Structure-Morphology-Antimicrobial and Antiviral Activity Relationship in Silver-Containing Nanocomposites Based on Polylactide

Hybrid nanocarriers with different densities of silver nanoparticles formation features and antimicrobial properties

This work presents the synthesis and characterization of silica/polyacrylamide hybrid carriers Hyb1 and Hyb2 containing different amounts and lengths of grafted PAAm chains, as well as the formation mechanism, structure, and antibacterial efficacy of their nanocomposites with silver nanoparticles (AgNPs). The main difference between Hyb1 and Hyb2 carriers, such as the thickness and permeability of the PAAm "corona", is highlighted. Using the methods of potentiometry, UV-Vis spectroscopy, TEM and viscometry, the influence of the hybrid structure and concentration of reagents on the two-stage process of reduction of Ag+ ions with sodium borohydride in Hyb1-2 aqueous solutions was established. A strong binding of Ag+ ions to both hybrid matrices at the first stage of reduction and a significant influence of the concentration of Ag-salt (and reducing agent) on the rate of accumulation and yield of AgNPs at the second stage were shown. The presence of two types of AgNPs (internal and external) in the resulting nanocomposites was revealed, resulting from the reduction process both in the internal space of the hybrid "corona" and on its surface. The average size of external AgNPs was larger than internal ones and increased with increasing concentration of Ag-salt (and reducing agent). The role of purification in creating more uniform AgNP/Hyb nanocomposites is demonstrated. High antibacterial effectiveness against S. aureus, E. coli, and P. aeruginosa was established using well diffusion and broth microdilution methods. The obtained MIC values ~ (1.25-2.5)·10-3 kg/m3) are compared to those of potent antibiotics such as ciprofloxacin, ceftriaxone and tetracycline.

Recent Advancements in Sensing of Silver ions by Different Host Molecules: An Overview (2018-2023)

The chemosensors act as powerful tool in the detection of metal ions due to their simplicity, high sensitivity, low cost, low detection limit, rapid photophysical response, and application to the environmental and medical fields. This review article presents an overview for the chemosensing of Ag+ ions based on Calix, MOF, Nanoparticle, COF, Calix, Electrochemical chemosensor published from 2018 to 2023. Here, we have reviewed the sensing of Ag+ ions and summarised the binding response, mechanism, LOD, colorimetric response, adsorption capacity, technique used. The purpose of this review article to provide a detailed summary of the performance of different host chemosensors that are helpful for providing future direction to researchers on Ag+ ion detection and provides path to design effective chemsosensor (simple to synthesize, cost effective, high sensitivity, with more practical application). While studying the related article literature, we came across some challenges and that has been discussed lastly and provided solutions for them.

Enhanced Dielectric Properties and Antibacterial Activity of Natural Rubber by Modification with Poly(Acrylic Acid-Co-Acrylamide) Incorporating Silver Nanoparticles and Titanium Dioxide

This work aims to enhance natural rubber's dielectric properties and antibacterial activity by incorporating silver nanoparticles and titanium dioxide. Deproteinized natural rubber (DPNR) was modified through the graft copolymerization of acrylic acid and acrylamide using N', N'-Methylenebisacrylamide as a crosslinking agent, resulting in poly(acrylic acid-co-acrylamide)-modified, deproteinized natural rubber (MDPNR). This modification facilitated coordination with silver ions and interaction with titanium dioxide. Silver nanoparticles were generated under heat and pressure. Modified natural rubber composites containing silver nanoparticles and titanium dioxide (MDPNR/Ag-TiO2) were prepared. Scanning electron microscopy (SEM) revealed well-distributed silver in the modified natural rubber matrix, while agglomeration of titanium dioxide was observed at a high loading. Both MDPNR and MDPNR/Ag-TiO2 showed high thermal stability compared to DPNR. The MDPNR/Ag-TiO2 composites exhibited higher Tg and lower tan δ, indicating higher stiffness due to the restriction of chain movement compared to that in MDPNR. DPNR exhibited a low dielectric constant, enhanced by poly(acrylic acid-co-acrylamide) modification and silver nanoparticle/titanium dioxide incorporation. Incorporating 0.5 phr of AgNO3 and 2.5 phr of TiO2 in the composites increased the dielectric constant by 1.33 times compared to that of MDPNR. MDPNR showed no antibacterial activity, while the MDPNR/Ag-TiO2 composites exhibited promising antibacterial activity against Staphylococcus aureus and Escherichia coli.

Synergistic Dual Antibacterial Activity of Magnetite Hydrogels Doped with Silver

In this work, we utilized poly-N-isopropylacrylamide (NIPAM), magnetic nanoparticles (MNPs), and silver nitrate to prepare magnetic hydrogel microparticles doped with silver, which exhibited a dual antimicrobial effect. The antibacterial effect of these composites was mediated by the antimicrobial activity of silver and the magnetic hyperthermic induction, which we believe increased biofilm disruption and silver release into the surrounding bacterial biofilms. The prepared particles were characterized by using several analytical techniques. The particles exhibited a porous morphology impregnated evenly with silver nanoparticles, as observed by scanning electron microscopy (SEM). Furthermore, we examined the antibacterial activity of our microparticles against Escherichia coli by determining the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Our findings revealed that the composites demonstrated significant antibacterial activity of up to 81% under magnetic hyperthermia as compared to 45% when samples were heated to the same temperature in a water bath at constant silver concentration. This demonstrates the distinctive inhibitory features of MNPs in enhancing bacterial killing when a magnetic field is applied. The findings of this study lay the groundwork for further exploration of microparticle-based antimicrobial therapies, which can contribute to the development of more advanced wound healing devices and better sterilization methods for medical devices.

Unleashing the power of polymeric nanoparticles - Creative triumph against antibiotic resistance: A review

Antibiotic resistance (ABR) poses a universal concern owing to the widespread use of antibiotics in various sectors. Nanotechnology emerges as a promising solution to combat ABR, offering targeted drug delivery, enhanced bioavailability, reduced toxicity, and stability. This comprehensive review explores concepts of antibiotic resistance, its mechanisms, and multifaceted approaches to combat ABR. The review provides an in-depth exploration of polymeric nanoparticles as advanced drug delivery systems, focusing on strategies for targeting microbial infections and contributing to the fight against ABR. Nanoparticles revolutionize antimicrobial approaches, emphasizing passive and active targeting. The role of various molecules, including small molecules, antimicrobial peptides, proteins, carbohydrates, and stimuli-responsive systems, is being explored in recent research works. The complex comprehension mechanisms of ABR and strategic use of nanotechnology present a promising avenue for advancing antimicrobial tactics, ensuring treatment efficacy, minimizing toxic effects, and mitigating development of ABR. Polymeric nanoparticles, derived from natural or synthetic polymers, are crucial in overcoming ABR. Natural polymers like chitosan and alginate exhibit inherent antibacterial properties, while synthetic polymers such as polylactic acid (PLA), polyethylene glycol (PEG), and polycaprolactone (PCL) can be engineered for specific antibacterial effects. This comprehensive study provides a valuable source of information for researchers, healthcare professionals, and policymakers engaged in the urgent quest to overcome ABR.

Segmental mobility in sustainable copolymers based on poly(lactic acid) blocks built onto poly(butylene succinate) in situ

Two series of newly synthesized sustainable block copolymers based on poly(butylene succinate) (PBSu) and polylactide (PLA) were studied. The copolymers were synthesized by a ring-opening polymerization of PLA in the presence of two initial PBSu of low molar mass. We focused on the effects of the PBSu/PLA ratio (1/99 up to 15/85), chain length and initial PBSu length on the final thermal transitions in the copolymers with an emphasis on molecular mobility/dynamics and subsequently on crystallization. Both aspects are considered relevant to the final materials performance, as well as facilitation of polymer renewability. Calorimetry and dielectric spectroscopy were the main investigation tools. In the amorphous state (i.e., in which the direct effects of copolymer structure are assessable), the segmental mobility of neat PLA was significantly faster in the copolymers. Segmental mobility was monitored via the decrease in the calorimetric and dielectric (α relaxation) glass-transition temperatures, Tg and Tg,diel, respectively. The effect was systematic with an increase in the PBSu/PLA ratio, and was rationalized through the plasticizing role of PBSu (low-Tg component) and facilitated also by the simultaneous lowering of the chain length in the copolymers. Dielectric spectroscopy allowed evaluation of the dynamical fragility (cooperativity) of chains, which was strongly suppressed in the copolymers. This finding suggested an increase in free volume or a gradual increase of interchain distances. This phenomenon could favor the natural enzymatic degradation of the systems (compostability), which is limited in neat PLA. We recorded enhancement of nucleation and the crystalline fraction in the copolymers that was likely connected with faster chain diffusion. Further lowering of the Tg with the implementation of crystallization was noted (which seemed a controversial effect) but which indicated crystallization-induced phase separation.

Exploring nanocomposites for controlling infectious microorganisms: charting the path forward in antimicrobial strategies

Nanocomposites, formed by combining a matrix (commonly polymer or ceramic) with nanofillers (nano-sized inclusions like nanoparticles or nanofibers), possess distinct attributes attributed to their composition. Their unique physicochemical properties and interaction capabilities with microbial cells position them as a promising avenue for infectious disease treatment. The escalating prevalence of multi-drug resistant bacteria intensifies the need for alternative solutions. Traditional approaches involve antimicrobial agents like antibiotics, antivirals, and antifungals, targeting specific microbial aspects. This review presents a comprehensive overview of diverse nanocomposite types and highlights the potential of tailored matrix and antibacterial agent selection within nanocomposites to enhance treatment efficacy and decrease antibiotic resistance risks. Challenges such as toxicity, safety, and scalability in clinical applications are also acknowledged. Ultimately, the convergence of nanotechnology and infectious disease research offers the prospect of enhanced therapeutic strategies, envisioning a future wherein advanced materials revolutionize the landscape of medical treatment.

Overview of Antimicrobial Biodegradable Polyester-Based Formulations

As the clinical complications induced by microbial infections are known to have life-threatening side effects, conventional anti-infective therapy is necessary, but not sufficient to overcome these issues. Some of their limitations are connected to drug-related inefficiency or resistance and pathogen-related adaptive modifications. Therefore, there is an urgent need for advanced antimicrobials and antimicrobial devices. A challenging, yet successful route has been the development of new biostatic or biocide agents and biomaterials by considering the indisputable advantages of biopolymers. Polymers are attractive materials due to their physical and chemical properties, such as compositional and structural versatility, tunable reactivity, solubility and degradability, and mechanical and chemical tunability, together with their intrinsic biocompatibility and bioactivity, thus enabling the fabrication of effective pharmacologically active antimicrobial formulations. Besides representing protective or potentiating carriers for conventional drugs, biopolymers possess an impressive ability for conjugation or functionalization. These aspects are key for avoiding malicious side effects or providing targeted and triggered drug delivery (specific and selective cellular targeting), and generally to define their pharmacological efficacy. Moreover, biopolymers can be processed in different forms (particles, fibers, films, membranes, or scaffolds), which prove excellent candidates for modern anti-infective applications. This review contains an overview of antimicrobial polyester-based formulations, centered around the effect of the dimensionality over the properties of the material and the effect of the production route or post-processing actions.

Bacterial Response to the Surface Aging of PLA Matrices Loaded with Active Compounds

The use of active components in biomaterials improves the properties of existing ones and makes it possible to obtain new devices with antibacterial properties that prevent infections after implantation, thus guaranteeing the success of the implant. In this work, cetyltrimethylammonium bromide (CTAB) and magnesium particles were incorporated into polylactic acid (PLA) films to assess the extent to which progressive aging of the new surfaces resists bacterial colonization processes. For this purpose, the films' surface was characterized by contact angle measurements, ToF-SIMS and AFM, and adhesion, viability and biofilm growth of Staphylococcus epidermidis bacteria on these films were also evaluated. The results show that the inclusion of Mg and CTAB in PLA films changes their surface properties both before and after aging and also modifies bacterial adhesion on the polymer. Complete bactericidal activity is exhibited on non-degraded films and films with CTAB. This antibacterial behavior is maintained after degradation for three months in the case of films containing a higher amount of CTAB.

Revisiting Non-Conventional Crystallinity-Induced Effects on Molecular Mobility in Sustainable Diblock Copolymers of Poly(propylene adipate) and Polylactide

This work deals with molecular mobility in renewable block copolymers based on polylactide (PLA) and poly(propylene adipate) (PPAd). In particular, we assess non-trivial effects on the mobility arising from the implementation of crystallization. Differential scanning calorimetry, polarized light microscopy and broadband dielectric spectroscopy were employed in combination for this study. The materials were subjected to various thermal treatments aiming at the manipulation of crystallization, namely, fast and slow cooling, isothermal melt- and cold-crystallization. Subsequently, we evaluated the changes recorded in the overall thermal behavior, semicrystalline morphology and molecular mobility (segmental and local). The molecular dynamics map for neat PPAd is presented here for the first time. Unexpectedly, the glass transition temperature, T_g, in the amorphous state drops upon crystallization by 8–50 K. The drop becomes stronger with the increase in the PPAd fraction. Compared to the amorphous state, crystallization leads to significantly faster segmental dynamics with severely suppressed cooperativity. For the PLA/PPAd copolymers, the effects are systematically stronger in the cold- as compared to the melt-crystallization, whereas the opposite happens for neat PLA. The local β_PLA relaxation of PLA was, interestingly, recorded to almost vanish upon crystallization. This suggests that the corresponding molecular groups (carbonyl) are strongly involved and immobilized within the semicrystalline regions. The overall results suggest the involvement of either spatial nanoconfinement imposed on the mobile chains within the inter-crystal amorphous areas and/or a crystallization-driven effect of nanophase separation. The latter phase separation seems to be at the origins of the significant discrepancy recorded between the calorimetric and dielectric recordings on T_g in the copolymers. Once again, compared to more conventional techniques such as calorimetry, dielectric spectroscopy was proved a powerful and quite sensitive tool in recording such effects as well as in providing indirect indications for the polymer chains’ topology.