Albumin Broadens the Antibacterial Capabilities of Nonantibiotic Small Molecule-Capped Gold Nanoparticles

Albumin-based delivery systems: Recent advances, challenges, and opportunities

Albumin and albumin-based biomaterials have been explored for various applications, including therapeutic delivery, as therapeutic agents, as components of tissue adhesives, and in tissue engineering applications. Albumin has been approved as a nanoparticle containing paclitaxel (Abraxane®), as an albumin-binding peptide (Victoza®), and as a glutaraldehyde-crosslinked tissue adhesive (BioGlue®). Albumin is also approved as a supportive therapy for various conditions, including hypoalbuminemia, sepsis, and acute respiratory distress syndrome (ARDS). However, no other new albumin-based systems in a hydrogel format have been used in the clinic. A review of publicly available clinical trials indicates that no new albumin drug delivery formats are currently in the clinical development pipeline. Although albumin has shown promise as a carrier of therapeutics for various diseases, including diabetes, cancers, and infectious diseases, its potential for treating blood-borne diseases such as HIV and leukemia has not been translated. This review offers a perspective on the use of albumin-based drug delivery systems for a broader range of disease applications, considering the protein properties and a review of the currently approved albumin-based technologies. This review supports ongoing efforts to advance biomedical research and clinical interventions through albumin-based delivery systems.

Metal-Protein Hybrid Materials: Unlocking New Frontiers in Biomedical Applications

Metal-protein hybrid materials represent a novel class of functional materials that exhibit exceptional physicochemical properties and tunable structures, rendering them remarkable applications in diverse fields, including materials engineering, biocatalysis, biosensing, and biomedicine. The design and development of multifunctional and biocompatible metal-protein hybrid materials have been the subject of extensive research and a key aspiration for practical applications in clinical settings. This review provides a comprehensive analysis of the design strategies, intrinsic properties, and biomedical applications of these hybrid materials, with a specific emphasis on their potential in cancer therapy, drug and vaccine delivery, antibacterial treatments, and tissue regeneration. Through rational design, stable metal-protein hybrid materials can be synthesized using straightforward methods, enabling them with therapeutic, delivery, immunomodulatory, and other desired functionalities. Finally, the review outlines the existing limitations and challenges associated with metal-protein hybrid materials and evaluates their potential for clinical translation, providing insights into their practical implementation within biomedical applications.

Defending Ti6Al4V against Biofilm Formation with Albumin Biofunctionalization

Surface biofunctionalization with structurally perturbed albumin, as well as with other plasmatic proteins, inhibits the initial bacterial adhesion and biofilm formation, involved in numerous healthcare-associated infections. In fact, we have reported this protective effect with thermally treated plasmatic proteins, such as albumin and fibrinogen, adsorbed on flat silica surfaces. Here, we show that albumin biofunctionalization also works properly on flat Ti6Al4V substrates, which are widely used to fabricate medical devices. The protective effect is conserved even in biologically relevant fluids, containing other proteins that potentially adsorb onto and/or displace preadsorbed albumin from the biofunctionalized substrates. We further demonstrate that the presence of structurally perturbed albumin on the substrate does not trigger macrophage activation and the release of inflammatory mediators. Consequently, surface biofunctionalization with thermally perturbed albumin is a simple strategy to prepare antibacterial, nonimmunogenic medical devices.

Evaluating the Effects of BSA-Coated Gold Nanorods on Cell Migration Potential and Inflammatory Mediators in Human Dermal Fibroblasts

Albumin-coated gold nanoparticles display potential biomedical applications, including cancer research, infection treatment, and wound healing; however, elucidating their interaction with normal cells remains an area with limited exploration. In this study, gold nanorods (GNR) were prepared and coated with bovine serum albumin (BSA) to produce GNR-BSA. The functionalized nanoparticles were characterized based on their optical absorption spectra, morphology, surface charge, and quantity of attached protein. The interaction between GNR-BSA and BSA with normal cells was investigated using human dermal fibroblasts. The cytotoxicity test indicated cell viability between ~63-95% for GNR-BSA over concentrations from 30.0 to 0.47 μg/mL and ~85-98% for BSA over concentrations from 4.0 to 0.0625 mg/mL. The impact of the GNR-BSA and BSA on cell migration potential and wound healing was assessed using scratch assay, and the modulation of cytokine release was explored by quantifying a panel of cytokines using Multiplex technology. The results indicated that GNR-BSA, at 10 μg/mL, delayed the cell migration and wound healing 24 h post-treatment compared to the BSA or the control group with an average wound closure percentage of 6% and 16% at 6 and 24 h post-treatment, respectively. Multiplex analysis revealed that while GNR-BSA reduced the release of the pro-inflammatory marker IL-12 from the activated fibroblasts 24 h post-treatment, they significantly reduced the release of IL-8 (p < 0.001), and CCL2 (p < 0.01), which are crucial for the inflammation response, cell adhesion, proliferation, migration, and angiogenesis. Although GNR-BSA exhibited relatively high cell viability towards human dermal fibroblasts and promising therapeutic applications, toxicity aspects related to cell motility and migration must be considered.

Antimicrobial activity of metal-based nanoparticles: a mini-review

The resistance of pathogenic microorganisms to antibiotics is one of the main problems of world health. Of particular concern are multidrug-resistant (MDR) bacteria. Infections caused by these microorganisms affect the appearance of acute or chronic diseases. In this regard, modern technologies, such as nanomaterials (NMs), especially promising nanoparticles (NPs), can possess antimicrobial properties or improve the effectiveness and delivery of known antibiotics. Their diversity and characteristics, combined with surface functionalization, enable multivalent interactions with microbial biomolecules. This article presents an overview of the most current research on replacing antibiotics with NPs, including the prospects and risks involved.

Antibacterial Mechanism of d-Cysteine/Polyethylene Glycol-Functionalized Gold Nanoparticles and Their Potential for the Treatment of Bacterial Infections

Bacterial infection has always posed a severe threat to public health. Gold nanoparticles (Au NPs) exhibit exceptional biocompatibility and hold immense potential in biomedical applications. However, their antibacterial effectiveness is currently unsatisfactory. Herein, a chiral antibacterial agent with high stability was prepared by the modification of Au NPs with d-cysteine with the assistance of polyethylene glycol (PEG). The as-synthesized d-cysteine/PEG-Au NPs (D/P-Au NPs) exhibited a stronger (99.5-99.9%) and more stable (at least 14 days) antibacterial performance against Gram-negative (Escherichia coli and Listeria monocytogenes) and Gram-positive (Salmonella enteritidis and Staphylococcus aureus) bacteria, compared with other groups. The analysis of the antibacterial mechanism revealed that the D/P-Au NPs mainly affected the assembly of ribosomes, the biosynthesis of amino acids and proteins, as well as the DNA replication and mismatch repair, ultimately leading to bacterial death, which is significantly different from the mechanism of reactive oxygen species-activated metallic antibacterial NPs. In particular, the D/P-Au NPs were shown to effectively accelerate the healing of S. aureus-infected wounds in mice to a rate comparable to or slightly higher than that of vancomycin. This work provides a novel approach to effectively design chiral antibacterial agents for bacterial infection treatment.

Enhanced adhesive and mechanically robust silicone-based coating with excellent marine anti-fouling and anti-corrosion performances

Poly(dimethylsiloxane) (PDMS) is widely used in marine antifouling coatings due to its low surface energy property. However, certain drawbacks of PDMS coatings such as poor surface adhesion, weak mechanical properties, and inadequate static antifouling performance have hindered its practical applications. Herein, condensation polymerization is utilized to prepare PDMS-based polythiamine ester (PTUBAF) coatings that consist of PDMS, polytetrahydrofuran (PTMG), 2, 3, 5, 6-tetrafluoro-1, 4-benzenedimethanol (TBD) as the main chains and isobornyl acrylate(IBA) as the antifouling group. The surface adhesion to the substrate is enhanced due to the hydrogen bond between the coated carbamate group and the hydroxyl group on the surface of the substrate. Mechanical properties of PTUBAF are significantly improved due to the benzene ring and six-membered ring biphase hard structure. The strong synergistic effect of bactericidal groups and low surface energy surface endows the PTUBAF coating with outstanding antifouling performance. Due to the low surface energy surface, the PTUBAF coatings are also found to possess excellent anti-corrosion. Furthermore, since the PTUBAF coatings exhibit a visible light transmittance of 91 %, they can applied as protective films for smartphones. The proposed method has the potential to boost the production and practical applications of silicone-based coatings.

Strategies to Promote the Journey of Nanoparticles Against Biofilm-Associated Infections

Biofilm-associated infections are one of the most challenging healthcare threats for humans, accounting for 80% of bacterial infections, leading to persistent and chronic infections. The conventional antibiotics still face their dilemma of poor therapeutic effects due to the high tolerance and resistance led by bacterial biofilm barriers. Nanotechnology-based antimicrobials, nanoparticles (NPs), are paid attention extensively and considered as promising alternative. This review focuses on the whole journey of NPs against biofilm-associated infections, and to clarify it clearly, the journey is divided into four processes in sequence as 1) Targeting biofilms, 2) Penetrating biofilm barrier, 3) Attaching to bacterial cells, and 4) Translocating through bacterial cell envelope. Through outlining the compositions and properties of biofilms and bacteria cells, recent advances and present the strategies of each process are comprehensively discussed to combat biofilm-associated infections, as well as the combined strategies against these infections with drug resistance, aiming to guide the rational design and facilitate wide application of NPs in biofilm-associated infections.

Composite Remineralization of Bone-Collagen Matrices by Low-Temperature Ceramics and Serum Albumin: A New Approach to the Creation of Highly Effective Osteoplastic Materials

This study examined the effectiveness of coating demineralized bone matrix (DBM) with amorphous calcium phosphate (DBM + CaP), as well as a composite of DBM, calcium phosphate, and serum albumin (DBM + CaP + BSA). The intact structure of DBM promotes the transformation of amorphous calcium phosphate (CaP) into dicalcium phosphate dihydrate (DCPD) with a characteristic plate shape and particle size of 5-35 µm. The inclusion of BSA in the coating resulted in a better and more uniform distribution of CaP on the surface of DBM trabeculae. MG63 cells showed that both the obtained forms of CaP and its complex with BSA did not exhibit cytotoxicity up to a concentration of 10 mg/mL in vitro. Ectopic (subcutaneous) implantation in rats revealed pronounced biocompatibility, as well as strong osteoconductive, osteoinductive, and osteogenic effects for both DBM + CaP and DBM + CaP + BSA, but more pronounced effects for DBM + CaP + BSA. In addition, for the DBM + CaP + BSA samples, there was a pronounced full physiological intrafibrillar biomineralization and proangiogenic effect with the formation of bone-morrow-like niches, accompanied by pronounced processes of intramedullary hematopoiesis, indicating a powerful osteogenic effect of this composite.

Role of the Human Serum Albumin Protein Corona in the Antimicrobial and Photothermal Activity of Metallic Nanoparticles against Escherichia coli Bacteria

The emergence of antibiotic-resistant bacteria has become a major public health concern, leading to growing interest in alternative antimicrobial agents. The antibacterial activity of metal nanoparticles (NPs) has been extensively studied, showing that they can effectively inhibit the growth of various bacteria, including both Gram-positive and -negative strains. The presence of a protein corona, formed by the adsorption of proteins onto the NP surface in biological fluids, can significantly affect their toxicity. Understanding the effect of the protein corona on the antimicrobial activity of metal NPs is crucial for their effective use as antimicrobial agents. In this study, the antimicrobial activity of noble metal NPs, such as platinum (Pt), silver (Ag), and gold (Au) with and without the human serum albumin (HSA) protein corona against Escherichia coli strains, was investigated. In addition, the plasmonic photothermal effect related to AuNPs, which resulted to be the most biocompatible compared to the other considered metals, was evaluated. The obtained results suggest that the HSA protein corona modulated the antimicrobial activity exerted by the metal NPs against E. coli bacteria. These findings may pave the way for the investigation and development of innovative nanoapproaches to face antibiotic resistance emergence.

Preclinical Evaluation of a Protein-Based Nanoscale Contrast Agent for MR Angiography at an Ultralow Dose

PURPOSE

BSA-biomineralized Gd nanoparticles (Gd@BSA NPs) have been recognized as promising nanoscale MR contrast agents. The aim of this study was to carry out a preclinical evaluation of these NPs in a middle-sized animal model (rabbits).

METHODS

New Zealand white rabbits were treated intravenously with Gd@BSA NPs (0.02 mmol Gd/kg) via a clinically-used high-pressure injector, with commercial Gd-diethylene triamine pentaacetate (Gd-DTPA)-injected group as control. Then MR angiography was performed according to the standard clinical protocol with a 3.0-T MR scanner. The SNR and CNR of the main arteries and branches were monitored. Pharmacokinetics and bioclearance were continuously evaluated in blood, urine, and feces. Gd deposition in vital organs was measured by ICP‒MS. Weight monitoring, HE staining, and blood biochemical analysis were also performed to comprehensively estimate systemic toxicity.

RESULTS

The ultrasmall Gd@BSA NPs (<6 nm) exhibited high stability and T1 relaxivity. Compared to Gd-DTPA, Gd@BSA NPs demonstrated superior vascular system imaging performance at ultralow doses, especially of the cardiac artery and other main branches, and exhibited a significantly higher SNR and CNR. Notably, the Gd@BSA NPs showed a shorter half-life in blood, less retention in organs, and improved biocompatibility.

CONCLUSION

The preclinical evaluations here demonstrated that Gd@BSA NPs are promising and advantageous MR CA candidates that can be used at a low dose with excellent MR imaging performance, thus suggesting its further clinical trials and applications.

Multi-armed antibiotics for Gram-positive bacteria

Antibiotic resistance is a serious threat to public health. Here, we propose a multi-armed chemical scaffold (MACS) for antibiotic screening, which refers to multi-armed molecules (MAMs) consisting of a core unit and three or four arms, neither of which is active for pathogens. Based on a structure-activity relationship study of MAMs, we discover a class of multi-armed antibiotics (MAAs) with a core similar to ethylene (E), carbon atom (C), benzene (B), nitrogen atom (N), and triazine (T) and three or four 4-phenylbenzoic acid (PBA) arms, or a B core and three 4-vinylbenzoic acid (VBA) or 4-ethynylbenzoic acid (EBA) arms. They can selectively interact with Gram-positive bacteria and inhibit cell wall assembly by targeting the lipid carriers of cell wall biosynthesis. MAAs have excellent antibacterial activities against Gram-positive bacteria, including clinical multi-drug-resistant (MDR) isolates. Our study provides a chemical scaffold and identifies eight antibacterial lead compounds for the development of antibiotics.

Hybrid Nanosystems of Antibiotics with Metal Nanoparticles-Novel Antibacterial Agents

The appearance and increasing number of microorganisms resistant to the action of antibiotics is one of the global problems of the 21st century. Already, the duration of therapeutic treatment and mortality from infectious diseases caused by pathogenic microorganisms have increased significantly over the last few decades. Nanoscale inorganic materials (metals and metal oxides) with antimicrobial potential are a promising solution to this problem. Here we discuss possible mechanisms of pathogenic microorganisms' resistance to antibiotics, proposed mechanisms of action of inorganic nanoparticles on bacterial cells, and the possibilities and benefits of their combined use with antibacterial drugs. The prospects of using metal and metal oxide nanoparticles as carriers in targeted delivery systems for antibacterial compositions are also discussed.

Antibacterial Nanomaterials: Mechanisms, Impacts on Antimicrobial Resistance and Design Principles

Antimicrobial resistance (AMR) is one of the biggest threats to the environment and health. AMR rapidly invalidates conventional antibiotics, and antimicrobial nanomaterials have been increasingly explored as alternatives. Interestingly, several antimicrobial nanomaterials show AMR-independent antimicrobial effects without detectable new resistance and have therefore been suggested to prevent AMR evolution. In contrast, some are found to trigger the evolution of AMR. Given these seemingly conflicting findings, a timely discussion of the two faces of antimicrobial nanomaterials is urgently needed. This review systematically compares the killing mechanisms and structure-activity relationships of antibiotics and antimicrobial nanomaterials. We then focus on nano-microbe interactions to elucidate the impacts of molecular initiating events on AMR evolution. Finally, we provide an outlook on future antimicrobial nanomaterials and propose design principles for the prevention of AMR evolution.

The Activity of Vossia cuspidata Polysaccharides-Derived Monometallic CuO, Ag, Au, and Trimetallic CuO-Ag-Au Nanoparticles Against Cancer, Inflammation, and Wound Healing

The biosynthesis of metal nanoparticles using plant extracts is an eco-friendly and inexpensive solution that has strong potential and applications in science and industry. This study aims to synthesize Cu, Ag, and Au monometallic and trimetallic nanoparticles (NPs) using the extracted polysaccharides (PS) of Vossia cuspidata (Roxb.) Griff. leaves. Besides, the anti-cancer, anti-inflammatory, and wound healing potentials of the synthesized NPs were tested. The synthesized NPs were characterized using standard technological methods. We succeeded in green synthesizing CuO, Ag, Au, monometallic, and CuO-Ag-Au trimetallic NPs. The synthesized NPs had weak cytotoxicity at low concentrations (6.5 µg/ml), but the viability of cancer cells was reduced by increasing the concentration, suggesting that the synthesized NPs have potent anti-cancer properties against the cells. The synthesized NPs had 19.44–45.9 μg/ml cytotoxic activity (IC50) against the MCF-7 cell line, 16.50–51.92 μg/ml against A549, and 115.90–165.9 μg/ml for normal lung cells (WI-38). TMNPs were the most effective cytotoxic agents against all the tested cell lines, followed by AuNPs on MCF-7 and CuONPs on A549. The cotton fabric-treated TMNPs and CuONPs exhibited anti-inflammatory properties greater than fabric-treated AgNPs and AuNPs and showed the highest odema inhibition (84.61% and 79.28%, respectively). In the wound healing assay, CuONPs and TMNPs caused the highest percentages of inhibition (87.82% and 61.98%, respectively) for the wound compared to AgNPs and AuNPs. TMNPs and CuONPs were more efficient in restoring the tissue integrity of wounds than AgNPs and AuNPs. Accordingly, we recommend using TMNPs and CuONPs in the wound healing dressings.

Stimuli-Activable Metal-Bearing Nanomaterials and Precise On-Demand Antibacterial Strategies

Bacterial infections remain the leading cause of death worldwide today. The emergence of antibiotic resistance has urged the development of alternative antibacterial technologies to complement or replace traditional antibiotic treatments. In this regard, metal nanomaterials have attracted great attention for their controllable antibacterial functions that are less prone to resistance. This review discusses a particular family of stimuli-activable metal-bearing nanomaterials (denoted as SAMNs) and the associated on-demand antibacterial strategies. The various SAMN-enabled antibacterial strategies stem from basic light and magnet activation, with the addition of bacterial microenvironment responsiveness and/or bacteria-targeting selectivity and therefore offer higher spatiotemporal controllability. The discussion focuses on nanomaterial design principles, antibacterial mechanisms, and antibacterial performance, as well as emerging applications that desire on-demand and selective activation (i.e., medical antibacterial treatments, surface anti-biofilm, water disinfection, and wearable antibacterial materials). The review concludes with the authors' perspectives on the challenges and future directions for developing industrial translatable next-generation antibacterial strategies.

Albumin as a Biomaterial and Therapeutic Agent in Regenerative Medicine

Albumin is a constitutional plasma protein, with well-known biological functions, e.g., a nutrient for stem cells in culture. However, albumin is underutilized as a biomaterial in regenerative medicine. This review summarizes the advanced therapeutic uses of albumin, focusing on novel compositions that take advantage of the excellent regenerative potential of this protein. Albumin coating can be used for enhancing the biocompatibility of various types of implants, such as bone grafts or sutures. Albumin is mainly known as an anti-attachment protein; however, using it on implantable surfaces is just the opposite: it enhances stem cell adhesion and proliferation. The anticoagulant, antimicrobial and anti-inflammatory properties of albumin allow fine-tuning of the biological reaction to implantable tissue-engineering constructs. Another potential use is combining albumin with natural or synthetic materials that results in novel composites suitable for cardiac, neural, hard and soft tissue engineering. Recent advances in materials have made it possible to electrospin the globular albumin protein, opening up new possibilities for albumin-based scaffolds for cell therapy. Several described technologies have already entered the clinical phase, making good use of the excellent biological, but also regulatory, manufacturing and clinical features of serum albumin.

Deploying Gold Nanomaterials in Combating Multi-Drug-Resistant Bacteria

Antibiotic resistance has become a serious threat to human health due to the overuse of antibiotics. Different antibiotics are being developed to treat resistant bacteria, but the development cycle of antibiotics is hard to keep up with the high incidence of antibiotic resistance. Recent advances in antimicrobial nanomaterials have made nanotechnology a powerful solution to this dilemma. Among these nanomaterials, gold nanomaterials have excellent antibacterial efficacy and biosafety, making them alternatives to antibiotics. This review presents strategies that use gold nanomaterials to combat drug-resistant bacteria. We focus on the influence of physicochemical factors such as surface chemistry, size, and shape of gold nanomaterials on their antimicrobial properties and describe the antimicrobial applications of gold nanomaterials in medical devices. Finally, the existing challenges and future directions are discussed.

Nanomaterials-Based Combinatorial Therapy as a Strategy to Combat Antibiotic Resistance

Since the discovery of antibiotics, humanity has been able to cope with the battle against bacterial infections. However, the inappropriate use of antibiotics, the lack of innovation in therapeutic agents, and other factors have allowed the emergence of new bacterial strains resistant to multiple antibiotic treatments, causing a crisis in the health sector. Furthermore, the World Health Organization has listed a series of pathogens (ESKAPE group) that have acquired new and varied resistance to different antibiotics families. Therefore, the scientific community has prioritized designing and developing novel treatments to combat these ESKAPE pathogens and other emergent multidrug-resistant bacteria. One of the solutions is the use of combinatorial therapies. Combinatorial therapies seek to enhance the effects of individual treatments at lower doses, bringing the advantage of being, in most cases, much less harmful to patients. Among the new developments in combinatorial therapies, nanomaterials have gained significant interest. Some of the most promising nanotherapeutics include polymers, inorganic nanoparticles, and antimicrobial peptides due to their bactericidal and nanocarrier properties. Therefore, this review focuses on discussing the state-of-the-art of the most significant advances and concludes with a perspective on the future developments of nanotherapeutic combinatorial treatments that target bacterial infections.

Washable Patches with Gold Nanowires/Textiles in Wearable Sensors for Health Monitoring

Textile-based flexible electronic devices have attracted tremendous attention in wearable sensors due to their excellent skin affinity and conformability. However, the washing process of such devices may damage the electronic components. Here, a textile-based piezoresistive sensor with ultrahigh sensitivity was fabricated through the layered integration of gold nanowire (AuNW)-impregnated cotton fabric and silver ink screen-printed nylon fabric electrodes, sealing with Parafilm. The prepared piezoresistive sensing patch exhibits outstanding performance, including high sensitivity (914.970 kPa^-1, <100 Pa), a fast response time (load: 38 ms, recovery: 34 ms), and a low detection limit (0.49 Pa). More importantly, it can maintain a stable signal output even after 30 000 s of loading-unloading cycles. Furthermore, this sensing patch can efficiently detect breathing, pulse, heart rate, and joint movements during the activities. After five cycles of mechanical washing, the piezoresistive performance keeps 90.3%, demonstrating the high feasibility of this sensor in practical applications. This sensor has a simple fabrication, with good fatigue resistance and durability due to its all-fabric core element. It provides a strategy to address the machine-washing issues in textile electronics. This washable textile sensor is expected to show significant potential in future applications of health monitoring, human-machine interfaces, and artificial skin.

Room-Temperature Harvesting Oxidase-Mimicking Enzymes with Exogenous ROS Generation in One Step

Despite the advantages of low cost, high stability, and activities, a majority of nanozymes rely on strict synthesis conditions and precise size/structure control, hindering the stable, bulk, and high-yield production that is necessary for general use. To facilitate the transition of nanozymes from benchtop to real-world applications, we herein present a one-step approach, which only needs mixing of two broad commercialized reagents at room temperature, to harvest gold nanoparticles-bovine serum albumin (BSA) nanocomposite (BSA-Au) with distinct oxidase-like activity and good stability in a broad range of harsh conditions. Density functional theory (DFT) calculations demonstrate the oxidase-like activity of BSA-Au stemming from thermodynamically and kinetically favored facets for O2 activation. The reactive oxygen species (ROS) generation of BSA-Au contributes to the catalytic activities and further enables water sterilization and antibacterial applications against superbugs. This one-step strategy promises great potential in bulk production of nanozyme for broad application beyond laboratory use.

Fluorescent and Antibacterial Aminobenzeneboronic Acid (ABA)-Modified Gold Nanoclusters for Self-Monitoring Residual Dosage and Smart Wound Care

The replacement of dressings may cause secondary damage to the wounds; thus, the real-time monitoring of the state of wound dressings is crucial for evaluating wound care processes. Herein, we report a smart dressing to self-monitor residue nanomedicine on it during the application. We load aminobenzeneboronic acid (ABA)-modified gold nanoclusters (A-GNCs) on bacterial cellulose (BC) membranes as an antibacterial wound dressing to display the amount of residual nanomedicine (A-GNCs) by in situ colorimetry during the application in remedying multi-drug-resistant (MDR) bacteria-infected wounds. A-GNCs emit bright orange fluorescence under UV light, whereas the BC membrane is transparent at a humidified state on the wounds. Thus, the BC-A-GNCs nanocomposite (BGN) shows decreasing intensity of orange fluorescence with the release of the A-GNCs, indicating the appropriate time points for the replacement of the dressing. The BGN, which can realize accurate self-monitoring in a simple, low-cost, and efficient way, thus holds great promise for broad clinical applications.

Intrinsic Antibacterial and Conductive Hydrogels Based on the Distinct Bactericidal Effect of Polyaniline for Infected Chronic Wound Healing

Most chronic wounds suffer from infections, and their treatment is challenging. The usage of antibiotics may lead to bacterial resistance and adverse side effects. Positively charged substances have shown promise, but their applications are usually limited by certain cytotoxicity or complex synthesis. Doped polyaniline that carries a high density of positive charges would be a promising candidate due to its good biocompatibility and easy availability, but its interaction with bacteria has not been elucidated. Herein, the distinct bactericidal effect of polyaniline against Gram-positive bacteria has been verified. The antibacterial activity may result from the specific interaction with lipoteichoic acid to destroy the Gram-positive bacterial cell wall. Polyaniline and a macromolecular dopant (sulfonated hyaluronic acid) are used to construct a flexible hydrogel with skin-mimic electrical conductivity. The in vivo results demonstrate that electrical stimulation (ES) through this hydrogel is superior to ES via separated electrodes (the ES strategy used clinically) for promoting infected chronic wound healing.

Small Molecule-Capped Gold Nanoclusters for Curing Skin Infections

With the long-term and extensive abuse of antibiotics, bacteria can mutate into multidrug-resistant (MDR) strains, resist the existing antibiotics, and escape the danger of being killed. MDR bacteria-caused skin infections are intractable and chronic, becoming one of the most significant and global public-health issues. Thus, the development of novel antimicrobial materials is urgently needed. Non-antibiotic small molecule-modified gold nanoclusters (AuNCs) have great potential as a substitute for commercial antibiotics. Still, their narrow antibacterial spectrum hinders their wide clinical applications. Herein, we report that 4,6-diamino-2-pyrimidinethiol (DAPT)-modified AuNCs (DAPT-AuNCs) can fight against Gram-negative and Gram-positive bacterial strains as well as their MDR counterparts. By modifying DAPT-AuNCs on nanofibrous films, we develop an antibiotic film as innovative dressings for curing incised wounds, which exhibits excellent therapeutic effects on wounds infected by MDR bacteria. Compared to the narrow-spectral one, the broad-spectral antibacterial activity of the DAPT-AuNCs-modified film is more suitable for preventing and treating skin infections caused by various kinds of unknown bacteria. Moreover, the antibacterial films display excellent biocompatibility, implying the great potential for clinical applications.

Surface engineering strategies of gold nanomaterials and their applications in biomedicine and detection

Gold nanomaterials have potential applications in biosensors and biomedicine due to their controllable synthesis steps, high biocompatibility, low toxicity and easy surface modification. However, there are still various limitations including low water solubility and stability, which greatly affect their applications. In addition, some synthetic methods are very complicated and costly. Therefore, huge efforts have been made to improve their properties. This review mainly introduces the strategies for surface modification of gold nanomaterials, such as amines, biological small molecules and organic small molecules as well as the biological applications of these functionalized AuNPs. We aim to provide effective ideas for better functionalization of gold nanomaterials in the future.

Plasmon-Enhanced Antibacterial Activity of Chiral Gold Nanoparticles and In Vivo Therapeutic Effect

d-cysteine (d-cys) has been demonstrated to possess an extraordinary antibacterial activity because of its unique steric configuration. However, inefficient antibacterial properties seriously hinder its wide applications. Here, cysteine-functionalized gold nanoparticles (d-/l-Au NPs) were prepared by loading d-/l-cysteine on the surface of gold nanoparticles for the effective inhibition of Escherichia coli (E. coli) in vitro and in vivo, and the effects on the intestinal microflora in mice were explored during the treatment of E. coli infection in the gut. We found that the antibacterial activity of d-/l-Au NPs was more than 2-3 times higher than pure d-cysteine, l-cysteine and Au NPs. Compared with l-Au NPs, d-Au NPs showed the stronger antibacterial activity, which was related to its unique steric configuration. Chiral Au NPs showed stronger destructive effects on cell membrane compared to other groups, which further leads to the leakage of the cytoplasm and bacterial cell death. The in vivo antibacterial experiment illustrated that d-Au NPs displayed impressive antibacterial activity in the treatment of E. coli-infected mice comparable to kanamycin, whereas they could not affect the balance of intestinal microflora. This work is of great significance in the development of an effective chiral antibacterial agent.

The Effects of Luminescent CdSe Quantum Dot-Functionalized Antimicrobial Peptides Nanoparticles on Antibacterial Activity and Molecular Mechanism

BACKGROUND

With the development of bacterial resistance, the range of effective antibiotics is increasingly becoming more limited. The effective use of nanoscale antimicrobial peptides (AP) in therapeutic and diagnostic methods is a strategy for new antibiotics.

METHODS

Combining both AP and cadmium selenide (CdSe) into a composite material may result in a reagent with novel properties, such as enhanced antibacterial activity, fluorescence and favorable stability in aqueous solution.

RESULTS

AP-loaded CdSe NPs (AP-CdSe NPs) showed strong antibacterial activity against multidrug-resistant (MDR) Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in vitro and in vivo. Colony-forming unit (CFU) and minimum inhibitory concentration (MIC) assays showed that AP-CdSe NPs have highly effective antibacterial activity. The quantitative analysis of apoptosis by flow cytometry analysis further confirmed that MDR E. coli and S. aureus treated with AP-CdSe NPs had death rates of 98.76% and 99.13%, respectively. Also, AP-CdSe NPs was found to inhibit bacterial activity in an in vivo bacteremia model in mice infected with S. aureus. In addition, the antibacterial mechanism of AP-CdSe NPs was determined by RNA sequencing analysis. Gene ontology (GO) analysis and Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis revealed the molecular mechanism of the antibacterial effect of AP-CdSe NPs. Importantly, histopathology analysis, and hematological toxicity analysis indicated that AP-CdSe NPs had few side effects.

CONCLUSION

These results demonstrate that AP loaded on CdSe NPs had a higher water solubility, bioavailability and antibacterial effect compared with raw AP. This study reports findings that are helpful for the design and development of antibacterial treatment strategies based on AP.

The antibacterial activities of MoS2 nanosheets towards multi-drug resistant bacteria

We demonstrated that molybdenum disulfide (MoS₂) nanosheets can be an excellent solar disinfection agent for multi-drug resistant (MDR) bacteria with disinfection efficiencies >99.9999% in only 30 min. Distinct from other reactive oxygen species (ROS)-dependent photocatalysts, both ROS generation and size decrease contributed to the high antibacterial efficiencies of MoS₂.

Gold Nanoparticles: Can They Be the Next Magic Bullet for Multidrug-Resistant Bacteria?

In 2017 the World Health Organization (WHO) announced a list of the 12 multidrug-resistant (MDR) families of bacteria that pose the greatest threat to human health, and recommended that new measures should be taken to promote the development of new therapies against these superbugs. Few antibiotics have been developed in the last two decades. Part of this slow progression can be attributed to the surge in the resistance acquired by bacteria, which is holding back pharma companies from taking the risk to invest in new antibiotic entities. With limited antibiotic options and an escalating bacterial resistance there is an urgent need to explore alternative ways of meeting this global challenge. The field of medical nanotechnology has emerged as an innovative and a powerful tool for treating some of the most complicated health conditions. Different inorganic nanomaterials including gold, silver, and others have showed potential antibacterial efficacies. Interestingly, gold nanoparticles (AuNPs) have gained specific attention, due to their biocompatibility, ease of surface functionalization, and their optical properties. In this review, we will focus on the latest research, done in the field of antibacterial gold nanoparticles; by discussing the mechanisms of action, antibacterial efficacies, and future implementations of these innovative antibacterial systems.

Emerging photothermal-derived multimodal synergistic therapy in combating bacterial infections

Due to the emerging bacterial resistance and the protection of tenacious biofilms, it is hard for the single antibacterial modality to achieve satisfactory therapeutic effects nowadays. In recent years, photothermal therapy (PTT)-derived multimodal synergistic treatments have received wide attention and exhibited cooperatively enhanced bactericidal activity. PTT features spatiotemporally controllable generation of hyperthermia that could eradicate bacteria without inducing resistance. The synergy of it with other treatments, such as chemotherapy, photo-dynamic/catalytic therapy (PDT/PCT), immunotherapy, and sonodynamic therapy (SDT), could lower the introduced laser density in PTT and avoid undesired overheating injury of normal tissues. Simultaneously, by heat-induced improvement of the bacterial membrane permeability, PTT is conducive for accelerated intracellular permeation of chemotherapeutic drugs as well as reactive oxygen species (ROS) generated by photosensitizers/sonosensitizers, and could promote infiltration of immune cells. Thereby, it could solve the currently existing sterilization deficiencies of other combined therapeutic modes, for example, bacterial resistance for chemotherapy, low drug permeability for PDT/PCT/SDT, adverse immunoreactions for immunotherapy, etc. Admittedly, PTT-derived synergistic treatments are becoming essential in fighting bacterial infection, especially those caused by antibiotic-resistant strains. This review firstly presents the classical and newly reported photothermal agents (PTAs) in brief. Profoundly, through the introduction of delicately designed nanocomposite platforms, we systematically discuss the versatile photothermal-derived multimodal synergistic therapy with the purpose of sterilization application. At the end, challenges to PTT-derived combinational therapy are presented and promising synergistic bactericidal prospects are anticipated.

2D AuPd alloy nanosheets: one-step synthesis as imaging-guided photonic nano-antibiotics

The complicated synthesis and undesirable biocompatibility of nanomaterials hinder the synergistic photothermal/photodynamic therapy for bacterial infections. Herein, we develop a one-step preparation method of 2D AuPd alloy nanosheets as imaging-guided photonic nano-antibiotics. 2D AuPd alloy nanosheets with an extremely small thickness (∼1.5 nm) exhibit prominent photothermal effects (η = 76.6%), excellent ROS generation, strong photoacoustic signals and desirable biocompatibility. AuPd nanosheets can eliminate 100% of representative Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) when irradiated using an 808 nm laser at 1 W cm^-2 for 5 minutes. After being modified with a bacterial targeting peptide, under the guidance of photoacoustic imaging, AuPd nanosheets achieve promising synergistic photothermal/photodynamic therapeutic efficacy in treating Staphylococcus aureus infected mice. This work expands the biomedical application of 2D noble metal nanomaterials to the field of photonic nano-antibiotics.

Gold Nanoclusters for Bacterial Detection and Infection Therapy

Infections caused by antibiotic-resistant bacteria have become one of the most serious global public health crises. Early detection and effective treatment can effectively prevent deterioration and further spreading of the bacterial infections. Therefore, there is an urgent need for time-saving diagnosis as well as therapeutically potent therapy approaches. Development of nanomedicine has provided more choices for detection and therapy of bacterial infections. Ultrasmall gold nanoclusters (Au NCs) are emerging as potential antibacterial agents and have drawn intense attention in the biomedical fields owing to their excellent biocompatibility and unusual physicochemical properties. Recent significant efforts have shown that these versatile Au NCs also have great application potential in the selective detection of bacteria and infection treatment. In this review, we will provide an overview of research progress on the development of versatile Au NCs for bacterial detection and infection treatment, and the mechanisms of action of designed diagnostic and therapeutic agents will be highlighted. Based on these cases, we have briefly discussed the current issues and perspective of Au NCs for bacterial detection and infection treatment applications.