Bio-Based Polymers with Antimicrobial Properties towards Sustainable Development

Synthesis of N-acetylcysteine functionalized cholic acid based triarmed poly DL-Lactide and encapsulation of gold nanoparticles: Studies on the antimicrobial activity and biocompatibility for drug delivery applications

Cholic acid based biodegradable reverse polymeric micelles have been widely utilized as preclinically suitable drug delivery system for poorly water-soluble drugs. In this report, we developed N-acetylcysteine functionalized cholic acid based triarmed poly (Dl-lactide) (ACyCA-triarmed (DLL)n as reversed polymeric micelles for drug delivery studies. ACyCA was synthesized via thiol-yne click reaction and subsequently used as an initiator for the synthesis of ACyCA-triarmed (DLL)n through ring opening polymerization (ROP) using Sn (Oct)2 as a catalyst. The synthesized ACyCA-triarmed (DLL)n was characterized using GPC, FT-IR, 1H NMR, 13C NMR, spectrofluorometer, HR-TEM, DSC, TGA, XRD, DLS, and zeta potential techniques. The reverse critical micellar concentration of the polymer was determined to be 1.99 mg/mL using a spectrofluorometer. The synthesized reverse micelles (RMs) were utilized as a reducing and capping agent for the preparation of AuNPs under sunlight exposure. The formed AuNPs exhibited spherical in shape with an average size of ∼ 23.4 nm and Dh was found to be 86.8 ± 1.3 nm as evidenced by the TEM and DLS analysis. Furthermore, the antimicrobial activity, hemolytic activity, anti-oxidant activity, and in-vitro drug release studies were examined for the RMs-AuNPs and compared with RMs. The hydrophobic nature of RMs and RMs-AuNPs had better haemocompatibility at above the reversed CMC. The antioxidant activity RMs-AuNPs showed better inhibitory effect in a dose-dependent manner as compared to RMs. The RMs-AuNPs formulation act as reservoir for solubilization of hydrophobic doxorubicin (Dox.HCl) drugs and can be used as therapeutic platform for slow and sustained release of drugs in biological medium.

Capparis sepiaria-Loaded Sodium Alginate Single- and Double-Layer Membrane Composites for Wound Healing

Background: Effective wound dressing is the key solution to combating the increased death rate and prolonged hospital stay common to patients with wounds. Methods: Sodium alginate-based single- and double-layer membranes incorporated with Capparis sepiaria root extract were designed using the solvent-casting method from a combination of polyvinyl alcohol (PVA), Pluronic F127 (PF127), and gum acacia. Results: The successful preparation of the membranes and loading of the extract were confirmed using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The prepared membranes were biodegradable and non-toxic to human skin cells (HaCaT), with high biocompatibility of 92 to 112% cell viability and good hemocompatibility with absorbance ranging from 0.17 to 0.30. The membrane's highest water vapor transmission rate was 1654.7333 ± 0.736 g/m2/day and the highest % porosity was 76%. The membranes supported cellular adhesion and migration, with the highest closure being 68% after 4 days compared with the commercial wound dressings. This membrane exhibited enhanced antimicrobial activity against the pathogens responsible for wound infections. Conclusions: The distinct features of the membranes make them promising wound dressings for treating infected wounds.

Mitigation of Nitrogen Losses in a Plant-Soil System through Incorporation of Nanocellulose and Zinc-Modified Nanocellulose

Most nitrogen (N) applied to plants as fertilizer is lost through leaching. Here, nanocellulose was used in mitigating N leaching loss. Lettuce-cropped soil was treated with unmodified or Zn-modified nanocellulose (1-2% by wt) in combination with NPK, compared with urea and NPK-only treatments. Consecutive leaching, plant growth, plant N uptake, and soil nitrogen retention were assessed. Nanocellulose + NPK significantly (p ≤ 0.05) reduced N leaching, compared with urea and NPK-only. 1-and-2 wt % nanocellulose, as well as Zn-modified 1-and-2 wt % nanocellulose, reduced N leaching by 45, 38, 39, and 49% compared with urea and by 43, 36, 37, and 47% compared with NPK-only, respectively. Nitrogen leached mainly as NO3- (98.4%). Compared with urea and NPK, lettuce shoot mass was significantly (p ≤ 0.05) increased by 30-42% and by 44-57%, respectively, by all nanocellulose treatments, except for the Zn-modified 1 wt % nanocellulose. Leached N negatively correlated to biomass yield. Soil N retention was enhanced by the pristine and Zn-modified nanocelluloses between 27 and 94%. Demonstrably, nanocellulose can be utilized for mitigating N loss in soil and supporting crop production, resource management, and environmental sustainability.

Hybrid Ethylcellulose Polymeric Films: Ag(I)-Based Components and Curcumin as Reinforcing Ingredients for Enhanced Food Packaging Properties

Bio-active ethylcellulose (EC) polymeric films have been obtained by incorporating curcumin (curc) and Ag(I)-based compounds, known for their antioxidant and antimicrobial activity, respectively, within the polymeric matrix. The recently reported Ag(I) coordination polymer, in both its structural forms (α-[(bpy)Ag(OTf)]∞ and β-{[(bpy)Ag][OTf]}∞), and the [(bpy)Ag(OTf)]∞-curc polymeric co-crystal (bpy=2,2'-bipyridine; OTf=trifluoromethanesulfonate) have been selected as Ag(I) species. The hybrid composite films have been prepared through the simple solvent casting method and characterized through Powder X-Ray Diffraction (PXRD), Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscope (SEM), UV-vis spectroscopy. The deep investigation of the film samples highlighted the non-inert behaviour of EC towards these specific active ingredients. Antimicrobial tests showed that EC films embedding the Ag(I)-based compounds present good antimicrobial performance, in particular against Staphylococcus aureus, used as a model of Gram-positive bacteria. In addition, Silver migration tests, performed on the Ag(I)-incorporating EC films, evidenced low values of silver release particularly in the case of the EC films incorporating [(bpy)Ag(OTf)]∞-curc.

Recent advancements in bio-based dielectric and piezoelectric polymers and their biomedical applications

The advent of polymer-based dielectrics marked a significant breakthrough in dielectric materials. However, despite their many advantages, they pose serious environmental threats. Therefore, in recent years, there has been growing interest in bio-based polymers as a sustainable alternative to traditional petroleum-based polymers. Their renewable nature and reduced environmental impact can fulfil the rising demand for eco-friendly substitutes. Beyond their ecological benefits, bio-based polymers also possess distinctive electrical properties that make them extremely attractive in a variety of applications. Considering these, herein, we present recent advancements in bio-based dielectric polymers and nanocomposites. First, the fundamental concepts of dielectric and polymer-based dielectric materials are covered. Then, we will delve into the discussion of recent advancements in the dielectric properties and thermal stability of bio-based polymers, including polylactic acid, polyhydroxyalkanoates, polybutylene succinate, starch, cellulose, chitosan, chitins, and alginates, and their nanocomposites. Other novel bio-based dielectric polymers and their distinct dielectric characteristics have also been pointed out. In an additional section, the piezoelectric properties of these polymers and their recent biomedical applications have been highlighted and discussed thoroughly. In conclusion, this paper thoroughly discusses the recent advances in bio-based dielectric polymers and their potential to revolutionize the biomedical industry while cultivating a more sustainable and greener future.

Alginate based biomaterials for hemostatic applications: Innovations and developments

Development of the efficient hemostatic materials is an essential requirement for the management of hemorrhage caused by the emergency situations to avert most of the casualties. Such injuries require the use of external hemostats to facilitate the immediate blood clotting. A variety of commercially available hemostats are present in the market but most of them are associated with limitations such as exothermic reactions, low biocompatibility, and painful removal. Thus, fabrication of an ideal hemostatic composition for rapid blood clot formation, biocompatibility, and antimicrobial nature presents a real challenge to the bioengineers. Benefiting from their tunable fabrication properties, alginate-based hemostats are gaining importance due to their excellent biocompatibility, with >85 % cell viability, high absorption capacity exceeding 500 %, and cost-effectiveness. Furthermore, studies have estimated that wounds treated with sodium alginate exhibited a blood loss of 0.40 ± 0.05 mL, compared to the control group with 1.15 ± 0.13 mL, indicating its inherent hemostatic activity. This serves as a solid foundation for designing future hemostatic materials. Nevertheless, various combinations have been explored to further enhance the hemostatic potential of sodium alginate. In this review, we have discussed the possible role of alginate based composite hemostats incorporated with different hemostatic agents, such as inorganic materials, polymers, biological agents, herbal agents, and synthetic drugs. This article outlines the challenges which need to be addressed before the clinical trials and give an overview of the future research directions.

Trends in the Incorporation of Antiseptics into Natural Polymer-Based Nanofibrous Mats

Nanofibrous materials represent a very promising form of advanced carrier systems that can be used industrially, especially in regenerative medicine as highly functional bandages, or advanced wound dressings. By incorporation of antimicrobial additives directly into the structure of the nanofiber carrier, the functionality of the layer is upgraded, depending on the final requirement-bactericidal, bacteriostatic, antiseptic, or a generally antimicrobial effect. Such highly functional nanofibrous layers can be prepared mostly by electrospinning technology from both synthetic and natural polymers. The presence of a natural polymer in the composition is very advantageous. Especially in medical applications where, due to the presence of the material close to the human body, the healing process is more efficient and without the occurrence of an unwanted inflammatory response. However, converting natural polymers into nanofibrous form, with a homogeneously distributed and stable additive, is a great challenge. Thus, a combination of natural and synthetic materials is often used. This review clearly summarizes the issue of the incorporation and effectiveness of different types of antimicrobial substances, such as nanoparticles, antibiotics, common antiseptics, or substances of natural origin, into electrospun nanofibrous layers made of mostly natural polymer materials. A section describing the problematic aspects of antimicrobial polymers is also included.

Preparation and Characterization of Biodegradable Sponge-like Cryogel Particles of Chitosan via the Inverse Leidenfrost (iLF) Effect

Chitosan-based cryogel particles were synthesized using the inverse Leidenfrost (iLF) effect, with glutaraldehyde employed as the cross-linker. The resulting cryogels exhibited a sponge-like morphology with micrometer-sized interconnected pores and demonstrated resilience, withstanding up to three compression-release cycles. These characteristics highlight the potential of chitosan cryogels for diverse applications, including adsorption and biomedical uses. We further investigated the influence of varying acetic acid concentrations on the properties of the chitosan cryogels. Our findings revealed that the particle size distribution of the cryogels ranged from 1300 to 2900 μm. As the concentration of acetic acid increased, the swelling degree of the chitosan cryogels decreased, stabilizing at an approximate value of around 6 at 0.03 mol of acetic acid. Additionally, the shift in the absorption peak of the OH and free amino groups from 3261 to 3404 cm-1 confirmed the cross-linking reaction between chitosan and glutaraldehyde.

Biological Activity of Poly(1,3-propanediol citrate) Films and Nonwovens: Mechanical, Thermal, Antimicrobial, and Cytotoxicity Studies

Polymers are of great interest for medical and cosmeceutical applications. The current trend is to combine materials of natural and synthetic origin in order to obtain products with appropriate mechanical strength and good biocompatibility, additionally biodegradable and bioresorbable. Citric acid, being an important metabolite, is an interesting substance for the synthesis of materials for biomedical applications. Due to the high functionality of the molecule, it is commonly used in biomaterials chemistry as a crosslinking agent. Among citric acid-based biopolyesters, poly(1,8-octanediol citrate) is the best known. It shows application potential in soft tissue engineering. This work focuses on a much less studied polyester, poly(1,3-propanediol citrate). Porous and non-porous materials based on the synthesized polyesters are prepared and characterized, including mechanical, thermal, and surface properties, morphology, and degradation. The main focus is on assessing the biocompatibility and antimicrobial properties of the materials.

Synthesis, characterization, and antimicrobial activities of a starch-based polymer

Due to the rise of nosocomial infections and the increasing threat of antibiotic resistance, new techniques are required to combat bacteria and fungi. Functional antimicrobial biodegradable materials developed from low-cost renewable resources like polysaccharides would enable greater applications in this regard. Our group has developed and characterized a new antimicrobial polymer using commercially available N-ethyl piperazine and starch via simple one-pot method. The prepared antimicrobial polymer was characterized by FTIR and NMR. In addition, the thermal properties of the synthesized antimicrobial polymer were examined through TGA and DSC. The antimicrobial potential of the prepared material was investigated using the bacteria, Staphylococcus aureus, Escherichia coli, and Mycobacterium smegmatis and a fungi Candida albicans. The result indicates that, as the amount of polymer increases, the antimicrobial activity also increases. SA-E-NPz exhibited a zone of inhibition in the range of 8-13 mm, and the MIC was found to be < 0.625 mg against all four microbes. The antimicrobial activity of polymer coated on fabric was also studied. Furthermore, the cytotoxicity studied against human fibroblast cell lines showed that the prepared polymer is non-toxic to the cells. The study concluded that the synthesized polymer shows good antimicrobial activity, is non-toxic to human fibroblast cells, and thus can be used for wound dressing or textile applications.

Research progress in preparation, properties, and applications of medical protective fiber materials

A variety of public health events seriously threaten human life and health, especially the outbreak of COVID-19 at the end of 2019 has caused a serious impact on human production and life. Wearing personal protective equipment (PPE) is one of the most effective ways to prevent infection and stop the spread of the virus. Medical protective fiber materials have become the first choice for PPE because of their excellent barrier properties and breathability. In this article, we systematically review the latest progress in preparation technologies, properties, and applications of medical protective fiber materials. We first summarize the technological characteristics of different fiber preparation methods and compare their advantages and disadvantages. Then the barrier properties, comfort, and mechanical properties of the medical protective fiber materials used in PPE are discussed. After that, the applications of medical protective fibers in PPE are introduced, and protective clothing and masks are discussed in detail. Finally, the current status, future development trend, and existing challenges of medical protective fiber materials are summarized.

Essential characteristics improvement of metallic nanoparticles loaded carbohydrate polymeric films - A review

Petroleum-based films have contributed immensely to various environmental issues. Developing green-based films from carbohydrate polymers is crucial for addressing the harms encountered. However, some limitations exist on their property, processibility, and applicability that prohibit their processing for further developments. This review discusses the potential carbohydrate polymers and their sources, film preparation methods, such as solvent-casting, tape-casting, extrusion, and thermo-mechanical compressions for green-based films using various biological polymers with their merits and demerits. Research outcomes revealed that the essential characteristics improvement achieved by incorporating different metallic nanoparticles has significantly reformed the properties of biofilms, including crystallization, mechanical stability, thermal stability, barrier function, and antimicrobial activity. The property-enhanced bio-based films made with nanoparticles are potentially interested in replacing fossil-based films in various areas, including food-packaging applications. The review paves a new way for the commercial use of numerous carbohydrate polymers to help maintain a sustainable green environment.

Biodegradable Polymers and Polymer Composites with Antibacterial Properties

Antibiotic resistance is one of the greatest threats to global health and food security today. It becomes increasingly difficult to treat infectious disorders because antibiotics, even the newest ones, are becoming less and less effective. One of the ways taken in the Global Plan of Action announced at the World Health Assembly in May 2015 is to ensure the prevention and treatment of infectious diseases. In order to do so, attempts are made to develop new antimicrobial therapeutics, including biomaterials with antibacterial activity, such as polycationic polymers, polypeptides, and polymeric systems, to provide non-antibiotic therapeutic agents, such as selected biologically active nanoparticles and chemical compounds. Another key issue is preventing food from contamination by developing antibacterial packaging materials, particularly based on degradable polymers and biocomposites. This review, in a cross-sectional way, describes the most significant research activities conducted in recent years in the field of the development of polymeric materials and polymer composites with antibacterial properties. We particularly focus on natural polymers, i.e., polysaccharides and polypeptides, which present a mechanism for combating many highly pathogenic microorganisms. We also attempt to use this knowledge to obtain synthetic polymers with similar antibacterial activity.

Studies of the Tarragon Essential Oil Effects on the Characteristics of Doped Hydroxyapatite/Chitosan Biocomposites

Due to the emergence of antibiotic-resistant pathogens, the need to find new, efficient antimicrobial agents is rapidly increasing. Therefore, in this study, we report the development of new biocomposites based on zinc-doped hydroxyapatite/chitosan enriched with essential oil of Artemisia dracunculus L. with good antimicrobial activity. Techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR) were used in order to evaluate their physico-chemical properties. Our studies revealed that biocomposite materials with nanometric dimension and homogeneous composition could be obtained through an economic and cost-effective synthesis method. The biological assays demonstrated that ZnHA (zinc-doped hydroxyapatite), ZnHACh (zinc-doped hydroxyapatite/chitosan) and ZnHAChT (zinc-doped hydroxyapatite/chitosan enriched with essential oil of Artemisia dracunculus L.) did not exhibit a toxic effect on the cell viability and proliferation of the primary osteoblast culture (hFOB 1.19). Moreover, the cytotoxic assay also highlighted that the cell morphology of the hFOB 1.19 was not altered in the presence of ZnHA, ZnHACh or ZnHAChT. Furthermore, the in vitro antimicrobial studies emphasized that the samples exhibited strong antimicrobial properties against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 and Candida albicans ATCC 10231 microbial strains. These results are encouraging for the following development of new composite materials with enhanced biological properties that could promote the osteogenic process of bone healing and also exhibit good antimicrobial properties.

Synthesis and characterization of thiazolium chitosan derivative with enhanced antimicrobial properties and its use as component of chitosan based films

In this work, chemical modification of chitosan using cationic thiazolium groups was investigated with the aim to improve water solubility and antimicrobial properties of chitosan. Enzymatic synthesis and ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide (EDC/NHS) chemistry were employed to synthesize and attach to chitosan through the amine groups the molecule bearing thiazolium moieties, quaternized 4-(2-(4-methylthiazol-5-yl) ethoxy)-4-oxobutanoic acid (MTBAQ). On the basis of Fourier transform infrared spectroscopy (FTIR), elemental analysis and solid state nuclear magnetic resonance (ssNMR), around 95 % of the available amine groups of chitosan (of 25 % degree of acetylation) reacted. The resulting derivative was water soluble at physiological pH and exhibit excellent antimicrobial activity against Listeria innocua, Staphylococcus epidermidis, Staphylococcus aureus and Methicillin Resistant S. aureus Gram-positive bacteria (MIC = 8-32 μg/ mL), whereas its efficiency decreases against fungi Candida albicans and Eschericia coli Gram-negative bacterium. Subsequently, the thiazolium chitosan derivative was employed as antimicrobial component (up to 7 wt%) of chitosan/glycerol based films. The incorporation of the chitosan derivative does not modify significantly the characteristics of the film in terms of thermal and mechanical properties, while enhances considerably the antimicrobial activity.

Mechanical Properties of Protein-Based Hydrogels Derived from Binary Protein Mixtures-A Feasibility Study

Hydrogels based on natural polymers such as proteins are considered biocompatible and, therefore, represent an interesting class of materials for application in the field of biomedicine and high-performance materials. However, there is a lack of understanding of the proteins which are able to form hydrogel networks by photoinduced dityrosine crosslinking as well as a profound knowledge of the formed network itself and the mechanisms which are responsible for the resulting mechanical properties of such protein-based hydrogels. In this study, casein, bovine serum albumin, α-amylase, and a hydrophobic elastin-like protein were used to prepare binary protein mixtures with defined concentration ratios. After polymerization, the mechanical properties of the resulting homopolymeric and copolymeric hydrogels were determined using rheological methods depending on the protein shares used. In additional uniaxial compression tests, the fracture strain was shown to be independent of the protein shares, while hydrogel toughness and compressive strength were increased for protein-based hydrogels containing casein.

Effect of the Biopolymer Carrier on Staphylococcus aureus Bacteriophage Lytic Activity

The use of implant materials is always associated with the risk of infection. Moreover, the effectiveness of antibiotics is reduced due to antibiotic-resistant pathogens. Thus, selecting the appropriate alternative antimicrobials for local delivery systems is correlated with successful infection management. We evaluated immobilization of the S. aureus specific bacteriophages in clinically recognized biopolymers, i.e., chitosan and alginate, to control the release profile of the antimicrobials. The high-titre S. aureus specific bacteriophages were prepared from commercial bacteriophage cocktails. The polymer mixtures with the propagated bacteriophages were then prepared. The stability of the S. aureus bacteriophages in the biopolymer solutions was assessed. In the case of chitosan, no plaques indicating the presence of the lytic bacteriophages were observed. The titre reduction of the S. aureus bacteriophages in the Na-alginate was below 1 log unit. Furthermore, the bacteriophages retained their lytic activity in the alginate after crosslinking with Ca2+ ions. The release of the lytic S. aureus bacteriophages from the Ca-alginate matrices in the TRIS-HCl buffer solution (pH 7.4 ± 0.2) was determined. After 72 h-0.292 ± 0.021% of bacteriophages from the Ca-alginate matrices were released. Thus, sustained release of the lytic S. aureus bacteriophages can be ensured.

Nanobacterial Cellulose Production and Its Antibacterial Activity in Biodegradable Poly(vinyl alcohol) Membranes for Food Packaging Applications

Nanobacterial cellulose (NBC) was produced and incorporated into biodegradable poly(vinyl alcohol) (PVA) in different weight ratios to obtain polymer nanocomposite membranes. The physicochemical properties of the membranes were studied using Fourier transform infrared (FTIR) spectroscopy, a universal testing machine (UTM), thermogravimetric analysis (TGA), wide-angle X-ray diffraction (WAXD) techniques, and field emission scanning electron microscopy (FESEM). FTIR confirmed the consolidation of NBC into PVA by exhibiting significant changes in the peaks compared to NBC and PVA individually. The highest tensile strength of 53.33 MPa and 235.30% elongation at break of the membrane M-10 mass % NBC was obtained, illuminating that NBC provides stiffness and PVA imparts elasticity. WAXD revealed that the crystalline nature of the membrane increases up to 10 mass % and decreases beyond it. The effect of NBC on the poly(vinyl alcohol) membranes for food packaging was investigated systematically. Among all the membranes, M-10 mass % NBC was found to be the most suitable for packaging applications. Membranes had antimicrobial activity against food microbes and showed degradability behavior in the soil. The tests on membranes for packaging revealed that fruits were protected from spoilage caused by microorganisms. Hence, the prepared membranes could be used as an alternative to conventional plastics for packaging applications.

Closing the Gap between Bio-Based and Petroleum-Based Plastic through Bioengineering

Bioplastics, which are plastic materials produced from renewable bio-based feedstocks, have been investigated for their potential as an attractive alternative to petroleum-based plastics. Despite the harmful effects of plastic accumulation in the environment, bioplastic production is still underdeveloped. Recent advances in strain development, genome sequencing, and editing technologies have accelerated research efforts toward bioplastic production and helped to advance its goal of replacing conventional plastics. In this review, we highlight bioengineering approaches, new advancements, and related challenges in the bioproduction and biodegradation of plastics. We cover different types of polymers, including polylactic acid (PLA) and polyhydroxyalkanoates (PHAs and PHBs) produced by bacterial, microalgal, and plant species naturally as well as through genetic engineering. Moreover, we provide detailed information on pathways that produce PHAs and PHBs in bacteria. Lastly, we present the prospect of using large-scale genome engineering to enhance strains and develop microalgae as a sustainable production platform.

Composite Coatings of Chitosan and Silver Nanoparticles Obtained by Galvanic Deposition for Orthopedic Implants

In this work, composite coatings of chitosan and silver nanoparticles were presented as an antibacterial coating for orthopedic implants. Coatings were deposited on AISI 304L using the galvanic deposition method. In galvanic deposition, the difference of the electrochemical redox potential between two metals (the substrate and a sacrificial anode) has the pivotal role in the process. In the coupling of these two metals a spontaneous redox reaction occurs and thus no external power supply is necessary. Using this process, a uniform deposition on the exposed area and a good adherence of the composite coating on the metallic substrate were achieved. Physical-chemical characterizations were carried out to evaluate morphology, chemical composition, and the presence of silver nanoparticles. These characterizations have shown the deposition of coatings with homogenous and porous surface structures with silver nanoparticles incorporated and distributed into the polymeric matrix. Corrosion tests were also carried out in a simulated body fluid at 37 °C in order to simulate the same physiological conditions. Corrosion potential and corrosion current density were obtained from the polarization curves by Tafel extrapolation. The results show an improvement in protection against corrosion phenomena compared to bare AISI 304L. Furthermore, the ability of the coating to release the Ag+ was evaluated in the simulated body fluid at 37 °C and it was found that the release mechanism switches from anomalous to diffusion controlled after 3 h.

A Review of Properties of Nanocellulose, Its Synthesis, and Potential in Biomedical Applications

Cellulose is the most venerable and essential natural polymer on the planet and is drawing greater attention in the form of nanocellulose, considered an innovative and influential material in the biomedical field. Because of its exceptional physicochemical characteristics, biodegradability, biocompatibility, and high mechanical strength, nanocellulose attracts considerable scientific attention. Plants, algae, and microorganisms are some of the familiar sources of nanocellulose and are usually grouped as cellulose nanocrystal (CNC), cellulose nanofibril (CNF), and bacterial nanocellulose (BNC). The current review briefly highlights nanocellulose classification and its attractive properties. Further functionalization or chemical modifications enhance the effectiveness and biodegradability of nanocellulose. Nanocellulose-based composites, printing methods, and their potential applications in the biomedical field have also been introduced herein. Finally, the study is summarized with future prospects and challenges associated with the nanocellulose-based materials to promote studies resolving the current issues related to nanocellulose for tissue engineering applications.

Purification of a Hydrophobic Elastin-Like Protein Toward Scale-Suitable Production of Biomaterials

Elastin-like proteins (ELPs) are polypeptides with potential applications as renewable bio-based high-performance polymers, which undergo a stimulus-responsive reversible phase transition. The ELP investigated in this manuscript—ELP[V2Y-45]—promises fascinating mechanical properties in biomaterial applications. Purification process scalability and purification performance are important factors for the evaluation of potential industrial-scale production of ELPs. Salt-induced precipitation, inverse transition cycling (ITC), and immobilized metal ion affinity chromatography (IMAC) were assessed as purification protocols for a polyhistidine-tagged hydrophobic ELP showing low-temperature transition behavior. IMAC achieved a purity of 86% and the lowest nucleic acid contamination of all processes. Metal ion leakage did not propagate chemical modifications and could be successfully removed through size-exclusion chromatography. The simplest approach using a high-salt precipitation resulted in a 60% higher target molecule yield compared to both other approaches, with the drawback of a lower purity of 60% and higher nucleic acid contamination. An additional ITC purification led to the highest purity of 88% and high nucleic acid removal. However, expensive temperature-dependent centrifugation steps are required and aggregation effects even at low temperatures have to be considered for the investigated ELP. Therefore, ITC and IMAC are promising downstream processes for biomedical applications with scale-dependent economical costs to be considered, while salt-induced precipitation may be a fast and simple alternative for large-scale bio-based polymer production.

Simultaneous Release of Silver Ions and 10–Undecenoic Acid from Silver Iron–Oxide Nanoparticles Impregnated Membranes

The bio-medical benefits of silver ions and 10–undecenoic acid in various chemical-pharmaceutical preparations are indisputable, thus justifying numerous research studies on delayed and/or controlled release. This paper presents the effect of the polymer matrix in the simultaneous release of silver ions and 10–undecenoic acid in an aqueous medium of controlled pH and ionic strength. The study took into consideration polymeric matrices consisting of cellulose acetate (CA) and polysulfone (PSf), which were impregnated with oxide nanoparticles containing silver and 10–undecenoic acid. The studied oxide nanoparticles are nanoparticles of iron and silver oxides obtained by an accessible electrochemical method. The obtained results show that silver can be released, simultaneously with 10–undecenoic acid, from an impregnated polymeric membrane, at concentrations that ensure the biocidal and fungicidal capacity. Concentrations of active substances can be controlled by choosing the polymer matrix or, in some cases, by changing the pH of the target medium. In the studied case, higher concentrations of silver ions are released from the polysulfone matrix, while higher concentrations of 10–undecenoic acid are released from the cellulose acetate matrix. The results of the study show that a correlation can be established between the two released target substances, which is dependent on the solubility of the organic compound in the aqueous medium and the interaction of this compound with the silver ions. The ability of 10–undecenoic acid to interact with the silver ion, both through the carboxyl and alkene groups, contributes to the increase in the content of the silver ions transported in the aqueous medium.

Bio-packaging based on cellulose acetate from banana pseudostem and containing Butia catarinensis extracts

Banana (Musa acuminata) pseudostem cellulose was extracted and acetylated (CA) to prepare membranes with potential use as bio-packages. The CA membrane was embedded by Butia seed (CA-BS) or Butia pulp (CA-BP) extracts obtained from Butia catarinenses (Butia). The produced CA, CA-BS, and CA-BP membranes were evaluated for their physical-chemical, mechanical, thermal, and antibacterial properties. The process for obtaining the cellulose yielded a material with about 92.17% cellulose (DS = 2.85). The purity, cellulose degree acetylation, and the incorporation of Butia extracts into the membranes were confirmed by FTIR. The CA-BS and CA-BP membranes showed a smaller contact angle and higher swelling ratio than the CA membrane. Furthermore, Butia seed or pulp extracts reduced the elastic modulus and deformation at break compared to the CA membrane. The DSC analysis suggested the compatibility between sections and the CA matrix, whereas the TGA analysis confirmed the thermal stability of the membranes. Moreover, less than 1% of the Butia seed and pulp extracts were put into a food simulant media from the membrane. Finally, the CA-BS and CA-BP membranes could inhibit the growth of Staphylococcus aureus and Escherichia coli on their surface, confirming the potential use of these membranes as bio-packaging for food preservation.

Marine Biopolymers: Applications in Food Packaging

Marine sources are gaining popularity and attention as novel materials for manufacturing biopolymers such as proteins and polysaccharides. Due to their biocompatibility, biodegradability, and non-toxicity features, these biopolymers have been claimed to be beneficial in the development of food packaging materials. Several studies have thoroughly researched the extraction, isolation, and latent use of marine biopolymers in the fabrication of environmentally acceptable packaging. Thus, a review was designed to provide an overview of (a) the chemical composition, unique properties, and extraction methods of marine biopolymers; (b) the application of marine biopolymers in film and coating development for improved shelf-life of packaged foods; (c) production flaws and proposed solutions for better isolation of marine biopolymers; (d) methods of preparation of edible films and coatings from marine biopolymers; and (e) safety aspects. According to our review, these biopolymers would make a significant component of a biodegradable food packaging system, reducing the amount of plastic packaging used and resulting in considerable environmental and economic benefits.

Contributions of photochemistry to bio-based antibacterial polymer materials

Surgical site infections constitute a major health concern that may be addressed by conferring antibacterial properties to surgical tools and medical devices via functional coatings. Bio-sourced polymers are particularly well-suited to prepare such coatings as they are usually safe and can exhibit intrinsic antibacterial properties or serve as hosts for bactericidal agents. The goal of this Review is to highlight the unique contribution of photochemistry as a green and mild methodology for the development of such bio-based antibacterial materials. Photo-generation and photo-activation of bactericidal materials are illustrated. Recent efforts and current challenges to optimize the sustainability of the process, improve the safety of the materials and extend these strategies to 3D biomaterials are also emphasized.

Antibacterial Polymers Based on Poly(2-hydroxyethyl methacrylate) and Thiazolium Groups with Hydrolytically Labile Linkages Leading to Inactive and Low Cytotoxic Compounds

Herein, we develop a well-defined antibacterial polymer based on poly(2-hydroxyethyl methacrylate) (PHEMA) and a derivative of vitamin B1, easily degradable into inactive and biocompatible compounds. Hence, thiazole moiety was attached to HEMA monomer through a carbonate pH-sensitive linkage and the resulting monomer was polymerized via reversible addition-fragmentation chain transfer (RAFT) polymerization. N-alkylation reaction of the thiazole groups leads to cationic polymer with thiazolium groups. This polymer exhibits excellent antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) with an MIC value of 78 µg mL-1, whereas its degradation product, thiazolium small molecule, was found to be inactive. Hemotoxicity studies confirm the negligible cytotoxicity of the degradation product in comparison with the original antibacterial polymer. The degradation of the polymer at physiological pH was found to be progressive and slow, thus the cationic polymer is expected to maintain its antibacterial characteristics at physiological conditions for a relative long period of time before its degradation. This degradation minimizes antimicrobial pollution in the environment and side effects in the body after eradicating bacterial infection.

Plant-derived nanotherapeutic systems to counter the overgrowing threat of resistant microbes and biofilms

Since antiquity, the survival of human civilization has always been threatened by the microbial infections. An alarming surge in the resistant microbial strains against the conventional drugs is quite evident in the preceding years. Furthermore, failure of currently available regimens of antibiotics has been highlighted by the emerging threat of biofilms in the community and hospital settings. Biofilms are complex dynamic composites rich in extracellular polysaccharides and DNA, supporting plethora of symbiotic microbial life forms, that can grow on both living and non-living surfaces. These enforced structures are impervious to the drugs and lead to spread of recurrent and non-treatable infections. There is a strong realization among the scientists and healthcare providers to work out alternative strategies to combat the issue of drug resistance and biofilms. Plants are a traditional but rich source of effective antimicrobials with wider spectrum due to presence of multiple constituents in perfect synergy. Other than the biocompatibility and the safety profile, these phytochemicals have been repeatedly proven to overcome the non-responsiveness of resistant microbes and films via multiple pathways such as blocking the efflux pumps, better penetration across the cell membranes or biofilms, and anti-adhesive properties. However, the unfavorable physicochemical attributes and stability issues of these phytochemicals have hampered their commercialization. These issues of the phytochemicals can be solved by designing suitably constructed nanoscaled structures. Nanosized systems can not only improve the physicochemical features of the encapsulated payloads but can also enhance their pharmacokinetic and therapeutic profile. This review encompasses why and how various types of phytochemicals and their nanosized preparations counter the microbial resistance and the biofouling. We believe that phytochemical in tandem with nanotechnological innovations can be employed to defeat the microbial resistance and biofilms. This review will help in better understanding of the challenges associated with developing such platforms and their future prospects.

Chemical syntheses of bioinspired and biomimetic polymers toward biobased materials

The rich structures and hierarchical organizations in nature provide many sources of inspiration for advanced material designs. We wish to recapitulate properties such as high mechanical strength, colour-changing ability, autonomous healing and antimicrobial efficacy in next-generation synthetic materials. Common in nature are non-covalent interactions such as hydrogen bonding, ionic interactions and hydrophobic effects, which are all useful motifs in tailor-made materials. Among these are biobased components, which are ubiquitously conceptualized in the space of recently developed bioinspired and biomimetic materials. In this regard, sustainable organic polymer chemistry enables us to tune the properties and functions of such materials that are essential for daily life. In this Review, we discuss recent progress in bioinspired and biomimetic polymers and provide insights into biobased materials through the evolution of chemical approaches, including networking/crosslinking, dynamic interactions and self-assembly. We focus on advances in biobased materials; namely polymeric mimics of resilin and spider silk, mechanically and optically adaptive materials, self-healing elastomers and hydrogels, and antimicrobial polymers.

Highly Elastic Super-Macroporous Cryogels Fabricated by Thermally Induced Crosslinking of 2-Hydroxyethylcellulose with Citric Acid in Solid State

Biopolymer materials have been considered a “green” alternative to petroleum-based polymeric materials. Biopolymers cannot completely replace synthetic polymers, but their application should be extended as much as possible, exploiting the benefits of their low toxicity and biodegradability. This contribution describes a novel strategy for the synthesis of super-macroporous 2-hydroxyethylcellulose (HEC) cryogels. The method involves cryogenic treatment of an aqueous solution of HEC and citric acid (CA), freeze drying, and thermally induced crosslinking of HEC macrochains by CA in a solid state. The effect of reaction temperature (70–180 °C) and CA concentration (5–20 mass % to HEC) on the reaction efficacy and physico-mechanical properties of materials was investigated. Highly elastic cryogels were fabricated, with crosslinking carried out at ≥100 °C. The storage modulus of the newly obtained HEC cryogels was ca. 20 times higher than the modulus of pure HEC cryogels prepared by photochemical crosslinking. HEC cryogels possess an open porous structure, as confirmed by scanning electron microscopy (SEM), and uptake a relatively large amount of water. The swelling degree varied between 17 and 40, depending on the experimental conditions. The degradability of HEC cryogels was demonstrated by acid hydrolysis experiments.

Self-assembly in biobased nanocomposites for multifunctionality and improved performance

Concerns of petroleum dependence and environmental pollution prompt an urgent need for new sustainable approaches in developing polymeric products. Biobased polymers provide a potential solution, and biobased nanocomposites further enhance the performance and functionality of biobased polymers. Here we summarize the unique challenges and review recent progress in this field with an emphasis on self-assembly of inorganic nanoparticles. The conventional wisdom is to fully disperse nanoparticles in the polymer matrix to optimize the performance. However, self-assembly of the nanoparticles into clusters, networks, and layered structures provides an opportunity to address performance challenges and create new functionality in biobased polymers. We introduce basic assembly principles through both blending and in situ synthesis, and identify key technologies that benefit from the nanoparticle assembly in the polymer matrix. The fundamental forces and biobased polymer conformations are discussed in detail to correlate the nanoscale interactions and morphology with the macroscale properties. Different types of nanoparticles, their assembly structures and corresponding applications are surveyed. Through this review we hope to inspire the community to consider utilizing self-assembly to elevate functionality and performance of biobased materials. Development in this area sets the foundation for a new era of designing sustainable polymers in many applications including packaging, construction chemicals, adhesives, foams, coatings, personal care products, and advanced manufacturing.

Curcumin in decellularized goat small intestine submucosa for wound healing and skin tissue engineering

Biomaterials derived from extracellular matrices (ECMs) were extensively used for skin tissue engineering and wound healing. ECM is a complex network of biomolecules (e.g., proteins), which provide organizational support to cells for growth. Thus, ECM could be an ideal biomaterial for fabricating the scaffold. However, oxidative stress and biofilm formation at the wound site remains a major challenge that could be neutralized using herbal ingredients (e.g., curcumin). In this study, ECM was extracted from the biowaste of the goat abattoir by using decellularization. The goat small intestine submucosa (G-SIS) is decellularized to obtain the decellularized G-SIS (DG-SIS) and curcumin (in different concentrations) was incorporated in the DG-SIS to fabricate curcumin-embedded DG-SIS scaffolds. Changes brought by increasing the concentrations of the curcumin in DG-SIS were observed in various properties, including free radical scavenging and antibacterial properties. Results depicted that the scaffolds are porous, biodegradable, biocompatible, antibacterial, and hydrophilic and showed sustained release of curcumin. Besides, it showed free radicals scavenging property. The porosity and hydrophilicity of the scaffolds were decreased with an increase in the curcumin content. However, biodegradability, free radical scavenging, biocompatibility, and antibacterial properties of the scaffolds increased with an increase in the curcumin content. The DG-SIS scaffold containing 1 wt % of curcumin may be a potential biomaterial for wound-healing and skin tissue engineering.

The Future of Functional Clothing for an Improved Skin and Textile Microbiome Relationship

The skin microbiome has become a hot field of research in the last few years. The emergence of next-generation sequencing has given unprecedented insights into the impact and involvement of microbiota in skin conditions. More and more cosmetics contain probiotics or bacteria as an active ingredient, with or without scientific data. This research is also acknowledged by the textile industry. There has been a more holistic approach on how the skin and textile microbiome interacts and how they influence the pH, moisture content and odour generation. To date, most of the ingredients have a broad-spectrum antibacterial action. This manuscript covers the current research and industry developments in the field of skin and textiles. It explores the nature of antimicrobial finishing in textiles which can disrupt the skin microbiome, and the benefits of more natural and microbiome friendly therapies to combat skin conditions, malodour and skin infection.

Advances of peptides for antibacterial applications

In the past few decades, peptide antibacterial products with unique antibacterial mechanisms have attracted widespread interest. They can effectively reduce the probability of drug resistance of bacteria and are biocompatible, so they possess tremendous development prospects. This review provides recent research and analysis on the basic types of antimicrobial peptides (including poly (amino acid)s, short AMPs, and lipopeptides) and factors to optimize antimicrobial effects. It also summarizes the two most important modes of action of antimicrobial peptides and the latest developments in the application of AMPs, including antimicrobial agent, wound healing, preservative, antibacterial coating and others. Finally, we discuss the remaining challenges to improve the antibacterial peptides and propose prospects in the field.

Antibacterial and Antiviral Functional Materials: Chemistry and Biological Activity toward Tackling COVID-19-like Pandemics

The ongoing worldwide pandemic due to COVID-19 has created awareness toward ensuring best practices to avoid the spread of microorganisms. In this regard, the research on creating a surface which destroys or inhibits the adherence of microbial/viral entities has gained renewed interest. Although many research reports are available on the antibacterial materials or coatings, there is a relatively small amount of data available on the use of antiviral materials. However, with more research geared toward this area, new information is being added to the literature every day. The combination of antibacterial and antiviral chemical entities represents a potentially path-breaking intervention to mitigate the spread of disease-causing agents. In this review, we have surveyed antibacterial and antiviral materials of various classes such as small-molecule organics, synthetic and biodegradable polymers, silver, TiO2, and copper-derived chemicals. The surface protection mechanisms of the materials against the pathogen colonies are discussed in detail, which highlights the key differences that could determine the parameters that would govern the future development of advanced antibacterial and antiviral materials and surfaces.

Medical Plaster Enhancement by Coating with Cistus L. Extracts within a Chitosan Matrix: From Natural Complexity to Health Care Simplicity

Our investigation was focused on the preparation and characterization of novel plasters based on Carboxymethyl Chitosan derivative (CMC), to be used for the treatment of radiation dermatitis with Biologic Active Compounds (BACs) in a moist wound-healing environment. After performing the extraction and characterization of BACs from Cistus L., we optimized the BACs/CMC solution for subsequent plaster preparation. Then, plasters were prepared by dip-coating with a different number of layers, and we characterized them by Environmental Scanning Electron Microscopy (ESEM), Contact Angle (CA) and release tests in water for 24 h. Taking into account the flexibility of the plasters and the amount of released BACs after 24 h, the sample obtained after two dip-coating steps (2La) appeared promising in regard to comfortable mechanical properties and active principles administration. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) test performed on keratinocytes cultured in standard medium shows that cells treated with released extract from 2La start to proliferate, extend cellular viability and form colonies typical for epidermal cells.

Catechol-Based Antimicrobial Polymers

Catechol is a key constituent in mussel adhesive proteins and is responsible for strong adhesive property and crosslinking formation. Plant-based polyphenols are also capable of chemical interactions similar to those of catechol and are inherently antimicrobial. This review reports a series of catechol-based antimicrobial polymers classified according to their antimicrobial mechanisms. Catechol is utilized as a surface anchoring group for adhering monomers and polymers of known antimicrobial properties onto various types of surfaces. Additionally, catechol's ability to form strong complexes with metal ions and nanoparticles was utilized to sequester these antimicrobial agents into coatings and polymer matrices. During catechol oxidation, reactive oxygen species (ROS) is generated as a byproduct, and the use of the generated ROS for antimicrobial applications was also introduced. Finally, polymers that utilized the innate antimicrobial property of halogenated catechols and polyphenols were reviewed.

Eco-friendly composites of polyurethane and sheath palm residues

This work prepared eco-friendly biocomposites of polyurethane (PU) and sheath palm residues, using castor oil as a polyol. PU composites filled with natural fibers were prepared at different loading rates: 0 to 20 wt.%. Results indicated that the sheath palm was hydrogen-bonded to PU chains and increased the foams' density. Pore size decreased with an increase in fiber content, from 256 to 116 µm. The fiber's addition improved the ductility of PU foams (compressive modulus from 4.74 to 0.26 MPa) and the foams' crystallinity index (from 5.4 to 15.4%). Compared to pristine PU, the composites showed high hydrophobicity (reaching 123° of contact angle for PU-15%) and thermal stability (Tonset from 96 to 96.3°), and high density (from 41 to 60 kg.m−3), making the developed composites an excellent option for environmental applications, such as oil removal and contaminant adsorption.

Incorporation of Poly(Itaconic Acid) with Quaternized Thiazole Groups on Gelatin-Based Films for Antimicrobial-Active Food Packaging

Poly(itaconic acid) (PIA) was synthesized via conventional radical polymerization. Then, functionalization of PIA was carried out by an esterification reaction with the heterocyclic groups of 1,3-thiazole and posterior quaternization by N-alkylation reaction with iodomethane. The modifications were confirmed by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1H-NMR), as well as ζ-potential measurements. Their antimicrobial activity was tested against different Gram-negative and Gram-positive bacteria. After characterization, the resulting polymers were incorporated into gelatin with oxidized starch and glycerol as film adjuvants, and dopamine as crosslinking agent, to develop antimicrobial-active films. The addition of quaternized polymers not only improved the mechanical properties of gelatin formulations, but also decreased the solution absorption capacity during the swelling process. However, the incorporation of synthesized polymers increased the deformation at break values and the water vapor permeability of films. The antioxidant capacity of films was confirmed by radical scavenging ability and, additionally, those films exhibited antimicrobial activity. Therefore, these films can be considered as good candidates for active packaging, ensuring a constant concentration of the active compound on the surface of the food, increasing products' shelf-life and reducing the environmental impact generated by plastics of petrochemical origin.

Biosafe sustainable antimicrobial encapsulation and coatings for targeted treatment and infections prevention: Preparation for another pandemic

There has been a growing concern for safety and precautions in the wake of coronavirus SARS-CoV2 pandemic also dubbed as COVID-19, which has caused a major impact at a global scale. This has resulted in many industries accelerating at fast pace new biosafety technologies and improving the already existing ones to deal with this highly contagious virus. Most governments across the globe are also mandating policies focusing on increased biosafety to prevent further spread of the virus and protect key workers such as healthcare agents, store employees and police. The COVID-19 pandemic has exposed huge gaps in the healthcare industry that include lack of effective vaccines and medicines, testing of infection, real-time monitoring of the spread of the virus, inadequate protective equipment, and scarcity of protective and intensive care of patients. Some of these may be attributed to a lack of focused research in biosafety materials. As a consequence of the pandemic, a significant body of research activities has therefore focused on biosafety materials that possess unique properties needed for biosafety applications. This graphical review aims to provide a perspective on the usage of bio-based materials to handle the imposing challenges in biosafety. This review investigates existing developments in bio-based antimicrobial encapsulations as an effective measure to deter the growth of COVID-19 virus on surfaces and minimize its spread through surface contact. This will help researchers develop further strategies in material science to focus on contagious pathogens in the future.

Biobased polymers derived from itaconic acid bearing clickable groups with potent antibacterial activity and negligible hemolytic activity

We report the synthesis of new biobased polymers derived from itaconic acid with excellent antibacterial activity against Gram-positive bacteria and very low hemotoxicity.

Anti-biofilm activity of dodecyltrimethylammonium chloride microcapsules against Salmonella enterica serovar Enteritidis and Staphylococcus aureus

Dodecyltrimethylammonium chloride (DTAC) was trapped into maltodextrins/pectin spray dried microcapsules to improve its activity against Salmonella enteritidis and Staphylococcus aureus biofilms. Two different microcapsules were prepared: uncomplexed DTAC-microcapsules (UDM), containing DTAC and maltodextrins; and complexed DTAC-microcapsules (CDM) containing DTAC complexed with pectin and maltodextrins. The minimum inhibitory concentrations (MIC) of both free and microencapsulated DTAC were investigated against S. Enteritidis and S. aureus. The MICs of DTAC were significantly lower when encapsulated. CDM treatment resulted in a 2 and 3.2 log reduction in S. aureus and S. Enteritidis biofilm culturable biomass, respectively. Microencapsulation reduced the cytotoxicity of DTAC by up to 32-fold. Free DTAC and CDM targeted the cell membrane resulting in the leakage of the intracellular molecules and subsequent cell death. The development of DTAC microcapsules reduced the amount of DTAC required to maintain the high standards of cleanliness and hygiene required in the food processing industries.

Functionalization of eggshell membranes with CuO-ZnO based p-n junctions for visible light induced antibacterial activity against Escherichia coli

Biopolymers provide versatile platforms for designing naturally-derived wound care dressings through eco-friendly pathways. Eggshell membrane (ESM), a widely available, biocompatible biopolymer based structure features a unique 3D porous interwoven fibrous protein network. The ESM was functionalized with inorganic compounds (Ag, ZnO, CuO used either separately or combined) using a straightforward deposition technique namely radio frequency magnetron sputtering. The functionalized ESMs were characterized from morphological, structural, compositional, surface chemistry, optical, cytotoxicity and antibacterial point of view. It was emphasized that functionalization with a combination of metal oxides and exposure to visible light results in a highly efficient antibacterial activity against Escherichia coli when compared to the activity of individual metal oxide components. It is assumed that this is possible due to the fact that an axial p-n junction is created by joining the two metal oxides. This structure separates into components the charge carrier pairs promoted by visible light irradiation that further can influence the generation of reactive oxygen species which ultimately are responsible for the bactericide effect. This study proves that, by employing inexpensive and environmentally friendly materials (ESM and metal oxides) and fabrication techniques (radio frequency magnetron sputtering), affordable antibacterial materials can be developed for potential applications in chronic wound healing device area.

Chemical Hydrogels Bearing Thiazolium Groups with a Broad Spectrum of Antimicrobial Behavior

Several hydrogels based on 2-hydroxyethyl methacrylate and a methacrylic monomer containing a thiazole group in its lateral chain have been prepared by thermal polymerization at 60 °C in water solution varying the chemical composition of the gels. The posterior quaternization of the thiazole groups with methyl iodine has rendered positively charged hydrogels with potential antimicrobial activity. This modification has been structurally characterized by infrared spectroscopy, whereas the thermal stability of all hydrogels has been studied by thermal degradation in inert atmosphere. The swelling behavior in distilled water and the rheology of the different hydrogels have been analyzed as a function of 2-(4-methylthiazol-5-yl)ethyl methacrylate (MTA) monomer content as well as its methylation. Finally, the active character of hydrogels against Gram-positive and Gram-negative bacteria and fungi has been evaluated, revealing excellent antimicrobial activity against all tested microorganisms. The methylated hydrogels could be used as potential materials for wound healing or contact lens applications.