Mannose-Modificated Polyethylenimine: A Specific and Effective Antibacterial Agent against Escherichia coli

Inherent antibacterial properties of mannose-containing polynorbornene glycomaterials

Monosaccharides are typically employed as targeting ligands in antimicrobial polymers, yet we discovered that certain glycopolymers prepared by ring-opening metathesis polymerization display inherent antibacterial activity, despite lacking conventional antimicrobial groups. Mannose-functionalized polymers proved potent against Escherichia coli, which could be rescued by adding excess mannose to the growth medium.

Sweet regulation - The emerging immunoregulatory roles of hexoses

BACKGROUND

It is widely acknowledged that dietary habits have profound impacts on human health and diseases. As the most important sweeteners and energy sources in human diets, hexoses take part in a broad range of physiopathological processes. In recent years, emerging evidence has uncovered the crucial roles of hexoses, such as glucose, fructose, mannose, and galactose, in controlling the differentiation or function of immune cells.

AIM OF REVIEW

Herein, we reviewed the latest research progresses in the hexose-mediated modulation of immune responses, provided in-depth analyses of the underlying mechanisms, and discussed the unresolved issues in this field.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Owing to their immunoregulatory effects, hexoses affect the onset and progression of various types of immune disorders, including inflammatory diseases, autoimmune diseases, and tumor immune evasion. Thus, targeting hexose metabolism is becoming a promising strategy for reversing immune abnormalities in diseases.

Accessible preparation of a novel nitrogen‑phosphorus synergetic nanocellulose-based flame retardant with excellent char-forming ability for enhancing the anti-melting droplet property of PA66

Developing eco-friendly and effective flame retardants is crucial for enhancing the fire resistance of polymeric materials. This study developed a novel nitrogen‑phosphorus (NP) synergistic nanocellulose-based flame retardant (CNC-PEI-PA) by grafting polyethyleneimine (PEI) and phytic acid (PA) onto the CNC. CNC-PEI-PA demonstrated remarkable thermal stability, char-forming ability, and antibacterial activity. Notably, the height of the intumescent char layer for CNC-PEI-PA increased by 700 %, and the char yield improved from 24.5 % to 45.0 % compared to CNC. Introducing CNC-PEI-PA into polyamide 66 (PA66) raised its maximum decomposition temperature to 470.0 °C and increased the char yield by nearly 330 %. More importantly, the quick formation of a dense intumescent char layer functioned as a robust protective barrier, enhancing the flame retardancy of PA66 while also greatly improving its anti-melting droplet property. The successful preparation of NP synergistic bio-based flame retardants through a facile and eco-friendly synthetic route shows their significant potential to enhance both the flame retardancy and anti-melting droplet properties of polymer materials.

Unlocking the Antibacterial Potential of Naphthalimide-Coumarins to Overcome Drug Resistance with Antibiofilm and Membrane Disruption Ability against Escherichia coli

Resistance by bacteria to available antibiotics is a threat to human health, which demands the development of new antibacterial agents. Considering the prevailing conditions, we have developed a library of new naphthalimide-coumarin moieties as broad-spectrum antibacterial agents to fight against awful drug resistance. Preliminary studies indicate that compounds 8e and 8h display excellent antibacterial activity against Escherichia coli, exceeding the performance of marketed drug amoxicillin. These drug candidates effectively inhibit biofilm formation and disrupt the biofilm virulence factor, which is accountable for the formation of strong biofilm. In addition to this, both compounds exhibit fast bactericidal properties, thus shortening the time of treatment and resisting the emergence of drug resistance for up to 20 passages. Further, biofunctional evaluation reveals that both compounds effectively disrupt the membrane, causing the leakage of cytoplasmic contents and loss in metabolic activity. Both compounds 8e and 8h efficiently induce the ROS, leading to the oxidation of GSH to GSSG, decreasing the GSH activity of the cell, and causing oxidative damage to the cells. Additionally, both compounds effectively bind with DNA to block DNA replication and form supramolecular complexes, thus exhibiting antibacterial activity. Moreover, these compounds readily bind human serum albumin with high binding constants and can be transported to the target site easily. These findings reveal that newly synthesized naphthalimide-coumarin conjugates have the potential to build as potent antibacterial agents and can be used further for clinical trials.

Soft nanoparticles as antimicrobial agents and carriers of microbiocides for enhanced inhibition activity

Antibiotic resistance continues to pose significant health challenges. Considering severe limitations in the discovery and supply of new antibiotics, there is an unmet need to design alternative and more effective strategies for addressing this global issue. Use of polymeric nanoparticles with cationic shell surfaces offers a highly promising approach to coupling their inherent bactericidal action with sustained delivery of small lipophilic microbicides. We have utilized this platform for assembling multi-tasking soft core-shell nanoparticles from star polymers with the desired asymmetric arm composition. These stable nanoparticles with low critical micelle concentration imparted intrinsic antimicrobial potency due to high positive charge density in the corona, as well as the loading of active biocidal agents (such as curcumin and terbinafine) for potential dual and coadjuvant inhibition. This strategic combination allows for both immediate (direct contact) and extended (drug delivery) antibacterial activities for better therapeutic efficacy. Micellar nanoparticles with and without therapeutic cargo were highly efficient against both Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis), representative Gram-negative and Gram-positive bacteria, respectively. Interestingly, we observed bacteria- and concentration-dependent effects, in which higher concentrations of charged nanoparticles were more effective against E. coli, whereas B. subtilis was inhibited only at lower concentrations. This work highlights a valuable platform to achieve combination therapy through nanoparticles with charged coronas and delivery of potent therapeutics to overcome antimicrobial resistance.

Antimicrobial activity and structure-activity relationships of molecules containing mono- or di- or oligosaccharides: An update

Bacterial infections are the second leading cause of death worldwide, and the evolution and widespread distribution of antibiotic-resistance elements in bacterial pathogens exacerbate the threat crisis. Carbohydrates participate in bacterial infection, drug resistance and the process of host immune regulation. Numerous antimicrobials derived from carbohydrates or contained carbohydrate scaffolds that are conducive to an increase in pathogenic bacteria targeting, the physicochemical properties and druggability profiles. In the paper, according to the type and number of sugar residues contained in antimicrobial molecules collected from the literatures ranging from 2014 to 2024, the antimicrobial activities, action mechanisms and structure-activity relationships were delineated and summarized, for purpose to provide the guiding template to select the type and size of sugars in the design of oligosaccharide-based antimicrobials to fight the looming antibiotic resistance crisis.

Development of a Sensitive Colorimetric Indicator for Detecting Beef Spoilage in Smart Packaging

This study aimed to fabricate and characterize a novel colorimetric indicator designed to detect ammonia (NH3) and monitor meat freshness. The sensing platform was constructed using electrospun nanofibers made from polylactic acid (PLA), which were then impregnated with anthocyanins as a natural pH-sensitive dye, extracted from red cabbage. This research involved investigating the relationship between the various concentrations of anthocyanins and the colorimetric platform's efficiency when exposed to ammonia vapor. Scanning electron microscope (SEM) results were used to examine the morphology and structure of the nanofiber mats before and after the dip-coating process. The study also delved into the selectivity of the indicator when exposed to various volatile organic compounds (VOCs) and their stability under extreme humidity levels. Furthermore, the platform's sensitivity was evaluated as it encountered ammonia (NH3) in concentrations ranging from 1 to 100 ppm, with varying dye concentrations. The developed indicator demonstrated an exceptional detection limit of 1 ppm of MH3 within just 30 min, making it highly sensitive to subtle changes in gas concentration. The indicator proved effective in assessing meat freshness by detecting spoilage levels in beef over time. It reliably identified spoilage after 10 h and 7 days, corresponding to bacterial growth thresholds (107 CFU/mL), both at room temperature and in refrigerated environments, respectively. With its simple visual detection mechanism, the platform offered a straightforward and user-friendly solution for consumers and industry professionals alike to monitor packaged beef freshness, enhancing food safety and quality assurance.

A Simple and Cost-Effective FeCl3-Catalyzed Functionalization of Cellulose Nanofibrils: Toward Adhesive Nanocomposite Materials for Medical Implants

In the present work, we explored Lewis acid catalysis, via FeCl3, for the heterogeneous surface functionalization of cellulose nanofibrils (CNFs). This approach, characterized by its simplicity and efficiency, facilitates the amidation of nonactivated carboxylic acids in carboxymethylated cellulose nanofibrils (c-CNF). Following the optimization of reaction conditions, we successfully introduced amine-containing polymers, such as polyethylenimine and Jeffamine, onto nanofibers. This introduction significantly enhanced the physicochemical properties of the CNF-based materials, resulting in improved characteristics such as adhesiveness and thermal stability. Reaction mechanistic investigations suggested that endocyclic oxygen of cellulose finely stabilizes the transition state required for further functionalization. Notably, a nanocomposite, containing CNF and a branched low molecular weight polyethylenimine (CNF-PEI 800), was synthesized using the catalytic reaction. The composite CNF-PEI 800 was thoroughly characterized having in mind its potential application as coating biomaterial for medical implants. The resulting CNF-PEI 800 hydrogel exhibits adhesive properties, which complement the established antibacterial qualities of polyethylenimine. Furthermore, CNF-PEI 800 demonstrates its ability to support the proliferation and differentiation of primary human osteoblasts over a period of 7 days.

Effective antibacterial agents in modern wound dressings: a review

Wound infections are a significant concern in healthcare, leading to long healing times. Traditional approaches for managing wound infections rely heavily on systemic antibiotics, which are associated with the emergence of antibiotic-resistant bacteria. Therefore, the development of alternative antibacterial materials for wound care has gained considerable attention. In today's world, new generations of wound dressing are commonly used to heal wounds. These new dressings keep the wound and the area around it moist to improve wound healing. However, this moist environment can also foster an environment that is favorable for the growth of bacteria. Excessive antibiotic use poses a significant threat to human health and causes bacterial resistance, so new-generation wound dressings must be designed and developed to reduce the risk of infection. Wound dressings using antimicrobial compounds minimize wound bacterial colonization, making them the best way to avoid open wound infection. We aim to provide readers with a comprehensive understanding of the latest advancements in antibacterial materials for wound management.

Understanding the mechanism of polyethyleneimine-mediated cell disintegration and protein extraction in E. coli: The role of floc network formation and PEI molecular weight

Cell disintegration and protein extraction are crucial steps in downstream process development for biopharmaceuticals produced in E. coli. In this study, we explored the extraction mechanism of polyethyleneimine (PEI) at the cellular level and characterized the floc network that is formed upon PEI addition by Focused Beam Reflectance Measurement and Dispersion Analyzer. PEI disintegrates the cells by detachment of the outer membrane allowing protein to diffuse into the interspace of the flocs. Protein release into the supernatant occurs by diffusion out of the floc network. We could show that the type and concentrations of PEIs with varying molecular weight determines the floc properties and thus the extraction efficiency. We could demonstrate why optimal conditions, using 70 kDa PEI at 0.25 g/g cell dry mass, lead to efficient extraction while at suboptimal conditions extraction is almost negligible. Our findings provide valuable insights into the relationship between floc properties and PEI-driven protein extraction, with potential applications in bioprocessing and biotechnology.

Tackling catheter-associated urinary tract infections with next-generation antimicrobial technologies

Urinary catheters and other medical devices associated with the urinary tract such as stents are major contributors to nosocomial urinary tract infections (UTIs) as they provide an access path for pathogens to enter the bladder. Considering that catheter-associated urinary tract infections (CAUTIs) account for approximately 75% of UTIs and that UTIs represent the most common type of healthcare-associated infections, novel anti-infective device technologies are urgently required. The rapid rise of antimicrobial resistance in the context of CAUTIs further highlights the importance of such preventative strategies. In this review, the risk factors for pathogen colonization in the urinary tract are dissected, taking into account the nature and mechanistics of this unique environment. Moreover, the most promising next-generation preventative strategies are critically assessed, focusing in particular on anti-infective surface coatings. Finally, emerging approaches in this field and their likely clinical impact are examined.

PEI-based functional materials: Fabrication techniques, properties, and biomedical applications

Cationic polymers have recently attracted considerable interest as research breakthroughs for various industrial and biomedical applications. They are particularly interesting due to their highly positive charges, acceptable physicochemical properties, and ability to undergo further modifications, making them attractive candidates for biomedical applications. Polyethyleneimines (PEIs), as the most extensively utilized polymers, are one of the valuable and prominent classes of polycations. Owing to their flexible polymeric chains, broad molecular weight (MW) distribution, and repetitive structural units, their customization for functional composites is more feasible. The specific beneficial attributes of PEIs could be introduced by purposeful functionalization or modification, long service life, biocompatibility, and distinct geometry. Therefore, PEIs have significant potential in biotechnology, medicine, and bioscience. In this review, we present the advances in PEI-based nanomaterials, their transfection efficiency, and their toxicity over the past few years. Furthermore, the potential and suitability of PEIs for various applications are highlighted and discussed in detail. This review aims to inspire readers to investigate innovative approaches for the design and development of next-generation PEI-based nanomaterials possessing cutting-edge functionalities and appealing characteristics.

Enhanced Antibacterial Activity against Escherichia coli Based on Cationic Carbon Dots Assembling with 5-Aminolevulinic Acid

Carbon dots (CDs) with positive surface charges are considered one of the encouraging nanomedications for antibacterial applications. However, due to the distinctive membrane structure of Gram-negative bacteria, cationic CDs with relatively high concentrations are usually required for effective treatment, which might bring out serious safety issues at high doses. Therefore, it is of substantial significance to improve the killing efficiency of cationic CDs on Gram-negative bacteria at appropriately low concentrations. In this work, optimized cationic CDs (bPEI25 000-CDs) were prepared via a hydrothermal method with citric acid and branched PEI25000, which offered a positive surface potential, elimination abilities against Escherichia coli, and relatively high biosafety. The optimized bPEI25 000-CDs can further assemble with the clinical photodynamic therapy (PDT) drug 5-aminolevulinic acid (5-ALA) through electrostatic interaction. Moreover, compared with bPEI25 000-CDs and 5-ALA, the bacterial survival rate was significantly reduced by the ALA-bPEI25 000-CD-induced PDT effect. Even when the dose of bPEI25 000-CD carrier was halved, the bacterial survival could be reduced by 44.4% after light exposure compared to those incubated in the dark. The investigation of the bacterial morphology, membrane potential, and intracellular ROS production suggested that the enhanced antibacterial activity may be due to the membrane dysfunction and cell damage resulting from the high interaction between positively charged ALA-bPEI25 000-CDs and the bacterial cell membrane. Meanwhile, the cationic ALA-bPEI25 000-CDs may facilitate the cellular uptake of 5-ALA, resulting in a more efficient PDT effect. In summary, the antibacterial strategy proposed in this study will provide a novel approach for expanding the application of CD-based nanomedications.

Glucose oxidase and ruthenium nanorods-embedded self-healing polyvinyl alcohol/polyethylene imine hydrogel for simultaneous photothermal/photodynamic/starvation therapy and skin reconstruction

Tumor recurrence and wound healing represent significant burdens for tumor patients after the surgical removal of melanomas. Wound dressings with wound healing and anticancer therapeutic abilities could help to solve these issues. Thus, a hybrid hydrogel made of polyvinyl alcohol (PVA) and polyethylene imine (PEI) was prepared by cross-linking imine bond and boronic acid bond. This hydrogel was loaded with ruthenium nanorods (Ru NRs) and glucose oxidase (GOx) and named as nanocomposite hydrogel (Ru/GOx@Hydrogel), exhibiting remarkable photothermal/photodynamic/starvation antitumor therapy and wound repair abilities. Ru NRs are bifunctional phototherapeutic agents that simultaneously exhibit intrinsic photothermal and photodynamic functions. Three-dimensional composite hydrogel loaded with GOx can also consume glucose in the presence of O2 during tumor starvation therapy. Near-infrared (NIR) light-triggered hyperthermia can not only promote the consumption of glucose, but also facilitate the ablation of residual cancer cells. The antitumor effect of the Ru/GOx@Hydrogel resulted in significant improvements, compared to those observed with either phototherapy or starvation therapy alone. Additionally, the postoperative wound was substantially healed after treatment with Ru/GOx@Hydrogel and NIR irradiation. Therefore, the Ru/GOx@Hydrogel can be used as a multi-stimulus-responsive nanoplatform that could facilitate on-demand controlled drug release, and be used as a promising postoperative adjuvant in combination therapy.

Boric Acid-Functionalized Carbon Dots as a High-Performance Antibacterial Agent against Escherichia coli

Bacterial infections and antibiotic abuse are a global threat to human health. In recent years, there has been a boom in research on antimicrobial agents with low toxicity and efficient nanomaterials. Boric acid-functionalized carbon dots (B-CDs) with negative surface charge were synthesized by the hydrothermal method. Covalent bonds were formed between the boric acid groups and the cis-diol groups of the polysaccharide in the bacterial cell wall, and numerous B-CDs were trapped on the bacterial surface. In the experiments of antibacterial activity, B-CDs presented strong bactericidal activity against Escherichia coli (E. coli) with a minimum bactericidal concentration of 12.5 μg/mL. The antibacterial mechanism suggested that B-CDs entered the cell interior by diffusion and posed significant damage to the double helix structure of E. coli DNA. Furthermore, B-CDs exhibited low toxicity. The results demonstrated that the novel antimicrobial B-CDs not only fought against E. coli infection and antibiotic misuse but also provided new ideas for safe and effective antimicrobial agents of carbon nanomaterials.

Highly stable and fast-dissolving ascorbic acid-loaded microneedles

OBJECTIVES

Ascorbic acid has many benefits to the skin. Numerous attempts to promote its topical delivery show great challenges since its chemical instability and poor skin impermeability. Microneedle delivery is a simple, safe, painless and effective means to deliver therapeutic or nourishing molecules into the skin. The purpose of this study was twofold: (a) to develop a new formulation of ascorbic acid-loaded microneedles to enhance ascorbic acid stability by investigating an optimal amount of polyethyleneimine as an additive to the dextran-based microneedle formulation and (b) to assess microneedle properties in terms of dissolving rate, skin penetration ability, biocompatibility and antimicrobial activity.

METHODS

The microneedles formulated with ascorbic acid and varied polyethyleneimine concentrations were fabricated and subsequently tested for ascorbic acid stability using 2,2-diphenyl-1-picrylhydrazyl assay. The dissolution rate and skin penetration depth were investigated in porcine skin and the reconstructed human full-thickness skin model respectively. The skin irritation tests were done according to the Organisation for Economic Co-operation and Development Test Guideline No. 439. An antimicrobial disc susceptibility test was performed against Escherichia coli, Staphylococcus aureus and Staphylococcus epidermidis.

RESULTS

Among varied amounts of 0%, 1.5%, 3.0% and 4.5% (w/v), the 3.0% polyethyleneimine showed the most desirable characteristics, including well-preserved shape integrity after demoulding, significantly improved stability of ascorbic acid (p < 0.001) from 33% to 96% antioxidant activity after 8 weeks of storage at 40°C, increased dissolving rate (p < 0.001) by being completely dissolved within 2 min after the skin insertion, passing skin penetration and biocompatibility tests as well as having a broad spectrum of antimicrobial property.

CONCLUSION

With a safety profile and enhanced properties, the new formulation of ascorbic acid-loaded microneedles shows outstanding potential as commercially available cosmetics and healthcare products.

Mannose facilitates Trichinella spiralis expulsion from the gut and alleviates inflammation of intestines and muscles in mice

Trichinellosis is a major zoonotic parasitosis which is a vital risk to meat food safety. It is requisite to exploit new strategy to interdict food animal Trichinella infection and to obliterate Trichinella from food animals to ensure meat safety. Mannose is an oligosaccharide that specifically binds to the carbohydrate-recognition domain of C-type lectin; it has many physiological functions including reliving inflammation and regulating immune reaction. The purpose of this study was to investigate the suppressive role of mannose on T. spiralis larval invasion and infection, its effect on intestinal and muscle inflammation, and immune responses after challenge. The results showed that compared to the saline-treated infected mice, the mannose-treated infected mice had less intestinal adult and muscle worm burdens, mild inflammation of intestine and muscle of infected mice. The levels of specific anti-Trichinella IgG (IgG1/IgG2a), IgA and sIgA in mannose-treated infected mice were obviously inferior to saline-treated infected mice (P < 0.01). Furthermore, the levels of two cytokines (IFN-γ and IL-4) in mannose-treated infected mice were also significantly lower than the saline-treated infected mice (P < 0.01). The protective effect of the mannose against Trichinella infection might be not related to specific antibody and cellular immune responses. The above results demonstrated that mannose could be considered as a novel adjuvant therapeutic agent for anti-Trichinella drugs to block larval invasion at early stage of Trichinella infection.

Engineering of inhalable nano-in-microparticles for co-delivery of small molecules and miRNAs

In this study, novel Trojan particles were engineered for direct delivery of doxorubicin (DOX) and miR-34a as model drugs to the lungs to raise local drug concentration, decrease pulmonary clearance, increase lung drug deposition, reduce systemic side effects, and overcome multi-drug resistance. For this purpose, targeted polyelectrolyte nanoparticles (tPENs) developed with layer-by-layer polymers (i.e., chitosan, dextran sulfate, and mannose-g-polyethyleneimine) were spray dried into a multiple-excipient (i.e., chitosan, leucine, and mannitol). The resulting nanoparticles were first characterized in terms of size, morphology, in vitro DOX release, cellular internalization, and in vitro cytotoxicity. tPENs showed comparable cellular uptake levels to PENs in A549 cells and no significant cytotoxicity on their metabolic activity. Co-loaded DOX/miR-34a showed a greater cytotoxicity effect than DOX-loaded tPENs and free drugs, which was confirmed by Actin staining. Thereafter, nano-in-microparticles were studied through size, morphology, aerosolization efficiency, residual moisture content, and in vitro DOX release. It was demonstrated that tPENs were successfully incorporated into microspheres with adequate emitted dose and fine particle fraction but low mass median aerodynamic diameter for deposition into the deep lung. The dry powder formulations also demonstrated a sustained DOX release at both pH values of 6.8 and 7.4.

Dual Coordination between Stereochemistry and Cations Endows Polyethylene Terephthalate Fabrics with Diversiform Antimicrobial Abilities for Attack and Defense

Modification of fabrics by stereochemical antiadhesion strategies is an emerging approach to antimicrobial fabric finishing. However, a purely antiadhesive fabric cannot avoid the passive adhesion of pathogenic microorganisms. To address this issue, borneol 4-formylbenzoate (BF) with a stereochemical structure is introduced into a cationic polymer PEI-modified PET fabric by a simple two-step method. The obtained fabric exhibits remarkable features of high bactericidal activity, excellent resistance to bacterial adhesion, desirable fungal repellent performance, and low cytotoxicity. More impressively, this modified fabric not only effectively reduces microbial contamination during food preservation but also plays a role in avoiding infection and accelerating wound healing in the mouse wound model. The dual coordination between stereochemistry and cations is validated as a viable "attack and defense" antimicrobial strategy, providing an effective guide for diversiform antimicrobial designs.

Mannose: a potential saccharide candidate in disease management

There are a plethora of antibiotic resistance cases and humans are marching towards another big survival test of evolution along with drastic climate change and infectious diseases. Ever since the first antibiotic [penicillin], and the myriad of vaccines, we were privileged to escape many infectious disease threats. The survival technique of pathogens seems rapidly changing and sometimes mimicking our own systems in such a perfect manner that we are left unarmed against them. Apart from searching for natural alternatives, repurposing existing drugs more effectively is becoming a familiar approach to new therapeutic opportunities. The ingenious use of revolutionary artificial intelligence-enabled drug discovery techniques is coping with the speed of such alterations. D-Mannose is a great hope as a nutraceutical in drug discovery, against CDG, diabetes, obesity, lung disease, and autoimmune diseases and recent findings of anti-tumor activity make it interesting along with its role in drug delivery enhancing techniques. A very unique work done in the present investigation is the collection of data from the ChEMBL database and presenting the targetable proteins on pathogens as well as on humans. It shows Mannose has 50 targets and the majority of them are on human beings. The structure and conformation of certain monosaccharides have a decisive role in receptor pathogen interactions and here we attempt to review the multifaceted roles of Mannose sugar, its targets associated with different diseases, as a natural molecule having many success stories as a drug and future hope for disease management.

Graphical abstract

High lignin-containing nanocelluloses prepared via TEMPO-mediated oxidation and polyethylenimine functionalization for antioxidant and antibacterial applications

Lignin-containing nanocelluloses (LNCs) have attracted tremendous research interest in recent years due to less complex extraction processes and more abundant functionality compared to lignin-free nanocelluloses. On the other hand, traditional defibrillation primarily based on bleached pulp would not be readily applied to lignin-containing pulps due to their complex compositions. This study was focused on LNC extraction from lignin-containing pulp via 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation. Three types of switchgrass pulp with varying composition were prepared using different acid-catalyzed pretreatments. The pulps contained as high as 45.76% lignin but minor/no hemicellulose, corresponding to up to 23.72% lignin removal and 63.75-100% hemicellulose removal. TEMPO-mediated oxidation yielded 52.9-81.9% LNCs from respective pulps. The as-produced LNCs possessed aspect ratios as high as 416.5, and carboxyl contents of 0.442-0.743 mmol g-1 along with ζ-potential of -50.4 to -38.3 mV. The TEMPO-oxidized LNCs were further modified by polyethylenimine (PEI), which endowed the LNCs with positive charges plus antioxidant and antibacterial activities. Specifically, the PEI-modified LNCs almost fully scavenged 2,2'-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS) radicals at 50 mg L-1 and suppressed the growth of Gram-positive Staphylococcus aureus at 250 μg mL-1.

Dual Dynamic Covalently Crosslinked Alginate Hydrogels with Tunable Properties and Multiple Stimuli-Responsiveness

Alginate is a biopolymer that can be crosslinked with calcium ions to fabricate cytocompatible hydrogels. However, using calcium ions to crosslink alginate provides limited properties and functions to alginate hydrogels, restricting their biomedical applications. Here, phenylboronic acid-functionalized polyethyleneimine (PBA-PEI) was developed to introduce two orthogonal dynamic covalent crosslinks in the alginate hydrogels, where PBA-PEI was used to crosslink alginate dialdehyde (ADA) through imine bonds and boronate ester bonds. The grafting degree of PBA in the PEI structure was applied to fine-tune the properties of PBA-PEI/ADA hydrogels, including the rheological property, mechanical strength, swelling behavior, and antibacterial activity. In particular, the highly sensitive boronate ester bonds in the network enabled PBA-PEI/ADA hydrogels to be responsive to several stimuli, such as glucose, fructose, and hydrogen peroxide. Taken together, PBA-PEI/ADA hydrogels with tunable properties and multiple stimuli-responsiveness have been demonstrated as smart biomaterials for advanced biomedical applications.

Polymers showing intrinsic antimicrobial activity

Pathogenic microorganisms are considered to a major threat to human health, impinging on multiple sectors including hospitals, dentistry, food storage and packaging, and water contamination. Due to the increasing levels of antimicrobial resistance shown by pathogens, often caused by long-term abuse or overuse of traditional antimicrobial drugs, new approaches and solutions are necessary. In this area, antimicrobial polymers are a viable solution to combat a variety of pathogens in a number of contexts. Indeed, polymers with intrinsic antimicrobial activities have long been an intriguing research area, in part, due to their widespread natural abundance in materials such as chitin, chitosan, carrageen, pectin, and the fact that they can be tethered to surfaces without losing their antimicrobial activities. In addition, since the discovery of the strong antimicrobial activity of some synthetic polymers, much work has focused on revealing the most effective structural elements that give rise to optimal antimicrobial properties. This has often been synthesis targeted, with the generation of either new polymers or the modification of natural antimicrobial polymers with the addition of antimicrobial enhancing modalities such as quaternary ammonium or guanidinium groups. In this review, the growing number of polymers showing intrinsic antimicrobial properties from the past decade are highlighted in terms of synthesis; often based on post-synthesis modification and their utilization. This includes as surface coatings, for example on medical devices, such as intravascular catheters, orthopaedic implants and contact lenses, or directly as antibacterial agents (specifically as eye drops). Surface functionalisation with inherently antimicrobial polymers is highlighted and has been achieved via various techniques, including surface-bound initiators allowing RAFT or ATRP surface-based polymerization, or via physical immobilization such as by layer-by-layer techniques. This article also covers the mechanistic modes of action of intrinsic antimicrobial polymers against bacteria, viruses, or fungi.

Antifouling and Antibacterial Surfaces Grafted with Sulfur-Containing Copolymers

Antifouling and antibacterial surfaces that can prevent nonspecific biological adhesion are important to support a myriad of biomedical applications. In this study, we have used an innovative photopolymerization technology to develop sulfur-containing polymer-grafted antifouling and antibacterial surfaces. The relationship between the hydrophilic property and the capability to resist protein and macrophage adsorption of the surface copolymer brushes was investigated. The sulfide monomer incorporated into the surface copolymer brushes can be further ionized to carry positive charges and impart antibacterial activity, leading to surfaces with dual antifouling and antibacterial functions. We believe that the reported sulfur-containing polymer brushes can be considered an emerging and important polymer for antifouling and antibacterial applications.

Add Sugar to Chitosan: Mucoadhesion and In Vitro Intestinal Permeability of Mannosylated Chitosan Nanocarriers

Crosslinked chitosan nanocarriers (140–160 nm) entrapping coumarin-6 (λ_ex/em = 455/508 nm) with or without surface mannosylation were synthesized and assessed for cytotoxicity, adherence and cellular uptake in Caco-2 cells, flux across Caco-2 monolayers, and mucoadhesion to porcine mucin. Mannosylated and non-mannosylated nanocarriers demonstrated biocompatibility with slow release of coumarin-6 at pH 6.8 and 7.4 over 24 h. Adherence of the non-mannosylated nanocarriers (50 and 150 µg/mL) to Caco-2 cells was ~10% over 24 h, whereas cellular uptake of 25–30% was noted at 4 h. The mannosylated nanocarriers showed a similar adherence to non-mannosylated nanocarriers after 24 h, but a lower cellular uptake (~20%) at 1 h, comparable uptake at 4 h, and a higher uptake (~25–30%) at 24 h. Overall, the nanocarriers did not affect the integrity of Caco-2 monolayers. Mannosylated nanocarriers elicited higher P_app of 1.6 × 10⁻⁶ cm/s (50 µg/mL) and 1.2 × 10⁻⁶ (150 µg/mL) than the non-mannosylated ones: 9.8 × 10⁻⁷ cm/s (50 µg/mL) and 1.0 × 10⁻⁶ (150 µg/mL) after 2 h. Non-mannosylated chitosan nanocarriers elicited enhanced adhesion to porcine gut mucin via mucin-filled microchannels due to higher cationic charge density. These results underpin the importance of surface chemistry in the biological interactions of nanocarriers, while highlighting the role of surface hydrophilicity in mucopermeation due to mannosylation.

Chain-folding regulated self-assembly, outstanding bactericidal activity and biofilm eradication by biomimetic amphiphilic polymers

Chain-folding regulated hierarchical self-assembly of cationic host defense peptide mimicking amphiphilic polyurethanes exhibit excellent antibacterial activity and biofilm killing.

Multifunctional polyethylene imine hybrids decorated by silica bioactive glass with enhanced mechanical properties, antibacterial, and osteogenesis for bone repair

Inorganic/organic hybrids and bioactive glasses demonstrate promising potential as bone substitute biomaterials. A sol-gel hybrid consisting of silica bioactive glass and biodegradable polymer can combine the high bioactivity of a glass with the toughness of a polymer. In this study, multifunctional hybrids with a combination of organic-inorganic hybrid structure class II consisting of polyethyleneimine (PEI) generation 4 (G4) and bioactive glass with enhanced mechanical properties, mineralization, antibacterial, and osteogenesis activities were synthesized by the sol-gel method. Glycidoxypropyl) trimethoxysilane (GPTMS) with different concentrations was used as a covalent bonding agent between PEI polymer and bioactive glass. The effect of GPTMS content was assessed in the presence and absence of calcium in the hybrid structures in terms of morphology, wettability, mechanical properties, antibacterial activity, cell viability, and in vitro osteogenic differentiation properties. By increasing the amount of GPTMS, the compressive strength increased from 1.95 MPa to 2.34 MPa, which was comparable to human trabecular bone. All the hybrids presented antibacterial activity against Staphylococcus aureus, forming an inhibition zone of 13-16 mm. An increase in cell viability of 82.22% in PSCaG90 was obtained after 1 day of MG-63 cell culture. Alkaline phosphatase expression and mineralization of MG-63 cells increased in the PSCaG90 hybrid in the absence of an osteogenic medium compared to PSG60 and PSG90. The PSCaG90 hybrid indicated considerable in vitro osteogenic capacity in the absence of a differentiation medium, expressing high levels of bone-specific proteins including collagen I (COL1A1), Runt-related transcription factor 2 (RUNX2), osteopontin (OPN), and osteocalcin (OCN), compared to calcium-free hybrids. Overall, our results suggest that the presence of calcium in the PSCaG90 leads to a significant increase in osteogenic differentiation of MG-63 cells even in the absence of differentiation medium, which suggests these hybrid structures with multifunctional properties as promising candidates for bone repair.

Drug-Free Liposomes Containing Mannosylated Ligand for Liver-Targeting: Synthetic Optimization, Liposomal Preparation, and Bioactivity Evaluation

This research was performed to optimize the enzymatic synthesis of mannosylated ligand with which to prepare mannosy-lated liposomes and investigate their bioactivity. Based on single-factor studies, lipase dose, substrate molar ratio (diester lauric diacid-cholesterol to mannose) and temperature were identified as significant parameters, and optimal reaction conditions were determined through response surface methodology (RSM) with central composite design. The optimum operating parameters, 61.23 mg of lipase, a substrate molar ratio of 5.36, and 56.64 °C temperature offered a predicted yield (71.11%) which was consistent with the actual yield (69.08%). Drug-free mannosylated liposomes were prepared film-dispersion. The characterizations of these liposomes showed that mannosylated liposomes were well-dispersible spherical particles with an average particle size of 142.3 nm, the polydispersity index of 0.16, and a zeta potential of -19.8 mV. Pyrogen examination, hemolytic studies and cytotoxicity assays revealed no substantial safety concern for drug-free mannosylated liposomes. Cellular uptake efficiency of mannosylated liposomes by HepG2 cells was significantly higher than that of unmodified liposomes, demonstrating that mannosylated ligands have a positive effect on liver targeting. Overall, mannosylated liposomes could be active drug delivery system for combatting the therapy of hepatic diseases.

Cationic Glycopolymers with Aggregation-Induced Emission for the Killing, Imaging, and Detection of Bacteria

Cationic glycopolymers with structures similar to those of typical poly(ionic liquid)s (PILs) were synthesized via the quaternization reaction of poly(4-vinyl pyridine) with halogen-functionalized d-mannose and tetraphenylethylene units. Such postpolymerization modification provided PILs with aggregation-induced emission effect as well as specific carbohydrate-protein recognition with lectins such as concanavalin A. The interactions between cationic glycopolymers and different microorganisms, including Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli, were used for the killing, imaging, and detection of bacteria. Besides, these sugar-containing PILs showed a relatively low hemolysis rate due to the presence of saccharide units, which may have potential application in the field of biomaterials.

A Hyaluronic Acid Functionalized Self-Nano-Emulsifying Drug Delivery System (SNEDDS) for Enhancement in Ciprofloxacin Targeted Delivery against Intracellular Infection

Ciprofloxacin (CIP), a potent anti-bacterial agent of the fluroquinolone family, shows poor solubility and permeability, thus leading to the development of intracellular pathogens induced multi-drug resistance and biofilms formation. To synergistically improve the biopharmaceutical parameters of CIP, a hyaluronic acid (FDA approved biocompatible polymer) functionalized self-nano emulsifying drug delivery system (HA-CIP-SNEDDS) was designed in the present study. SNEDDS formulations were tested via solubility, droplet size, zeta potential, a polydispersity index, thermodynamic stability, surface morphology, solid-state characterization, drug loading/release, cellular uptake, and biocompatibility. The final (HA-CIP-SNEDDS) formulation exhibited a mean droplet size of 50 nm with the 0.3 poly dispersity index and negative zeta potential (-11.4 mV). HA-based SNEDDS containing CIP showed an improved ability to permeate goat intestinal mucus. After 4 h, CIP-SNEDDS showed a 2-fold and HA-CIP-SNEDDS showed a 4-fold permeation enhancement as compared to the free CIP. Moreover, 80% drug release of HA-CIP-SNEDDS was demonstrated to be superior and sustained for 72 h in comparison to free CIP. However, anti-biofilm activity of HA-CIP-SNEDDS against Salmonella typhi was higher than CIP-SNEDDS and free CIP. HA-CIP-SNEDDS exhibited increased biocompatibility and improved oral pharmacokinetics as compared to free CIP. Taken together, HA-CIP-SNEDDS formulation seems to be a promising agent against Salmonella typhi with a strong targeting potential.

Photothermal-Irradiated Polyethyleneimine-Polypyrrole Nanopigment Film-Coated Polyethylene Fabrics for Infrared-Inspired with Pathogenic Evaluation

Influenza, pneumonia, and pathogenic infection of the respiratory system are boosted in cold environments. Low temperatures also result in vasoconstriction, restraint of blood flow, and decreased oxygen to the heart, and the risk of a heart attack would increase accordingly. The present face mask fabric fails to preserve its air-filtering function as its electrostatic function vanishes once exposed to water. Therefore, its filtering efficacy would be decreased meaningfully, making it nearly impracticable to reuse the disposable face masks. The urgent requirement for photothermal fabrics is also rising. Nanobased polyethyleneimine-polypyrrole nanopigments (NPP NPs) have been developed and have strong near-infrared spectrum absorption and exceptional photothermal convertible performance. Herein, the mask fabric used PE-fiber-constructed membrane (PEFM) was coated by the binding affinity of the cationic polyethyleneimine component of NPP NPs forming NPP NPs-PEFM. To the best of our knowledge, no study has investigated NPP NP-coated mask fabric to perform infrared red (solar or body) photothermal conversion efficacy to provide biocompatible warming, remotely photothermally captured antipathogen, and antivasoconstriction in vivo. This pioneering study showed that the developed NPP NPs-PEFM could be washable, reusable, breathable, biocompatible, and photothermal conversable for active eradication of pathogenic bacteria. Further, it possesses warming preservation and antivasoconstriction.

Preparation of two types of silver-doped fluorescent carbon dots and determination of their antibacterial properties

The preparation and performance of doped antibacterial carbon dots (CDs) have been the research hotspot. In this paper, we report the preparation of two blue light-emitting silver-doped CDs, CD-1 and CD-2, through one- and two-step routes, respectively, by using polyethyleneimine, citric acid, and AgNO₃ as raw materials. Both CDs exhibited excellent and broad-spectrum activity against gram-positive bacteria, gram-negative bacteria, and fungi. We compared the emission wavelength, surface group, particle size, chargeability, and element content of the two CDs through various characterization methods. CD-2 exhibiting longer emission wavelength, larger particle size, and higher silver content displayed higher antibacterial activity against microorganisms than CD-1. On the other hand, CDs exhibited varying antibacterial properties against different microorganisms because of differences in the cell wall structure of gram-positive bacteria (peptidoglycan), gram-negative bacteria (lipopolysaccharides), and fungi (chitin). Based on scanning electron microscopy observations, circular dichroism spectroscopy and agarose gel electrophoresis, we speculate that CDs exert antibacterial activity mainly through membrane disruption and their effect on intracellular DNA and proteins. At the same time, CDs have multicolor imaging capabilities of Staphylococcus aureus. The antibacterial activity and versatility of bioimaging make them more potential antibacterial agents than traditional agents.

One-Step and One-Precursor Hydrothermal Synthesis of Carbon Dots with Superior Antibacterial Activity

Discovering efficient antibacterial materials is crucial in the area of increasing drug resistance. Herein, we synthesized carbon dots (C-dots) with superior antibacterial activity through a simple one-step hydrothermal method. In this method, p-phenylenediamine serves as not only the carbon source but also the origin for the functional group anchored on the obtained C-dots. The antibacterial activity of the obtained C-dots was tested against Staphylococcus aureus and Escherichia coli. The minimum bactericidal concentrations of the synthesized C-dots against S. aureus and E. coli were 2 and 30 μg/mL, respectively, which are lower than that of previously reported C-dots. The antibacterial mechanism was investigated, and the results indicated that a large number of -NH₃⁺ groups on the C-dots' surface enhanced their antibacterial activity. Besides, the C-dots exhibited negligible cytotoxicity.

Nanolayers of Poly(N,N'-Dimethylaminoethyl Methacrylate) with a Star Topology and Their Antibacterial Activity

In this paper, we focus on the synthesis and characterization of novel stable nanolayers made of star methacrylate polymers. The effect of nanolayer modification on its antibacterial properties was also studied. A covalent immobilization of star poly(N,N'-dimethylaminoethyl methacrylate) (PDMAEMA) to benzophenone functionalized glass or silicon supports was carried out via a "grafting to" approach using UV irradiation. To date, star polymer UV immobilization has never been used for this purpose. The thickness of the resulting nanolayers increased from 30 to 120 nm with the molar mass of the immobilized stars. The successful bonding of star PDMAEMA to the supports was confirmed by surface sensitive quantitative spectroscopic methods. Next, amino groups in the polymer layer were quaternized with bromoethane, and the influence of this modification on the antibacterial properties of the obtained materials was analyzed using a selected reference strain of bacteria. The resulting star nanolayer surfaces exhibited higher antimicrobial activity against Bacillus subtilis ATCC 6633 compared to that of the linear PDMAEMA analogues grafted onto a support. These promising results and the knowledge about the influence of the topology and modification of PDMAEMA layers on their properties may help in searching for new materials for antimicrobial applications in medicine.

Glycosylated porphyrin-cucurbituril conjugate for photodynamic inactivation of bacteria and doxorubicin carriage for anticancer drug delivery

Porphyrin derivatives are highly attractive in the construction of multifunctional molecular platforms with interesting properties and applications. In this regard, we report here the use of a multifunctional porphyrin-based molecular platform as a photosensitizer for photodynamic therapy and as a drug carrier. This molecular platform was constructed by conjugating a host molecule, cucurbit[7]uril to a triglycosylated tetraphenyl porphyrin and serves very efficiently as a photosensitizer in the inactivation of both gram-negative (Escherichia coli, E. coli) and gram-positive bacteria (Bacillus subtilis, B. subtilis) and growth inhibition of cancer cells as well as a doxorubicin (DOX) carrier for chemo-photodynamic dual cancer therapy. Another remarkable feature of this photosensitizer is that it shows negligible cytotoxicity in the dark.

Study of the Intrinsic Fluorescence of a Highly Branched Cationic Dendrimer, Poly(Ethyleneimine) (PEI)

Poly(ethyleneimine) (PEI) is a weakly basic, synthetic, polycationic polymer, due to the presence of primary, secondary, and tertiary amino groups. The amino groups are responsible for the variety of applications of PEI (e.g., transfection, bioimaging, solar cell, etc.). Our study presents some new and reproducible methods for the quantification of molecular or mass concentration of highly branched PEI of different molecular weights (800–2000–25,000–750,000 MW PEI). In the course of the direct method, spectrophotometry and fluorometry were applied to determine the absorption and fluorescence of PEI dilution series. An increase in the MW at the same concentration produces a higher count number because of the higher number of amino groups in PEI molecules. The character of increment in fluorescence intensity is essentially different in the case of mass concentrations and molar concentrations. The increment of the fluorescence intensity related to the molar concentration is non-linear. In the case of mass concentration, the slope is linear. Moreover, their fluorescence is enhanced with the decrease in pH values. The spectrophotometry is a reliable method for measuring the quantity of PEI molecules in solution. Our data help in recognizing the detailed properties of PEI in dendrimer research.

Polyethyleneimine and quaternized ammonium polyethyleneimine: the versatile materials for combating bacteria and biofilms

Bacterial infection has become a serious clinical concern due to the emergence of drug-resistance and biofilm formation. Therefore, it is in great demand to develop efficient antimicrobial agents to treat bacterial infection without using antibiotics. Herein, we successfully prepared four quaternized ammonium PEI (QPEI: PEI1200-C2, PEI1200-C4, PEI1200-C6 and PEI1200-C8) using the commercial available PEI1200. Both PEI and four QPEI presented broad-spectrum antimicrobial activity against Gram-negative bacteria (E. coli, and P. aeruginosa) and Gram-positive bacteria (B. amyloliquefaciens and S. aureus), especially PEI1200-C6 showed the strongest antimicrobial activity with good biocompatibility at the MIC concentrations. Besides, PEI1200-C6 showed 4-16-fold better antibacterial effect than PEI1200, and fluorescent microscope imaging demonstrated that both of them could efficiently eradicate biofilms formed by four bacterial strains in vitro. As the accessible broad-spectrum antibacterial agents, PEI1200 and PEI1200-C6 are significant candidates to treat bacterial infections or eradicate biofilms on indwelling medical devices.