Nanoparticle-mediated stimulus-responsive antibacterial therapy

Design and optimization of ε-poly-l-lysine with specific functions for diverse applications

ε-Poly-l-lysine (ε-PL) is a natural homo-poly(amino acid) which can be produced by microorganisms. With the advantages in broad-spectrum antimicrobial activity, biodegradability, and biocompatibility, ε-PL has been widely used as a preservative in the food industry. Different molecular architectures endow ε-PL and ε-PL-based materials with versatile applications. However, the microbial synthesis of ε-PL is currently limited by low efficiencies in genetic engineering and molecular architecture modification. This review presents recent advances in ε-PL production and molecular architecture modification of microbial ε-PL, with a focus on the current challenges and solutions for the improvement of the productivity and diversity of ε-PL. In addition, we highlight recent examples where ε-PL has been applied to expand the versability of edible films and nanoparticles in various applications. Commercial production and the challenges and future research directions in ε-PL biosynthesis are also discussed. Currently, although the main use of ε-PL is as a food preservative, ε-PL and ε-PL-based polymers have shown excellent application potential in biomedical fields. With the development of synthetic biology, the design and synthesis of ε-PL with a customized molecular architecture are possible in the near future. ε-PL-based polymers with specific functions will be a new trend in biopolymer manufacturing.

Nanozyme-Engineered Hydrogels for Anti-Inflammation and Skin Regeneration

Inflammatory skin disorders can cause chronic scarring and functional impairments, posing a significant burden on patients and the healthcare system. Conventional therapies, such as corticosteroids and nonsteroidal anti-inflammatory drugs, are limited in efficacy and associated with adverse effects. Recently, nanozyme (NZ)-based hydrogels have shown great promise in addressing these challenges. NZ-based hydrogels possess unique therapeutic abilities by combining the therapeutic benefits of redox nanomaterials with enzymatic activity and the water-retaining capacity of hydrogels. The multifaceted therapeutic effects of these hydrogels include scavenging reactive oxygen species and other inflammatory mediators modulating immune responses toward a pro-regenerative environment and enhancing regenerative potential by triggering cell migration and differentiation. This review highlights the current state of the art in NZ-engineered hydrogels (NZ@hydrogels) for anti-inflammatory and skin regeneration applications. It also discusses the underlying chemo-mechano-biological mechanisms behind their effectiveness. Additionally, the challenges and future directions in this ground, particularly their clinical translation, are addressed. The insights provided in this review can aid in the design and engineering of novel NZ-based hydrogels, offering new possibilities for targeted and personalized skin-care therapies.

Stimuli-Actuated Turn-On Theranostic Nanoplatforms for Imaging-Guided Antibacterial Treatment

Antibacterial theranostic nanoplatforms, which integrate diagnostic and therapeutic properties, exhibit gigantic application prospects in precision medicine. However, traditional theranostic nanoplatforms usually present an always-on signal output, which leads to poor specificity or selectivity in the treatment of bacterial infections. To address this challenge, stimuli-actuated turn-on nanoplatforms are developed for simultaneous activation of diagnostic signals (e.g., fluorescent, photoacoustic, magnetic signals) and initiation of antibacterial treatment. Specifically, by combining the infection microenvironment-responsive activation of visual signals and antibacterial activity, these theranostic nanoplatforms exert both higher accurate diagnosis rates and more effective treatment effects. In this review, the imaging and treatment strategies that are commonly used in the clinic are first briefly introduced. Next, the recent progress of stimuli-actuated turn-on theranostic nanoplatforms for treating bacterial infectious diseases is summarized in detail. Finally, current bottlenecks and future opportunities of antibacterial theranostic nanoplatforms are also outlined and discussed.

Precise antibacterial therapeutics based on stimuli-responsive nanomaterials

Bacterial infection refers to the process in which bacteria invade, grow, reproduce, and interact with the body, ultimately causing a series of pathological changes. Nowadays, bacterial infection remains a significant public health issue, posing a huge threat to human health and a serious financial burden. In the post-antibiotic era, traditional antibiotics are prone to inducing bacterial resistance and difficulty in removing bacterial biofilm. In recent years, antibacterial therapy based on nanomaterials has developed rapidly. Compared with traditional antibiotics, nanomaterials effectively remove bacterial biofilms and rarely result in bacterial resistance. However, due to nanomaterials' strong permeability and effectiveness, they will easily cause cytotoxicity when they are not controlled. In addition, the antibacterial effect of non-responsive nanomaterials cannot be perfectly exerted since the drug release property or other antibacterial effects of these nano-materials are not be positively correlated with the intensity of bacterial infection. Stimuli-responsive antibacterial nanomaterials are a more advanced and intelligent class of nano drugs, which are controlled by exogenous stimuli and microenvironmental stimuli to change the dosage and intensity of treatment. The excellent spatiotemporal controllability enables stimuli-responsive nanomaterials to treat bacterial infections precisely. In this review, we first elaborate on the design principles of various stimuli-responsive antibacterial nanomaterials. Then, we analyze and summarizes the antibacterial properties, advantages and shortcomings of different applied anti-bacterial strategies based on stimuli-responsive nanomaterials. Finally, we propose the challenges of employing stimuli-responsive nanomaterials and corresponding potential solutions.

Silver nanoparticles-decorated extracellular matrix graft: fabrication and tendon reconstruction performance

BACKGROUND

The reconstruction of tendons with large defects requires grafts with high mechanical strength and is often hindered by complications such as infection and adhesion. Hence, grafts combining the advantages of mechanical resilience and antibacterial/antiadhesion activity are highly sought after.

METHODS

The silver nanoparticles (GA-Ag NPs) synthesized from gallic acid and silver nitrate were attached to a decellularized extracellular matrix (Decellularized Tendon crosslinking GA-AgNPs, DT-Ag). We examined the histological structure, mechanical property, morphology, Zeta potential, cytotoxicity, antibacterial properties, antioxidant and anti-inflammatory properties, and ability of the DT-Ag to treat tendon defects in animals.

RESULTS

Approximately 108.57 ± 0.94 μg GA-Ag NPs loaded per 50 mg DT, the cross-linked part of GA-Ag NPs was 65.47 ± 0.57%, which provided DT-Ag with long-lasting antibacterial activity. Meanwhile, GA endowed DT-Ag with good antioxidant and anti-inflammatory activities. Additionally, The DT-Ag facilitated M2 macrophage polarization, and suppressed fibrin deposition by hindering fibroblast adhesion. Mormore, the main advantages of DT-Ag, namely its long-lasting antibacterial activity (tested using Escherichia coli and Staphylococcus aureus as models) and the ability to prevent tissue adhesion were confirmed in vivo.

CONCLUSION

The fabricated multifunctional tendon graft was highly hydrophilic, biocompatible, and mechanically resilient, and concluded to be well suited for dealing with the main complications of surgical tendon reconstruction and has bright application prospects.

Collagen-Hyaluronic Acid Composite Hydrogels with Applications for Chronic Diabetic Wound Repair

Chronic diabetic wounds have become a major healthcare challenge worldwide. Improper treatment may lead to serious complications. Current treatment methods including biological and physical methods and skin grafting have limitations and disadvantages, such as poor efficacy, inconvenience of use, and high cost. Therefore, developing a more effective and feasible treatment is of great significance for the repair of chronic diabetic wounds. Hydrogels can be designed to serve multiple functions to promote the repair of chronic diabetic wounds. Furthermore, 3D bioprinting enables hydrogel customization to fit chronic diabetic wounds, thus facilitating the healing process. This paper reports a study of 3D printing of a collagen-hyaluronic acid composite hydrogels with application for chronic diabetic wound repair. In situ printed hydrogels were developed by a macromolecular crosslinking network using methacrylated recombinant human collagen (RHCMA) and methacrylated hyaluronic acid (HAMA), both of which can respond to ultraviolet (UV) irradiation. The hydrogels were also loaded with silver nanoclusters (AgNCs) with ultra-small-size nanoparticles, which have the advantages of deep penetration ability and broad-spectrum high-efficiency antibacterial properties. The results of this study show that the developed RHCMA, HAMA, and AgNCs (RHAg) composite hydrogels present good UV responsiveness, porosity, mechanical properties, printability, and biocompatibility, all of which are beneficial to wound healing. The results of this study further show that the developed RHAg hydrogels not only effectively inhibited Staphylococcus aureus and Pseudomonas aeruginosa but also promoted the proliferation and migration of fibroblasts in vitro and tissue regeneration and collagen deposition in vivo, thus producing a desirable wound repair effect and can be used as an effective functional biomaterial to promote chronic diabetic wound repair.

Promotion of ICD via Nanotechnology

Immunotherapy represents the most promising treatment strategy for cancer, but suffers from compromised therapeutic efficiency due to low immune activity of tumor cells and an immunosuppressive microenvironment, which significantly hampers the clinical translations of this treatment strategy. To promote immunotherapy with desired therapeutic efficiency, immunogenic cell death (ICD), a particular type of death capable of reshaping body's antitumor immune activity, has drawn considerable attention due to the potential to stimulate a potent immune response. Still, the potential of ICD effect remains unsatisfactory because of the intricate tumor microenvironment and multiple drawbacks of the used inducing agents. ICD has been thoroughly reviewed so far with a general classification of ICD as a kind of immunotherapy strategy and repeated discussion of the related mechanism. However, there are no published reviews, to the authors' knowledge, providing a systematic summarization on the enhancement of ICD via nanotechnology. For this purpose, this review first discusses the four stages of ICD according to the development mechanisms, followed by a comprehensive description on the use of nanotechnology to enhance ICD in the corresponding four stages. The challenges of ICD inducers and possible solutions are finally summarized for future ICD-based enhanced immunotherapy.

Piezodynamic Eradication of Both Gram-Positive and Gram-Negative Bacteria by Using a Nanoparticle Embedded Polymeric Membrane

Nowadays, bacterial infection is regarded as a serious threat to humankind, which needs to be taken care of. The emergence of antibiotic resistance and multidrug resistance (MDR) is rendering this situation more troublesome. However, several alternative treatment regimens have aided such diseases quite well in the recent past, among which dynamic antibacterial therapies combat this situation quite well. Among various dynamic therapies, piezodynamic therapy is a very recent avenue, in which mechanical stimuli have been exploited to treat bacterial infections. Herein, piezo-active bismuth ferrite-loaded poly(vinylidene fluoride-co-hexafluoropropylene) polymer has been utilized to eradicate gram-positive bacteria (E. faecalis) and gram-negative bacteria (E. coli). The sample has been designed in a free-standing membrane form, which, under soft ultrasound (~10 kHz), generates reactive radicals to ablate bacteria. Initially, the structure and morphology of the membrane have been substantiated by using X-ray diffraction and scanning electron microscopy methods; besides, Fourier transform infrared spectrum of the sample depicts a tremendously high value of polarizability and further confirms the piezo-activity of the membrane. More than 99% of E. coli and E. faecalis have been successfully eradicated within 30 min of ultrasound. Moreover, the solid-state structure and hydrophobic nature of the membrane help us to reuse it in a cyclic manner, which is possibly reported herein for the very first time. This novel membrane could be deployed in healthcare systems and pigment industries and could be exploited as a self-cleaning material.

Advances in Nanotechnology for Biofilm Inhibition

Biofilm-associated infections have emerged as a significant public health challenge due to their persistent nature and increased resistance to conventional treatment methods. The indiscriminate usage of antibiotics has made us susceptible to a range of multidrug-resistant pathogens. These pathogens show reduced susceptibility to antibiotics and increased intracellular survival. However, current methods for treating biofilms, such as smart materials and targeted drug delivery systems, have not been found effective in preventing biofilm formation. To address this challenge, nanotechnology has provided innovative solutions for preventing and treating biofilm formation by clinically relevant pathogens. Recent advances in nanotechnological strategies, including metallic nanoparticles, functionalized metallic nanoparticles, dendrimers, polymeric nanoparticles, cyclodextrin-based delivery, solid lipid nanoparticles, polymer drug conjugates, and liposomes, may provide valuable technological solutions against infectious diseases. Therefore, it is imperative to conduct a comprehensive review to summarize the recent advancements and limitations of advanced nanotechnologies. The present Review encompasses a summary of infectious agents, the mechanisms that lead to biofilm formation, and the impact of pathogens on human health. In a nutshell, this Review offers a comprehensive survey of the advanced nanotechnological solutions for managing infections. A detailed presentation has been made as to how these strategies may improve biofilm control and prevent infections. The key objective of this Review is to summarize the mechanisms, applications, and prospects of advanced nanotechnologies to provide a better understanding of their impact on biofilm formation by clinically relevant pathogens.

Nanomaterials as multimodal photothermal agents (PTAs) against 'Superbugs'

Superbugs, also known as multidrug-resistant bacteria, have become a lethal and persistent threat due to their unresponsiveness toward conventional antibiotics. The main reason for this is that superbugs can rapidly mutate and restrict any foreign drug/molecule in their vicinity. Herein, nanomaterial-mediated therapies have set their path and shown burgeoning efficiency toward the ablation of superbugs. Notably, treatment modalities like photothermal therapy (PTT) have shown prominence in killing multidrug-resistant bacteria with their ability to generate local heat shock-mediated hyperthermia in such species. However, photothermal treatment has some serious limitations, such as high cost, complexity, and even toxicity to some extent. Hence, it is important to resolve such shortcomings of PTTs as they provide substantial tissue penetration. This is why multimodal PTTs have emerged and taken over this domain of research for the past few years. In this work, we have summarized and critically reviewed such exceptional works of recent times and provided a perspective to enhance their efficiencies. Profoundly, we discuss the design rationales of some novel photothermal agents (PTAs) and shed light on their mechanisms. Finally, challenges for PTT-derived multimodal therapy are presented, and capable synergistic bactericidal prospects are anticipated.