor cooled to 77 K using acetone as an organic dispersion medium. The composition of the collagen surface was determined by XPS using the spectra of C1s, N1s, and O1s. The presence of a peak with a binding energy of approximately 368.57 eV in the Ag 3d5/2 spectrum indicates the state of Ag0 silver atoms in the nanocomposite. SEM images showed that collagen contributes to the effective stabilization of Ag nanoparticles with an average size of 13.0 ± 3.5 nm. It was found that collagen is non-toxic and biocompatible with skin cells and fibroblasts. The collagen–Ag nanoparticle nanocomposites exhibited antimicrobial activity against bacteria Bacillus subtilis, Escherichia coli, and fungi Aspergillus niger.

Wound Gel with Antimicrobial Effects Based on Polyvinyl Alcohol and Functional Aryloxycyclotriphosphazene

A silver-containing gel based on polyvinyl alcohol and aryloxycyclotriphosphazene containing β-carboxyethenylphenoxy and p-formylphenoxy groups has been developed. Phosphazene was synthesized via the Doebner reaction from hexakis[(4-formyl)phenoxy]cyclotriphosphazene and malonic acid and characterized by ¹H, ¹³C, and ³¹P NMR spectroscopy and MALDI-TOF mass spectrometry. The study of the gel using scanning electron microscopy showed that the gel contains open pores and can absorb wound exudate. The maximum water absorption capacity of the gel was 272%, which was reached after 80 min of testing. The antimicrobial activity of the obtained silver-containing gel was evaluated using the diffusion method. The gel was found to inhibit the growth of the main microorganisms in contact with the skin: the bacteria S. aureus, P. aeruginosa, E. coli, B. subtilis, S. epidermidis, and C. stationis and the fungus C. albicans. The study of the wound-healing effect of the gel in vivo showed a decrease in the wound area of the rabbit hind limb by 91.43% (p < 0.05) on the 10th day of observation and a decrease in the content of C-reactive protein in the rabbit blood serum by 1.3 times (p < 0.05).

Nanofibrous Scaffolds for Diabetic Wound Healing

Chronic wounds are one of the secondary health complications that develop in individuals who have poorly managed diabetes mellitus. This is often associated with delays in the wound healing process, resulting from long-term uncontrolled blood glucose levels. As such, an appropriate therapeutic approach would be maintaining blood glucose concentration within normal ranges, but this can be quite challenging to achieve. Consequently, diabetic ulcers usually require special medical care to prevent complications such as sepsis, amputation, and deformities, which often develop in these patients. Although several conventional wound dressings, such as hydrogels, gauze, films, and foams, are employed in the treatment of such chronic wounds, nanofibrous scaffolds have gained the attention of researchers because of their flexibility, ability to load a variety of bioactive compounds as single entities or combinations, and large surface area to volume ratio, which provides a biomimetic environment for cell proliferation relative to conventional dressings. Here, we present the current trends on the versatility of nanofibrous scaffolds as novel platforms for the incorporation of bioactive agents suitable for the enhancement of diabetic wound healing.

Nano-Hybrid Ag@LCCs Systems with Potential Wound-Healing Properties

The synthesis of contaminant-free silver@linear carbon chains (Ag@LCCs) nanohybrid systems, at different Ag/LCCs ratios, by pulsed laser ablation was studied. The ablation products were first characterized by several diagnostic techniques: conventional UV-Vis optical absorption and micro-Raman spectroscopies, as well as scanning electron microscopy, operating in transmission mode. The experimental evidence was confirmed by the theoretical simulations' data. Furthermore, to gain a deeper insight into the factors influencing metal@LCCs biological responses in relation to their physical properties, in this work, we investigated the bioproperties of the Ag@LCCs nanosystems towards a wound-healing activity. We found that Ag@LCC nanohybrids maintain good antibacterial properties and possess a better capability, in comparison with Ag NPs, of interacting with mammalian cells, allowing us to hypothesize that mainly the Ag@LCCs 3:1 might be suitable for topical application in wound healing, independent of (or in addition to) the antibacterial effect.