Silver nanoparticles decorated lipase-sensitive polyurethane micelles for on-demand release of silver nanoparticles

Lipase and pH-responsive diblock copolymers featuring fluorocarbon and carboxyl betaine for methicillin-resistant staphylococcus aureus infections

The emergence of multidrug-resistant bacteria along with their resilient biofilms necessitates the development of creative antimicrobial remedies. We designed versatile fluorinated polymer micelles with surface-charge-switchable properties, demonstrating enhanced efficacy against Methicillin-Resistant Staphylococcus Aureus (MRSA) in planktonic and biofilm states. Polymethacrylate diblock copolymers with pendant fluorocarbon chains and carboxyl betaine groups were prepared using reversible addition-fragmentation chain transfer polymerization. Amphiphilic fluorinated copolymers self-assembled into micelles, encapsulating ciprofloxacin in their cores (CIP@FCBMs) for antibacterial and antibiofilm applications. As a control, fluorine-free copolymer micelles loaded with ciprofloxacin (CIP@BCBMs) were prepared. Although both CIP@FCBMs and CIP@BCBMs exhibited pH-responsive surface charges and lipase-triggered drug release, CIP@FCBMs exhibited powerful antimicrobial and antibiofilm activities in vitro and in vivo, attributed to superior serum stability, higher drug loading, enhanced fluorination-facilitated cellular uptake, and lipase-triggered drug release. Collectively, reversing surface charge, on-demand antibiotic release, and fluorination-mediated nanoparticles hold promise for treating bacterial infections and biofilms.

Enhancing Mechanical and Antimicrobial Properties of Dialdehyde Cellulose-Silver Nanoparticle Composites through Ammoniated Nanocellulose Modification

Given the widespread prevalence of viruses, there is an escalating demand for antimicrobial composites. Although the composite of dialdehyde cellulose and silver nanoparticles (DAC@Ag1) exhibits excellent antibacterial properties, its weak mechanical characteristics hinder its practical applicability. To address this limitation, cellulose nanofibers (CNFs) were initially ammoniated to yield N-CNF, which was subsequently incorporated into DAC@Ag1 as an enhancer, forming DAC@Ag1/N-CNF. We systematically investigated the optimal amount of N-CNF and characterized the DAC@Ag1/N-CNF using FT-IR, XPS, and XRD analyses to evaluate its additional properties. Notably, the optimal mass ratio of N-CNF to DAC@Ag1 was found to be 5:5, resulting in a substantial enhancement in mechanical properties, with a 139.8% increase in tensile elongation and a 33.1% increase in strength, reaching 10% and 125.24 MPa, respectively, compared to DAC@Ag1 alone. Furthermore, the inhibition zones against Escherichia coli and Staphylococcus aureus were significantly expanded to 7.9 mm and 15.9 mm, respectively, surpassing those of DAC@Ag1 alone by 154.8% and 467.9%, indicating remarkable improvements in antimicrobial efficacy. Mechanism analysis highlighted synergistic effects from chemical covalent bonding and hydrogen bonding in the DAC@Ag1/N-CNF, enhancing the mechanical and antimicrobial properties significantly. The addition of N-CNF markedly augmented the properties of the composite film, thereby facilitating its broader application in the antimicrobial field.

Preparation of pH-responsive polyurethane nano micelles and their antibacterial application

Considering the differences in pH between bacterial infection microenvironment and normal tissues, a series of pH-responsive drug-release amphiphilic polyurethane copolymers (DPU-g-PEG) have been prepared in this work. Fourier transform infrared (FT-IR) spectroscopy and 1H NMR was selected to detect the structure of the condensed polymers. The DPU-g-PEG amphiphilic copolymers could form stable micelles with a hydrophilic shell of polyethylene glycol (PEG) and a hydrophobic core of polylactic acid (PLA). We loaded a model drug called triclosan onto DPU-g-PEG micelles and studied how pH affects their particle size, Zeta potential, and drug release performance. The results revealed that when exposed to acidic conditions, the surface potential of DPU-g-PEG micelles changed, the micelles' particle size increased, and the drug release performance was significantly enhanced. These results suggested that the micelles prepared in this study can release more antibacterial substances at sites of bacterial infection. Meanwhile, we also investigated the impact of different ratios of soft and hard segments on the properties of micelles, and the results showed that the pH responsiveness of micelles was strongest when the ratio of soft segments (PLLA diol + PEG 2000): 1,6-hexamethylene diisocyanate (HDI): 2,6-Bis-(2-hydroxy-ethyl)-pyrrolo[3,4-f]isoindole-1,3,5,7-tetraone (DMA) = 1: 1.2: 0.2. Furthermore, the results of inhibition zone test, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) all confirmed the antibacterial activity of triclosan-load DPU-g-PEG micelles. In conclusion, the DPU-g-PEG micelles produced in this study have the potential to be used as intelligent drug delivery systems in the biomedical field.

Counterion-induced antibiotic-based small-molecular micelles for methicillin-resistant Staphylococcus aureus infections

A new counterion-induced small-molecule micelle (SM) with surface charge-switchable activities for methicillin-resistant Staphylococcus aureus (MRSA) infections is proposed. The amphiphilic molecule formed by zwitterionic compound and the antibiotic ciprofloxacin (CIP), via a "mild salifying reaction" of the amino and benzoic acid groups, can spontaneously assemble into counterion-induced SMs in water. Through vinyl groups designed on zwitterionic compound, the counterion-induced SMs could be readily cross-linked using mercapto-3, 6-dioxoheptane by click reaction, to create pH-sensitive cross-linked micelles (CSMs). Mercaptosuccinic acid was also decorated on the CSMs (DCSMs) by the same click reaction to afford charge-switchable activities, resulting in CSMs that were biocompatible with red blood cells and mammalian cells in normal tissues (pH 7.4), while having strong retention to negatively charged bacterial surfaces at infection sites, based on electrostatic interaction (pH 5.5). As a result, the DCSMs could penetrate deep into bacterial biofilms and then release drugs in response to the bacterial microenvironment, effectively killing the bacteria in the deeper biofilm. The new DCSMs have several advantages such as robust stability, a high drug loading content (∼ 30%), easy fabrication, and good structural control. Overall, the concept holds promise for the development of new products for clinical application. STATEMENT OF SIGNIFICANCE: We fabricated a new counterion-induced small-molecule micelle with surface charge-switchable activities (DCSMs) for methicillin-resistant Staphylococcus aureus (MRSA) infections. Compared with reported covalent systems, the DCSMs not only have improved stability, high drug loading content (∼ 30%), and good biosafety, but also have the environmental stimuli response, and antibacterial activity of the original drugs. As a result, the DCSMs exhibited enhanced antibacterial activities against MRSA both in vitro and in vivo. Overall, the concept holds promise for the development of new products for clinical application.

Preparation of functional and reactive nanosilver nanogels using oxidized carboxymethyl cellulose

The designing of functional and reactive nanosilver has been carried out by in-situ reduction of silver nitrate using oxidized carboxymethyl cellulose (OCMC). The reduction process is also accompanied by the stabilization of nanoparticles using the OCMC polymer chain, leading to the formation of a structure where nanosilver is entrapped within OCMC gel. The silver nanogels characterized using transmission electron microscopy (TEM) are found to be ∼22 nm. By virtue of the presence of dialdehyde functionality around the silver nanogels, they have the ability to react with a polymer having a complementary functional group. The nanogels have exhibited prominent antimicrobial activity against both gram-negative and gram-positive bacteria. It has been observed that a 0.3 mM concentration of silver nanogel is active in inhibiting bacterial growth. The antibacterial activity of the synthesized Ag nanogels was dose-dependent, with 99.9 % of E. coli and S. aureus destroyed within 5 h at a concentration of 0.4 mM Ag nanogels. The nanogels disrupted the bacterial cell wall and generated reactive oxygen species inside the cell, which resulted in cell death. This investigation provides a very interesting application as a coating for biomedical implants and devices.

Quasi-opsonin conjugated lipase-sensitive micelles activate macrophages against facultative intracellular bacterial infection

Drug resistance caused by facultative intracellular bacteria such as Salmonella typhimurium (S. typhimurium) is still a tough challenge. Bacteria phagocytosed by macrophages have evolved a variety of mechanisms to defend against host attack, and the poor entry of antibiotics into infected macrophages is conducive to the survival of intracellular bacteria. In this report, we prepared a quasi-opsonized chloramphenicol (Chl)-loaded micellar system (B-mLBP-M/Chl) assembled by a bacterial lipase-sensitive polymer with a conjugate of lipopolysaccharide-binding protein (LBP) analog and biotin (B) as a ligand, which could eliminate drug-resistant S. typhimurium with quasi-opsonization via 3 steps: (i) target and release antibiotics on bacteria lipase, (ii) opsonize S. typhimurium to be digested by the macrophage, and (iii) activate the macrophage for fighting. The B-mLBP-M/Chl could target bacterial LPS through mLBP by simulating the N-terminal sequence of native LBP, exhibiting a high ability to target the localized infection site in mice. It could also activate the phagocytosis of macrophages via coupled biotin, cooperating with antibiotics and effectively improving the survival of mice with little pathological damage to tissues. Moreover, compared with native opsonin, B-mLBP does not cause an excessive inflammatory response and could recover homeostasis after exerting the quasi-opsonization by regulating the levels of pro-inflammatory cytokines and anti-inflammatory cytokines. With a universal target site for Gram-negative bacteria and macrophage activation, this B-mLBP-M/Chl could be applied to other bacterial infections in the future. In particular, this analog may also serve as a useful template to design safe artificial opsonin, which could be a ligand for drug delivery systems or prodrugs.

Effect of PEG grafting density on surface properties of polyurethane substrata and the viability of osteoblast and fibroblast cells

The surface of Tecoflex SG-80A Polyurethane (PU) films was modified by grafting polyethylene glycol (PEG) chains at three different molar amounts (0.05, 0.10, and 0.15 mmol). The resulting substrata were characterized by FTIR-ATR, TGA, AFM, SEM and contact angle to assess the surface modifications occurred during the grafting reactions. Osteoblasts and fibroblasts were cultured with PU extracts for 24 h, and their cell viability and morphology were evaluated by CellTiterBlue assay, Crystal Violet staining and Live/Dead assay. FTIR and TGA results indicated that PEG chains were successfully grafted onto PU surfaces, specifically in the hard segment of PU forming allophanate groups as the PEG grafting density increased. SEM and AFM images suggest that PU substrata were partially covered by PEG, increasing the dispersive and basic components of the PU surface energy. It was found that extracts from PEG-grafted polyurethanes increased the osteoblast viability, although fibroblasts viability remained constant regardless PEG grafting density; in spite of this both cells presented a more spread morphology at the lower PEG grafting density. Our results showed that surface energy of PU substrata can be tuned by PEG grafting density; also, the PEG leached tends to increase the pH of culture medium which leads to a higher viability of osteoblasts; nevertheless, PEG grafting density should be optimized to promote a healthy cell morphology as alterations in its morphology were detected at higher concentrations. Graphical abstract.

Stimuli-responsive nanoplatforms for antibacterial applications

The continuously increasing bacterial resistance has become a big threat to public health worldwide, which makes it urgent to develop innovative antibacterial strategies. Nanotechnology-based drug delivery systems are considered as promising strategies in combating bacterial infections which are expected to improve the therapeutic efficacy and minimize the side effects. Unfortunately, the conventional nanodrug delivery systems always suffer from practical dilemmas, including incomplete and slow drug release, insufficient accumulation in infected sites, and weak biofilm penetration ability. Stimuli-responsive nanoplatforms are hence developed to overcome the disadvantages of conventional nanoparticles. In this review, we provide an extensive review of the recent progress of endogenous and exogenous stimuli-responsive nanoplatforms in the antibacterial area, including planktonic bacteria, intracellular bacteria, and bacterial biofilms. Taking advantage of the specific infected microenvironment (pH, enzyme, redox, and toxin), the mechanisms and strategies of the design of endogenous stimuli-responsive nanoplatforms are discussed, with an emphasis on how to improve the therapeutic efficacy and minimize side effects. How to realize controlled drug delivery using exogenous stimuli-responsive nanoplatforms especially light-responsive nanoparticles for improved antibacterial effects is another topic of this review. We especially highlight photothermal-triggered drug delivery systems by the combination of photothermal agents and thermo-responsive materials. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Surface-Charge-Switchable and Size-Transformable Thermosensitive Nanocomposites for Chemo-Photothermal Eradication of Bacterial Biofilms in Vitro and in Vivo

The appearance of multidrug-resistant bacteria and their biofilms presents a serious threat to modern medical systems. Herein, we fabricated a novel gold-nanorod-based chemo-photothermal-integrated antimicrobial platform with surface-charge-switchable and near-infrared (NIR)-induced size-transformable activities that show an enhanced killing efficiency against methicillin-resistant Staphylococcus aureus (MRSA) in both planktonic and biofilm phenotypes. The nanocomposites are prepared by in situ copolymerization using N-isopropyl acrylamide (NIPAM), acrylic acid (AA), and N-allylmethylamine (MAA) as monomers on the surfaces of gold nanorods (GNRs). Ciprofloxacin (CIP) is loaded onto polymer shells of nanocomposites with a loading content of 9.8%. The negatively charged nanocomposites switch to positive upon passive accumulation at the infectious sites, which promotes deep biofilm penetration and bacterial adhesion of the nanoparticles. Subsequently, NIR irradiation triggers the nanocomposites to rapidly shrink in volume, further increasing the depth of biofilm penetration. The NIR-triggered, ultrafast volume shrinkage causes an instant release of CIP on the bacterial surface, realizing the synergistic benefits of chemo-photothermal therapy. Both in vitro and in vivo evidence demonstrate that drug-loaded nanocomposites could eradicate clinical MRSA biofilms. Taken together, the multifunctional chemo-photothermal-integrated antimicrobial platform, as designed, is a promising antimicrobial agent against MRSA infections.

Influence of nanoparticles on the haemostatic balance: between thrombosis and haemorrhage

Maintenance of a delicate haemostatic balance or a balance between clotting and bleeding is critical to human health. Irrespective of administration route, nanoparticles can reach the bloodstream and might interrupt the haemostatic balance by interfering with one or more components of the coagulation, anticoagulation, and fibrinolytic systems, which potentially lead to thrombosis or haemorrhage. However, inadequate understanding of their effects on the haemostatic balance, along with the fact that most studies mainly focus on the functionality of nanoparticles while forgetting or leaving behind their risk to the body's haemostatic balance, is a major concern. Hence, our review aims to provide a comprehensive depiction of nanoparticle-haemostatic balance interactions, which has not yet been covered. The synergistic roles of cells and plasma factors participating in haemostatic balance are presented. Possible interactions and interference of each type of nanoparticle with the haemostatic balance are comprehensively discussed, particularly focusing on the underlying mechanisms. Interactions of nanoparticles with innate immunity potentially linked to haemostasis are mentioned. Various physicochemical characteristics that influence the nanoparticle-haemostatic balance are detailed. Challenges and future directions are also proposed. This insight would be valuable for the establishment of nanoparticles that can either avoid unintended interference with the haemostatic balance or purposely downregulate/upregulate its key components in a controlled manner.

Ciprofloxacin conjugated gold nanorods with pH induced surface charge transformable activities to combat drug resistant bacteria and their biofilms

The ever-growing threat of drug-resistant pathogens and their biofilms based persistent, chronic infections has created an urgent call for new strategies to deal with multidrug resistant bacteria (MDR). Near-infrared (NIR) laser-induced photothermal treatment (PTT) of gold nanorods (AuNRs) disinfects microbes by local heating with low possibility to develop resistant. However, PTT disinfection strategy of AuNRs alone shows less efficiency in killing multidrug resistant strains (i.e. Methicillin-resistant Staphylococcus aureus, MRSA) and their matured biofilms. Herein, a novel synergistic chemo-photothermal integrated antimicrobial platform (P(Cip-b-CB)-AuNRs) was fabricated which show enhanced killing efficiency against MRSA in both planktonic and biofilm phenotypes. Polymethacrylate copolymers with pendant ciprofloxacin (Cip) and the carboxyl betaine groups (P(Cip-b-CB)) were synthesized using reversible addition-fragmentation chain transfer (RAFT) polymerization. P(Cip-b-CB) was decorated onto AuNRs via gold-thiol bond which resulted in AuNRs with acidic-induced surface charge-switchable activities and lipase triggered Cip release properties (P(Cip-b-CB)-AuNRs). The lower pH value and overexpress of lipase are characteristics for microenvironment of microbial infections and their biofilms, which ensure the targeting on, penetration into and on-demand release of Cip from the nanocomposites in bacterial infection sites and their biofilms. The bacterial cell membrane was disrupt by photothermal therapy which could improve its permeability and sensitivity to antibiotics, meanwhile lipase-triggered release of Cip ensures a high concentration of antibiotics at the site of bacterial infection. Besides their NIR induced PTT disinfection activities, the increased local temperature generated by NIR light irradiation accelerated Cip release which further enhanced the antibacterial efficiency, leading to synergistic antibacterial activities of chemo-photothermal therapy. Taken together, the designed synergistic chemo-photothermal integrated antimicrobial platform is a promising antibacterial agent for fighting MDR bacterial infections and their biofilms.

The Role of Silver Nanoparticles in a Treatment Approach for Multidrug-Resistant Salmonella Species Isolates

PURPOSE

The main objective of this study is to investigate the antibacterial activity of silver nanoparticles (AgNPs) against multidrug-resistant Salmonella isolates recovered from diarrheic  sheep and goats.

METHODS

This study used chemical reduction synthesis of AgNPs to evaluate their antimicrobial effects by estimation of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for each isolate using the microplate dilution method and tetrazolium salt reduction test to detect the viability percentage. In vivo treatment efficacy was assessed in mice by determining the viable count of Salmonella Enteritidis recovered from feces and by hematologic, biochemical and histopathologic examinations to confirm that use of AgNPs has no toxic or pathologic effects and to evaluate its ability in tissue regeneration following treatment.

RESULTS

All recovered strains were identified as MDR with a prevalence of 4% and 3.6% in sheep and goats, respectively. The results of TEM, DLS, Zeta potential, and FTIR revealed typical characteristics of the synthesized AgNPs. Silver nanoparticles showed antibacterial activity against all recovered strains with MIC of ≤0.02-0.313 μg/mL (mean average 0.085±0.126 μg/mL) and MBC of 0.078-1.250 μg/mL (average 0.508±0.315 μg/mL). In vivo efficacy of AgNPs was observed by a reduction in the number of viable S. Enteritidis recovered from feces in an S. Enteritidis infected mouse model, with complete shedding stopping between treatment days 4 and 6. Hematologic, serum biochemical, and histopathologic analyses proved the ability of AgNPs to suppress inflammatory reaction caused by S. Enteritidis infection.

CONCLUSION

The study proved the effective ability of AgNPs to fight MDR Salmonella spp. in vitro and in vivo without adverse effects.

Intrinsic stimuli-responsive nanocarriers for smart drug delivery of antibacterial agents-An in-depth review of the last two decades

Antibiotic resistance due to suboptimal targeting and inconsistent antibiotic release at bacterial infection sites has driven the formulation of stimuli-responsive nanocarriers for antibacterial therapy. Unlike conventional nanocarriers, stimuli-responsive nanocarriers have the ability to specifically enhance targeting and drug release profiles. There has been a significant escalation in the design and development of novel nanomaterials worldwide; in particular, intrinsic stimuli-responsive antibiotic nanocarriers, due to their enhanced activity, improved targeted delivery, and superior potential for bacterial penetration and eradication. Herein, we provide an extensive and critical review of pH-, enzyme-, redox-, and ionic microenvironment-responsive nanocarriers that have been reported in literature to date, with an emphasis on the mechanisms of drug release, the nanomaterials used, the nanosystems constructed and the antibacterial efficacy of the nanocarriers. The review also highlights further avenues of research for optimizing their potential and commercialization. This review confirms the potential of intrinsic stimuli-responsive nanocarriers for enhanced drug delivery and antibacterial killing. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Gold nanorods with surface charge-switchable activities for enhanced photothermal killing of bacteria and eradication of biofilm

The gold nanorods (PCB-AuNRs) with pH induced surface charge transform activities were used for photothermal disinfection of planktonic bacteria and eradication of bacterial biofilms.

Recent developments in the use of organic-inorganic nanohybrids for drug delivery

Organic-inorganic nanohybrid (OINH) structures providing a versatile platform for drug delivery with improved characteristics are an area which has gained recent attention. Much effort has been taken to develop these structures to provide a viable treatment options for much alarming diseases such as cancer, bone destruction, neurological disorders, and so on. This review focuses on current work carried out in producing different types of hybrid drug carriers identifying their properties, fabrication techniques, and areas where they have been applied. A brief introduction on understating the requirement for blending organic-inorganic components into a nanohybrid drug carrier is followed with an elaboration given about the different types of OINHs developed currently highlighting their properties and applications. Then, different fabrication techniques are discussed given attention to surface functionalization, one-pot synthesis, wrapping, and electrospinning methods. Finally, it is concluded by briefing the challenges that are remaining to be addressed to obtain multipurpose nanohybrid drug carriers with wider applicability. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies.

Recent advances in the treatment of pathogenic infections using antibiotics and nano-drug delivery vehicles

The worldwide misuse of antibiotics and the subsequent rise of multidrug-resistant pathogenic bacteria have prompted a paradigm shift in the established view of antibiotic and bacterial-human relations. The clinical failures of conventional antibiotic therapies are associated with lengthy detection methods, poor penetration at infection sites, disruption of indigenous microflora and high potential for mutational resistance. One of the most promising strategies to improve the efficacy of antibiotics is to complex them with micro or nano delivery materials. Such materials/vehicles can shield antibiotics from enzyme deactivation, increasing the therapeutic effectiveness of the drug. Alternatively, drug-free nanomaterials that do not kill the pathogen but target virulent factors such as adhesins, toxins, or secretory systems can be used to minimize resistance and infection severity. The main objective of this review is to examine the potential of the aforementioned materials in the detection and treatment of antibiotic-resistant pathogenic organisms.

Effect of capping methods on the morphology of silver nanoparticles: study on the media-induced release of silver from the nanocomposite β-cyclodextrin/alginate

Novel multi-functional nanocomposites were fabricated from polysaccharides, alginate (Alg) and β-cyclodextrin (β-CD) via the ionotropic gelation mechanism.

Silver nanoparticles with pH induced surface charge switchable properties for antibacterial and antibiofilm applications

Silver nanoparticles with pH induced surface charge transform activities were prepared which showed an enhanced antibacterial and antibiofilm efficiency while demonstrated reduced cytotoxicity to mammalian cells.

Bioengineering of Functional Nanosilver Nanogels for Smart Healthcare Systems

Functional designing of nanogels has become an attractive domain of biomedical engineering to develop bioactive materials with innovative features for the human healthcare system. Nanosilver has attracted enormous attention due to its wide antimicrobial spectrum and ability to kill almost all types of bacteria in its vicinity. However, the most crucial challenge for bioscientists is the lack of binding ability of nanosilver with the material surfaces that allow nanosilver to leach out to the surrounding tissue and exert toxicity while the biomaterial is in contact with the living system. Designing nanosilver within a nanogel confinement offers enormous possibilities to develop functional bioactive nanoparticles that may be bonded to any biomaterial surface via the nanogel functionality. This approach requires the proper combination of material science with nanotechnology and biotechnology to innovate interesting domain of functional nanogels with unique features. This work aims at providing a critical review on the current progress, approaches, and vision in designing nanosilver-entrapped nanogel particles with diverse functionality, and their bioactivity against microorganisms for human healthcare devices.

Functional polyurethane nanomicelle with pH-responsive drug delivery property

A new functional pH-responsive polyurethane-based nanomicelle has been developed with BES-Na as the functional monomer, the buffering agent with tertiary amine, and sulfonic acid group was incorporated into the hydrophilic shell as the functional agent, which resulted in polyurethane nanosystem with pH-sensitive property. Folic acid (FA) was chosen as model hydrophobic drug to evaluate the loading and pH-triggered release of the PU micelles in vitro drug loading and release. The drug loading content (LC) and the encapsulation efficiency (EE) for FA-loaded micelles in phosphate-buffered solutions were 7.68% and 27.72%, respectively, and the largest accumulative drug release percentages in pH 6.8 and pH 5.0 were 79.17% and 89.83% in 24 h, respectively. A facile and versatile approach has been provided for the design and fabrication of smart nanovehicles for effective drug delivery and opens a new thought in the design and fabrication of biodegradable polyurethanes for next generation of nanomicellar systems.

An enhancement of antimicrobial efficacy of biogenic and ceftriaxone-conjugated silver nanoparticles: green approach

Of the various methods explored for the synthesis of nanoparticles, biogenesis of silver nanoparticles (AgNPs) received great attention due to their versatile properties. In this report, Daucus carota extract was used for the synthesis of AgNPs and ceftriaxone was conjugated with AgNPs to enhance their antimicrobial efficacy. The conjugated and unconjugated AgNPs were characterized by adopting UV-Vis spectroscopy, FTIR, AFM, DLS, and TEM, which revealed the SPR peak at 420 nm and spherical shaped nanoparticles of 20 nm size, respectively. The antimicrobial efficacies of the unconjugated AgNPs and ceftriaxone-conjugated AgNPs were tested against ceftriaxone-resistant human pathogens, Bacillus cereus, Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The ceftriaxone-conjugated AgNPs showed high inhibitory action (23 mm) than the unconjugated AgNPs (18 mm) at the concentration of 50 μg/mL. Both the unconjugated and ceftriaxone-conjugated AgNPs were found to be non-toxic on EAC cells at 50 μg/mL. The dose-dependent cytotoxic activities were observed on increasing the concentration of the AgNPs. The ceftriaxone-conjugated AgNPs showed high activity than the unconjugated AgNPs. The enhanced activity could be useful to treat ceftriaxone-resistant human pathogens.

Balancing antimicrobial activity with biological safety: bifunctional chitosan derivative for the repair of wounds with Gram-positive bacterial infections

Because of the balance between antimicrobial activity and biological safety, the bifunctional chitosan derivative could control infections and promote healing simultaneously.

Reduction responsive and surface charge switchable polyurethane micelles with acid cleavable crosslinks for intracellular drug delivery

Previously we synthesized redox sensitive polyurethane micelles, core crosslinked by diisocyanates (PU-CCL).

Synthesis of polyurethanes with pendant azide groups attached on the soft segments and the surface modification with mPEG by click chemistry for antifouling applications

Polyurethane with pendant azide groups on the soft segment (PU-GAP) was prepared in this study to further increase the content of reactive azide groups and improve their surfaces enrichment for further functionalization. Polymer diols with pendant azide groups (GAP) were prepared by transforming the pendant chlorine groups at polyepichlorohydrin (PECH) into azide groups with sodium azide. The prepared PECH, GAP and PU-GAP was characterized by GPC, ¹H NMR and FTIR. Propargylic mPEG (mPEG-alkyne) was used as model surface modification reagents which was grafted on the prepared azido containing polyurethane films via click chemistry. The surface morphology, chemical composition and wettabilities were studied by SEM, XPS and water contact angle (WCA) analysis, respectively. SEM results demonstrated different surface topologies between mPEG modified PU surface and original PU surface. XPS and WCA analysis proved the successful grafting of mPEG on the pendant azide groups of PUs. The mPEG modified PU surfaces demonstrated good antifouling activities against model bacteria and mPEG with larger molecular weights modified surfaces showed better resistance efficiency to attachment of bacteria. Therefore, the surface reactive polyurethane we prepared can be a universal platform for further functionalization according actual applications.

Polyurethane with pendant azide groups on the soft segment which can be an universal platform for further functionalization according actual applications.

High-performance anionic waterborne polyurethane/Ag nanocomposites with excellent antibacterial property via in situ synthesis of Ag nanoparticles

High-performance anionic waterborne polyurethane/Ag nanocomposites synthesizedvia in situreduction.