Comparative study of an antimicrobial peptide and a neuropeptide conjugated with gold nanorods for the targeted photothermal killing of bacteria

Eco-Friendly and Low-Cost Synthesis of Transparent Antiviral- and Antibacterial-Coated Films Based on Cu2O and MIL-53(Al)

This research presents the development of an innovative antimicrobial coating consisting of cuprous oxide (Cu2O) integrated with the metal-organic framework MIL-53(Al) through an eco-friendly and low-cost synthesis method that employs glucose as a reducing agent under mild conditions. The microstructural properties of the composite materials were characterized by using X-ray diffraction (XRD) and transmission electron microscopy (TEM). The antibacterial efficacy of the Cu2O-MIL-53(Al) (CuM) composite was assessed against Escherichia coli and Staphylococcus aureus, achieving a reduction efficacy of 99.99% with 5% copper incorporated into the MIL-53(Al) framework within a contact time of 24 h. The incorporation of CuM into a macromolecular host matrix of polyurethane-carboxymethylcellulose (CuM/PUD-CMC), applied as a coating on a low-cost plastic film, produced a transparent film with 87.10% transparency. This coating demonstrated a 99.99% reduction in E. coli and S. aureus populations within a contact time of 24 h. The CuM/PUD-CMC coating demonstrated substantial antiviral efficacy, achieving inactivation rates of 99.35% for Human Coronavirus 229E, 99.40% for Influenza A virus, and 97.76% for Enterovirus 71 within a contact time of 5 min. The CuM nanoparticles exhibited low toxicity toward zebrafish while effectively eradicating bacteria and inactivating viruses. The proposed low-cost material and coating method demonstrate significant potential as a broad-spectrum antimicrobial and antiviral agent, highlighting its suitability for various applications in biomedical and healthcare formulations.

Using gold-based nanomaterials for fighting pathogenic bacteria: from detection to therapy

Owing to the unique quantum size effect and surface effect, gold-based nanomaterials (GNMs) are promising for pathogen detection and broad-spectrum antimicrobial activity. This review summarizes recent research on GNMs as sensors for detecting pathogens and as tools for their elimination. Firstly, the need for pathogen detection is briefly introduced with an overview of the physicochemical properties of gold nanomaterials. And then strategies for the application of GNMs in pathogen detection are discussed. Colorimetric, fluorescence, surface-enhanced Raman scattering (SERS) techniques, dark-field microscopy detection and electrochemical methods can enable efficient, sensitive, and specific pathogen detection. The third section describes the antimicrobial applications of GNMs. They can be used for antimicrobial agent delivery and photothermal conversion and can act synergistically with photosensitizers to achieve the precise killing of pathogens. In addition, GNMs are promising for integrated pathogen detection and treatment; for example, combinations of colorimetric or SERS detection with photothermal sterilization have been demonstrated. Finally, future outlooks for the applications of GNMs in pathogen detection and treatment are summarized.

Gold Nanoparticles and Antimicrobial Peptides: A Novel Combination

This article examines the diverse conjugation forms of AMP‐AuNP nanostructures that arise from the amalgamation of antimicrobial peptides (AMPs) and gold nanoparticles (AuNPs), as well as their prospective utility in the field of biomedicine. AMPs are a class of naturally occurring microbicidal compounds that are recognized for their wide range of inhibitory effects and distinctive modes of operation. The utilization of AuNPs in diverse biomedical applications is facilitated through the application of nanotechnology. AMP‐AuNP nanostructures exhibit diverse features through the utilization of molecular linkage techniques. The aforementioned qualities encompass the ability to expedite the process of wound healing, facilitate precise targeting through the incorporation of DNA aptamers, serve as a means for bacterial imaging, enable the use of photothermal therapy, and contribute to the advancement of prospective treatments for fungal infections. The utilization of these synthesized antimicrobial gold nanostructures in many biomedical applications holds significant promise for advancing treatments and enhancing disease management.

Nanoparticle-Based Strategies for Managing Biofilm Infections in Wounds: A Comprehensive Review

Chronic wounds containing opportunistic bacterial pathogens are a growing problem, as they are the primary cause of morbidity and mortality in developing and developed nations. Bacteria can adhere to almost every surface, forming architecturally complex communities called biofilms that are tolerant to an individual's immune response and traditional treatments. Wound dressings are a primary source and potential treatment avenue for biofilm infections, and research has recently focused on using nanoparticles with antimicrobial activity for infection control. This Review categorizes nanoparticle-based approaches into four main types, each leveraging unique mechanisms against biofilms. Metallic nanoparticles, such as silver and copper, show promising data due to their ability to disrupt bacterial cell membranes and induce oxidative stress, although their effectiveness can vary based on particle size and composition. Phototherapy-based nanoparticles, utilizing either photodynamic or photothermal therapy, offer targeted microbial destruction by generating reactive oxygen species or localized heat, respectively. However, their efficacy depends on the presence of light and oxygen, potentially limiting their use in deeper or more shielded biofilms. Nanoparticles designed to disrupt extracellular polymeric substances directly target the biofilm structure, enhancing the penetration and efficacy of antimicrobial agents. Lastly, nanoparticles that induce biofilm dispersion represent a novel strategy, aiming to weaken the biofilm's defense and restore susceptibility to antimicrobials. While each method has its advantages, the selection of an appropriate nanoparticle-based treatment depends on the specific requirements of the wound environment and the type of biofilm involved. The integration of these nanoparticles into wound dressings not only promises enhanced treatment outcomes but also offers a reduction in the overall use of antibiotics, aligning with the urgent need for innovative solutions in the fight against antibiotic-tolerant infections. The overarching objective of employing these diverse nanoparticle strategies is to replace antibiotics or substantially reduce their required dosages, providing promising avenues for biofilm infection management.

Trends in Photothermal Nanostructures for Antimicrobial Applications

The rapid development of antimicrobial resistance due to broad antibiotic utilisation in the healthcare and food industries and the non-availability of novel antibiotics represents one of the most critical public health issues worldwide. Current advances in nanotechnology allow new materials to address drug-resistant bacterial infections in specific, focused, and biologically safe ways. The unique physicochemical properties, biocompatibility, and wide range of adaptability of nanomaterials that exhibit photothermal capability can be employed to develop the next generation of photothermally induced controllable hyperthermia as antibacterial nanoplatforms. Here, we review the current state of the art in different functional classes of photothermal antibacterial nanomaterials and strategies to optimise antimicrobial efficiency. The recent achievements and trends in developing photothermally active nanostructures, including plasmonic metals, semiconductors, and carbon-based and organic photothermal polymers, and antibacterial mechanisms of action, including anti-multidrug-resistant bacteria and biofilm removal, will be discussed. Insights into the mechanisms of the photothermal effect and various factors influencing photothermal antimicrobial performance, emphasising the structure-performance relationship, are discussed. We will examine the photothermal agents' functionalisation for specific bacteria, the effects of the near-infrared light irradiation spectrum, and active photothermal materials for multimodal synergistic-based therapies to minimise side effects and maintain low costs. The most relevant applications are presented, such as antibiofilm formation, biofilm penetration or ablation, and nanomaterial-based infected wound therapy. Practical antibacterial applications employing photothermal antimicrobial agents, alone or in synergistic combination with other nanomaterials, are considered. Existing challenges and limitations in photothermal antimicrobial therapy and future perspectives are presented from the structural, functional, safety, and clinical potential points of view.

Antimicrobial peptide functionalized gold nanorods combining near-infrared photothermal therapy for effective wound healing

Photothermal therapy using laser activated gold nanorods (AuNRs) is a strategy for treatment of bacterial infections. Nevertheless, it also exerts cytotoxicity against human cells which leads to adverse effects in healthy human tissues and limits the applicable dose. Functionalization of AuNRs with a selective antimicrobial peptide (AMP) with higher selectivity for bacteria over human cells is a promising strategy for increasing the selectivity of the AuNRs for bacteria, hence increasing their cellular uptake by the bacteria in order to achieve stronger antimicrobial effects with lower doses of AuNRs without damaging the human cells. In this study, the surface of AuNRs was functionalized with a short AMP named C-At5 and the efficiency of the peptide functionalized AuNRs in killing gram-positive and gram-negative bacteria was evaluated in vitro as well as their potential for facilitating wound healing in a mouse model of wound infection with and without application of laser. The peptide-conjugated AuNRs exhibited higher antibacterial activity in vitro compared to the plain AuNRs both in the presence and absence of laser irradiation. Furthermore, AuNR@C-At5 had very low toxicity against human skin fibroblasts and human red blood cells indicating their higher biocompatibility compared to the plain AuNRs. Treatment of wounded mice with AuNR@C-At5 accelerated the wound healing process which was further enhanced by applying laser. The system developed in this study has great potential for customization for specific antimicrobial or antifungal therapy via conjugation of different types of AMPs with higher selectivity and can therefore serve as a guide for any future attempts in this regard.

Microbial resistance to nanotechnologies: An important but understudied consideration using antimicrobial nanotechnologies in orthopaedic implants

Microbial resistance to current antibiotics therapies is a major cause of implant failure and adverse clinical outcomes in orthopaedic surgery. Recent developments in advanced antimicrobial nanotechnologies provide numerous opportunities to effective remove resistant bacteria and prevent resistance from occurring through unique mechanisms. With tunable physicochemical properties, nanomaterials can be designed to be bactericidal, antifouling, immunomodulating, and capable of delivering antibacterial compounds to the infection region with spatiotemporal accuracy. Despite its substantial advancement, an important, but under-explored area, is potential microbial resistance to nanomaterials and how this can impact the clinical use of antimicrobial nanotechnologies. This review aims to provide a better understanding of nanomaterial-associated microbial resistance to accelerate bench-to-bedside translations of emerging nanotechnologies for effective control of implant associated infections.

Neuropeptide-Functionalized Gold Nanorod Enhanced Cellular Uptake and Improved In Vitro Photothermal Killing in LRP1-Positive Glioma Cells

The therapeutic modalities for glioblastoma multiforme fail badly due to the limitations of poor penetration through the blood–brain barrier and the lack of tumor targeting. In this study, we synthesized a neuropeptide (ANGIOPEP-2)-functionalized gold nanorod (GNR-ANGI-2) and systemically evaluated the cellular uptake and photothermal effects enhanced by the neuropeptide functionalization of the gold nanorod under laser or sham exposure. The expression of LRP1, the specific ligand for ANGIOPEP-2, was the highest in C6 cells among five studied glioma cell lines. The cellular internalization studies showed higher uptake of gold nanorods functionalized with ANGIOPEP-2 than of those functionalized with scrambled ANGIOPEP-2. The in vitro photothermal studies of C6 cells treated with GNR-ANGI-2 and laser showed a higher rate of apoptosis at early and late stages than cells treated with GNR-ANGI-2 without laser. Correspondingly, in vitro ROS evaluation showed a higher intensity of ROS production in cells treated with GNR-ANGI-2 under laser irradiation. The Western blotting results indicated that GNR-ANGI-2 with laser exposure activated the caspase pathway of apoptosis, and GNR-ANGI-2 with sham exposure induced autophagy in C6 cells. The current study provides in-depth knowledge on the effective time point for maximum cellular uptake of GNR-ANGI-2 to achieve a better anti-glioma effect. Moreover, by exploring the molecular mechanism of cell death with GNR-ANGI-2-mediated photothermal therapy, we could modify the nanoshuttle with multimodal targets to achieve more efficient anti-glioma therapy in the future.

Advances in Nanostructures for Antimicrobial Therapy

Microbial infections caused by a variety of drug-resistant microorganisms are more common, but there are fewer and fewer approved new antimicrobial chemotherapeutics for systemic administration capable of acting against these resistant infectious pathogens. Formulation innovations of existing drugs are gaining prominence, while the application of nanotechnologies is a useful alternative for improving/increasing the effect of existing antimicrobial drugs. Nanomaterials represent one of the possible strategies to address this unfortunate situation. This review aims to summarize the most current results of nanoformulations of antibiotics and antibacterial active nanomaterials. Nanoformulations of antimicrobial peptides, synergistic combinations of antimicrobial-active agents with nitric oxide donors or combinations of small organic molecules or polymers with metals, metal oxides or metalloids are discussed as well. The mechanisms of actions of selected nanoformulations, including systems with magnetic, photothermal or photodynamic effects, are briefly described.