Silver-incorporating peptide and protein supramolecular nanomaterials for biomedical applications

Nano-Micron Combined Hydrogel Microspheres: Novel Answer for Minimal Invasive Biomedical Applications

Hydrogels, key in biomedical research for their hydrophilicity and versatility, have evolved with hydrogel microspheres (HMs) of micron-scale dimensions, enhancing their role in minimally invasive therapeutic delivery, tissue repair, and regeneration. The recent emergence of nanomaterials has ushered in a revolutionary transformation in the biomedical field, which demonstrates tremendous potential in targeted therapies, biological imaging, and disease diagnostics. Consequently, the integration of advanced nanotechnology promises to trigger a new revolution in the realm of hydrogels. HMs loaded with nanomaterials combine the advantages of both hydrogels and nanomaterials, which enables multifaceted functionalities such as efficient drug delivery, sustained release, targeted therapy, biological lubrication, biochemical detection, medical imaging, biosensing monitoring, and micro-robotics. Here, this review comprehensively expounds upon commonly used nanomaterials and their classifications. Then, it provides comprehensive insights into the raw materials and preparation methods of HMs. Besides, the common strategies employed to achieve nano-micron combinations are summarized, and the latest applications of these advanced nano-micron combined HMs in the biomedical field are elucidated. Finally, valuable insights into the future design and development of nano-micron combined HMs are provided.

Recent Progress in Azobenzene-Based Supramolecular Materials and Applications

Azobenzene-containing small molecules and polymers are functional photoswitchable molecules to form supramolecular nanomaterials for various applications. Recently, supramolecular nanomaterials have received enormous attention in material science because of their simple bottom-up synthesis approach, understandable mechanisms and structural features, and batch-to-batch reproducibility. Azobenzene is a light-responsive functional moiety in the molecular design of small molecules and polymers and is used to switch the photophysical properties of supramolecular nanomaterials. Herein, we review the latest literature on supramolecular nano- and micro-materials formed from azobenzene-containing small molecules and polymers through the combinatorial effect of weak molecular interactions. Different classes including complex coacervates, host-guest systems, co-assembled, and self-assembled supramolecular materials, where azobenzene is an essential moiety in small molecules, and photophysical properties are discussed. Afterward, azobenzene-containing polymers-based supramolecular photoresponsive materials formed through the host-guest approach, polymerization-induced self-assembly, and post-polymerization assembly techniques are highlighted. In addition to this, the applications of photoswitchable supramolecular materials in pH sensing, and CO2 capture are presented. In the end, the conclusion and future perspective of azobenzene-based supramolecular materials for molecular assembly design, and applications are given.

Biodegradable Piezoelectric Polymers: Recent Advancements in Materials and Applications

Recent materials, microfabrication, and biotechnology improvements have introduced numerous exciting bioelectronic devices based on piezoelectric materials. There is an intriguing evolution from conventional unrecyclable materials to biodegradable, green, and biocompatible functional materials. As a fundamental electromechanical coupling material in numerous applications, novel piezoelectric materials with a feature of degradability and desired electrical and mechanical properties are being developed for future wearable and implantable bioelectronics. These bioelectronics can be easily integrated with biological systems for applications, including sensing physiological signals, diagnosing medical problems, opening the blood-brain barrier, and stimulating healing or tissue growth. Therefore, the generation of piezoelectricity from natural and synthetic bioresorbable polymers has drawn great attention in the research field. Herein, the significant and recent advancements in biodegradable piezoelectric materials, including natural and synthetic polymers, their principles, advanced applications, and challenges for medical uses, are reviewed thoroughly. The degradation methods of these piezoelectric materials through in vitro and in vivo studies are also investigated. These improvements in biodegradable piezoelectric materials and microsystems could enable new applications in the biomedical field. In the end, potential research opportunities regarding the practical applications are pointed out that might be significant for new materials research.

Current perspectives of metal-based nanomaterials as photocatalytic antimicrobial agents and their therapeutic modes of action: A review

Efforts to restrict the emergence and progression of multidrug-resistant bacterial strains should heavily involve the scientific community, including government bodies, researchers, and industries, in developing new and effective photocatalytic antimicrobial agents. Such changes warrant the modernization and upscaling of materials synthesis laboratories to support and expedite the mass production of materials at the industrial scale for the benefit of humankind and the environment. Despite the massive volume of publications reporting the potential usage of different types of metal-based nanomaterials as antimicrobial agents, reviews uncovering the similarities and differences among the various products remain lacking. This review details the basic and unique properties of metal-based nanoparticles, their use as photocatalytic antimicrobial agents, and their therapeutic modes of action. It shall be noted that compared to traditional antibiotics, the mode of action of photocatalytic metal-based nanomaterials for killing microorganisms are completely different, despite displaying promising performance against antibiotic-resistant bacteria. Besides, this review uncovers the differences in the mode of actions of metal oxide nanoparticles against different types of bacteria, as well as towards viruses. Last but not least, this review comprehensively describes previous published clinical trials and medical usages involving contemporary photocatalytic antimicrobial agents.

Unveiling the Role of Capping Groups in Naphthalene N-Capped Dehydrodipeptide Hydrogels

Self-assembled peptide-based hydrogels are archetypical nanostructured materials with a plethora of foreseeable applications in nanomedicine and as biomaterials. N-protected di- and tri-peptides are effective minimalist (molecular) hydrogelators. Independent variation of the capping group, peptide sequence and side chain modifications allows a wide chemical space to be explored and hydrogel properties to be tuned. In this work, we report the synthesis of a focused library of dehydrodipeptides N-protected with 1-naphthoyl and 2-naphthylacetyl groups. The 2-naphthylacetyl group was extensively reported for preparation of peptide-based self-assembled hydrogels, whereas the 1-naphthaloyl group was largely overlooked, owing presumably to the lack of a methylene linker between the naphthalene aromatic ring and the peptide backbone. Interestingly, dehydrodipeptides N-capped with the 1-naphthyl moiety afford stronger gels, at lower concentrations, than the 2-naphthylacetyl-capped dehydrodipeptides. Fluorescence and circular dichroism spectroscopy showed that the self-assembly of the dehydrodipeptides is driven by intermolecular aromatic π-π stacking interactions. Molecular dynamics simulations revealed that the 1-naphthoyl group allows higher order aromatic π-π stacking of the peptide molecules than the 2-naphthylacetyl group, together with hydrogen bonding of the peptide scaffold. The nanostructure of the gel networks was studied by TEM and STEM microscopy and was found to correlate well with the elasticity of the gels. This study contributes to understanding the interplay between peptide and capping group structure on the formation of self-assembled low-molecular-weight peptide hydrogels. Moreover, the results presented here add the 1-naphthoyl group to the palette of capping groups available for the preparation of efficacious low-molecular-weight peptide-based hydrogels.

Recent Advances in Strategies to Combat Bacterial Drug Resistance: Antimicrobial Materials and Drug Delivery Systems

Bacterial infection is a common clinical disease. Antibiotics have saved countless lives since their discovery and are a powerful weapon in the fight against bacteria. However, with the widespread use of antibiotics, the problem of drug resistance now poses a great threat to human health. In recent years, studies have investigated approaches to combat bacterial resistance. Several antimicrobial materials and drug delivery systems have emerged as promising strategies. Nano-drug delivery systems for antibiotics can reduce the resistance to antibiotics and extend the lifespan of novel antibiotics, and they allow targeting drug delivery compared to conventional antibiotics. This review highlights the mechanistic insights of using different strategies to combat drug-resistant bacteria and summarizes the recent advancements in antimicrobial materials and drug delivery systems for different carriers. Furthermore, the fundamental properties of combating antimicrobial resistance are discussed, and the current challenges and future perspectives in this field are proposed.

Silver-Nanoparticle-Embedded Short Amphiphilic Peptide Nanostructures and Their Plausible Application to Reduce Bacterial Infections

The microbiota-gut-brain axis (GBA) plays a critical role in the development of neurodegenerative diseases. Dysbiosis of the intestinal microbiome causes a significant alteration in the gut microbiota of Alzheimer's disease (AD) patients, followed by neuroinflammatory processes. Thus, AD beginning in the gut is closely related to an imbalance in gut microbiota, and hence a multidomain approach to reduce this imbalance by exerting positive effects on the gut microbiota is needed. In one example, a tyrosine-based short peptide amphiphile (sPA) was used to synthesize antibacterial AgNPs-sPA nanostructures. Such nanostructures showed high biocompatibility and low cytotoxicity, and therefore work as model drug delivery agents for addressing local bacterial infections. These may have therapeutic value for the treatment of microbiota-triggered progression of neurodegenerative diseases.

Bio-Tailored Sensing at the Nanoscale: Biochemical Aspects and Applications

The demonstration of the first enzyme-based electrode to detect glucose, published in 1967 by S. J. Updike and G. P. Hicks, kicked off huge efforts in building sensors where biomolecules are exploited as native or modified to achieve new or improved sensing performances. In this growing area, bionanotechnology has become prominent in demonstrating how nanomaterials can be tailored into responsive nanostructures using biomolecules and integrated into sensors to detect different analytes, e.g., biomarkers, antibiotics, toxins and organic compounds as well as whole cells and microorganisms with very high sensitivity. Accounting for the natural affinity between biomolecules and almost every type of nanomaterials and taking advantage of well-known crosslinking strategies to stabilize the resulting hybrid nanostructures, biosensors with broad applications and with unprecedented low detection limits have been realized. This review depicts a comprehensive collection of the most recent biochemical and biophysical strategies for building hybrid devices based on bioconjugated nanomaterials and their applications in label-free detection for diagnostics, food and environmental analysis.

Natural Piezoelectric Biomaterials: A Biocompatible and Sustainable Building Block for Biomedical Devices

The piezoelectric effect has been widely observed in biological systems, and its applications in biomedical field are emerging. Recent advances of wearable and implantable biomedical devices bring promise as well as requirements for the piezoelectric materials building blocks. Owing to their biocompatibility, biosafety, and environmental sustainability, natural piezoelectric biomaterials are known as a promising candidate in this emerging field, with a potential to replace conventional piezoelectric ceramics and synthetic polymers. Herein, we provide a thorough review of recent progresses of research on five major types of piezoelectric biomaterials including amino acids, peptides, proteins, viruses, and polysaccharides. Our discussion focuses on their structure- and phase-related piezoelectric properties and fabrication strategies to achieve desired piezoelectric phases. We compare and analyze their piezoelectric performance and further introduce and comment on the approaches to improve their piezoelectric property. Representative biomedical applications of this group of functional biomaterials including energy harvesting, sensing, and tissue engineering are also discussed. We envision that molecular-level understanding of the piezoelectric effect, piezoelectric response improvement, and large-scale manufacturing are three main challenges as well as research and development opportunities in this promising interdisciplinary field.

Gram-selective antibacterial peptide hydrogels

The human microbiome plays fundamental roles in human health and disease. However, widely used broad-spectrum antibiotics severely disrupt human-related microbial communities, eventually leading to resistant bacteria, posing a growing threat to global medical health. Antimicrobial peptides (AMPs) are promising antimicrobial agents that barely cause bacterial resistance. Excellent broad-spectrum antimicrobial activities have been achieved using hydrogels self-assembled from AMPs, but there is still a lack of AMP hydrogels that can target Gram-positive and Gram-negative bacteria. Herein, several hydrogels self-assembled from AMPs, termed IK1, IK3, and IK4, were designed and synthesized. In vitro antibacterial results indicated that the IK1 and IK4 hydrogels specifically targeted Gram-positive and Gram-negative bacteria, respectively, while the IK3 hydrogel targeted both Gram-positive and Gram-negative bacteria. The desired broad-spectrum or Gram-selective AMP hydrogels are believed to be obtained through the rational design of the hydrophilicity, hydrophobicity, and charge properties of the peptide molecules. Good in vivo Gram-selective antibacterial properties and the ability to promote wound healing have been demonstrated via treating mouse wound models with these AMP hydrogels. We believe that these Gram-selective AMP hydrogels could potentially have important applications in treating common recurring infections.

Skin-like wound dressings with on-demand administration based on in situ peptide self-assembly for skin regeneration

Burn injuries without the normal skin barrier usually cause skin wound infections, and wound dressings are necessary. Although various dressings with antibacterial ability have already been developed, the biosafety and administration mode are still bottleneck problems for further application. Herein, we designed skin-like wound dressings based on silk fibroin (SF), which are modified with the gelatinase-cleavable self-assembled/antibacterial peptide (GPLK) and epidermal growth factor (EGF). When a skin wound is infected, the gelatinase over-secreted by bacteria can cut the GPLK peptides, leading to the in situ self-assembly of peptides and the resultant high-efficiency sterilization. Compared with the commercial antibacterial dressing, the SF-GPLK displayed a faster wound healing rate. When a skin wound is not infected, the GPLK peptides remain in the SF, realizing good biosafety. Generally, the EGF can be released to promote wound healing and skin regeneration in both cases. Therefore, skin-like SF-GPLK wound dressings with on-demand release of antibacterial peptides provide a smart administration mode for clinical wound management and skin regeneration.

Synthesis and Organization of Gold-Peptide Nanoparticles for Catalytic Activities

A significant development in the synthesis strategies of metal-peptide composites and their applications in biomedical and bio-catalysis has been reported. However, the random aggregation of gold nanoparticles provides the opportunity to find alternative fabrication strategies of gold-peptide composite nanomaterials. In this study, we used a facile strategy to synthesize the gold nanoparticles via a green and simple approach where they show self-alignment on the assembled nanofibers of ultrashort oligopeptides as a composite material. A photochemical reduction method is used, which does not require any external chemical reagents for the reduction of gold ions, and resultantly makes the gold nanoparticles of size ca. 5 nm under mild UV light exposure. The specific arrangement of gold nanoparticles on the peptide nanofibers may indicate the electrostatic interactions of two components and the interactions with the amino group of the peptide building block. Furthermore, the gold-peptide nanoparticle composites show the ability as a catalyst to degradation of environmental pollutant p-nitrophenol to p-aminophenol, and the reaction rate constant for catalysis is calculated as 0.057 min-1 at a 50-fold dilute sample of 2 mg/mL and 0.72 mM gold concentration in the composites. This colloidal strategy would help researchers to fabricate the metalized bioorganic composites for various biomedical and bio-catalysis applications.

Green Fabrication of Bioactive Silver Nanoparticles Using Mentha pulegium Extract under Alkaline: An Enhanced Anticancer Activity

Fabrication of silver nanoparticles (AgNPs) using Chinese herbal medicine is popular as the bioactive components included in them would generate potential synergistic effect with the metal nanoparticles. The leaf of Mentha pulegium, whose extract contains a range of phytochemicals and exhibits a wide spectrum of bioactivities, is used as Chinese herbal medicine after drying naturally. Thus, the green synthesis of AgNPs using Mentha pulegium has aroused interests from analysts. However, the biosynthesis of AgNPs under alkaline conditions and the biological activities remain elusive, where alkaline conditions may influence the physicochemical properties and the biological activities of biosynthesized AgNPs. In this study, we were stimulated to fabricate bioactive AgNPs using Mentha pulegium extract under alkaline conditions, accompanied by a systematic evaluation on the effect of biosynthesis parameters on the formation, average size, and polydispersity of AgNPs. Our results showed that alkaline conditions could accelerate the formation of AgNPs with a small average size but at a disadvantage to the polydispersity. Additionally, the as-prepared AgNPs had a hexagonal structure and spherical shape with an average size of 15.7 ± 0.1 nm, existing in the monodispersed form and revealing a high degree of stability. The AgNPs exhibited potent antioxidant and significant inhibitory activity for both bacterial and cancer cell lines. The MIC values of AgNPs for Staphylococcus aureus and Escherichia coli were both 50.0 μg·mL-1, and the IC50 values for HCT116, HepG2, and HeLa cells were 9.0, 14.5, and 31.5 μg·mL-1, respectively. The AgNPs biosynthesized using M. pulegium under alkaline conditions, which had a smaller size and more surface loads, are entirely different with those synthesized under acidic conditions, and the anticancer activity increased significantly. The internalization of AgNPs inside these five cells displayed a variant trend with variable AgNPs concentrations, suggesting the different mechanism of cell death. For two pathogens, HCT116 and HepG2 cancer cell lines, both cell wall and intracellular damage may be responsible for the cell death. However, for Hela cell line the cell death may be rooted in oxidative stress or intracellular penetration. These results confirmed that the AgNPs biosynthesized from M. pulegium extract under alkaline conditions would act as better anticancer agents in biomedicine.

Silver Micro-Nanoparticle-Based Nanoarchitectures: Synthesis Routes, Biomedical Applications, and Mechanisms of Action

Silver has become a potent agent that can be effectively applied in nanostructured nanomaterials with various shapes and sizes against antibacterial applications. Silver nanoparticle (Ag NP) based-antimicrobial agents play a major role in different applications, including biomedical applications, as surface treatment and coatings, in chemical and food industries, and for agricultural productivity. Due to advancements in nanoscience and nanotechnology, different methods have been used to prepare Ag NPs with sizes and shapes reducing toxicity for antibacterial applications. Studies have shown that Ag NPs are largely dependent on basic structural parameters, such as size, shape, and chemical composition, which play a significant role in preparing the appropriate formulation for the desired applications. Therefore, this review focuses on the important parameters that affect the surface interaction/state of Ag NPs and their influence on antimicrobial activities, which are essential for designing future applications. The mode of action of Ag NPs as antibacterial agents will also be discussed.