Probiotic cellulose: Antibiotic-free biomaterials with enhanced antibacterial activity

Probiotic-Based Mineralized Living Materials to Produce Antimicrobial Yogurts

Mineralization of living cells represents an evolutionary adaptation that enhances cellular resilience to physicochemical stress. Inspired by this strategy, we have here developed hybrid living materials (HLMs), incorporating probiotics into mineralized collagen 3D matrices, with the aim of protecting and promoting the successful oral delivery of the bacteria. Collagen fibrils are simultaneously self-assembled and mineralized in the presence of the probiotics (Lactobacillus acidophilus, La, was used as model), resulting in the integration of the probiotics into the hybrid matrix (i.e., bulk encapsulation). During this process, probiotics are also coated with a nanofilm of apatite mineral (single-cell encapsulation), which provides them with extra protection and reinforces their viability and activity. In fact, the resulting HLM is metabolically active, and maintain the capacity to ferment milk into yogurt with antibacterial activity against the two major foodborne pathogens Pseudomonas aeruginosa (Pa) and Staphylococcus aureus (Sa). Interestingly, the HLM provides probiotics an additional protection in the gastrointestinal environment (i.e., simulated gastric fluid), which is of special interest for healthcare materials for oral administration. The results pave the way for the creation of innovative healthcare materials with enhanced functionalities and the potential to produce probiotic foods with notable antimicrobial properties.

Co-cultivation of Komagataeibacter sp. and Lacticaseibacillus sp. strains to produce bacterial nanocellulose-hyaluronic acid nanocomposite membranes for skin wound healing applications

Inspired by natural microbial cooperation, a co-culture approach was used to synthesize bacterial nanocellulose (BNC)-based nanocomposites for potential wound healing applications. By co-culturing either Komagataeibacter xylinus (K1G4) or the never tested strain K. rhaeticus (K2G46) with the hyaluronic acid (HA)-producer Lacticaseibacillus casei UMCC 2535, two BNC-HA nanocomposites were obtained (C1-K1 and C2-K2). The membranes showed a HA content of 0.49 ± 0.05 mg (C1-K1) and 1.40 ± 0.07 mg (C2-K2), and both revealing a nearly complete release of HA after 1 h in PBS. Compared to pure BNC membranes, the nanocomposites showed enhanced properties, including higher crystallinity (K1G4 = 84.6 %; K2G46 = 76.5 %; C1-K1 = 89.1 %; C2-K2 = 88.1 %), and Young's modulus (K1G4 = 3.38 ± 0.56 GPa; K2G46 = 2.22 ± 0.65 GPa; C1-K1 = 10.00 ± 1.32 GPa; C2-K2 = 7.90 ± 1.54 GPa). Additionally, both BNC-HA membranes exhibited increased moisture uptake (K1G4 = 9.06 ± 0.47 %; K2G46 = 9.27 ± 1.33 %; C1-K1 = 13.65 ± 0.53 %; C2-K2 = 16.26 ± 1.05 %) and water absorption (K1G4 = 82.18 ± 5.25 %; K2G46 = 86.54 ± 7.86 %; C1-K1 = 160.04 ± 9.33 %; C2-K2 = 144.42 ± 13.86 %) capacity. Moreover, they were non-cytotoxic towards human keratinocyte (HaCaT) cells, with >90 % cell viability for up to 72 h. The in vitro scratch assays showed a complete wound closure within 48 h for cells exposed to BNC-HA membranes. These findings underscore the potential of co-culturing system to develop BNC-HA nanocomposites for wound healing applications.

Complete Genome Sequence and Probiotic Properties of Pediococcus acidilactici CLP03 Isolated from Healthy Felis catus

Probiotics are available from various sources, including the gastrointestinal tract of healthy animals. In this study, Pediococcus acidilactici was isolated for the first time from Felis catus and evaluated for its functionality. The findings revealed that P. acidilactici CLP03 exhibited inhibitory properties against pathogenic bacteria (E. coli, Salmonella, S. aureus, P. aeruginosa, and L. monocytogenes). Then, survival of strains exposed to pH 2.5, 0.3% bile salts, 0.5% bile salts, and gastrointestinal fluids was 63.97%, 98.84%, 87.95%, and 52.45%, respectively. Also, P. acidilactici CLP03 demonstrated high hydrophobicity (69.63-82.03%) and self-aggregation (73.51-81.44%), negative for hemolytic, and was susceptible to clindamycin. Finally, the scavenging rates of DPPH, ABTS, and O2- were 53.55%, 54.81%, and 85.13%, respectively, which demonstrated that the strain CLP03 has good oxidation resistance. All these characteristics contribute to the survival, colonization, and functionality of the strain in the gastrointestinal tract, indicating their excellent probiotic potential. On the other hand, animal experiments (KM mice, randomly assigned to four groups) showed that the gavage of CLP03 had no toxic effects on mice, increased the serum SOD content, and decreased the MDA and BUN contents, which revealed gavage of CLP03 significantly increased the antioxidant capacity of mice in vivo. In addition, complete genome annotation showed that P. acidilactici CLP03 had 1976 CDS genes, and the numbers of CRISPR, gene islands, and phages were 8, 3, and 6, respectively. In conclusion, P. acidilactici CLP03 could be a candidate functional cat probiotic to enhance animal health and welfare.

Bacterial Cellulose as a UVB Filter to Protect the Skin Microbiota

Certain aerobic bacteria produce bacterial cellulose (BC) to protect themselves from UV radiation. Inspired by this natural function, the UV-filtering capacity of wet BC film (BC) and dried BC (BC-Dried) is evaluated and it is concluded that both samples hardly filter UVA, but filter UVB to some extent, especially BC-Dried. Moreover, this filtering capacity does not diminish but significantly increases with time, with efficiencies in the 145-160 min time range equal to or greater than most UV filters of the market. This increase in efficiency is due to the fact that the BC structure is modified by prolonged exposure to UVB radiation. Specifically, UVB causes sintering of the cellulose fibers, making the structure denser and increasing its reflection and scattering of UVB radiation. Remarkably, this UVB filtering ability of BC allows it to protect key skin probiotics, Lactobacillus fermentum (L. fermentum) and Cutibacterium acnes (C. acnes), against UVB damage. While the protection of healthy skin microbiota is not currently a regulatory requirement for sunscreens with UV filters, it may become a key differentiator for future UV filters given the increasing evidence on the role of skin microbiota in health.

Applications of bacterial cellulose in the food industry and its health-promoting potential

Bacterial cellulose (BC) is a naturally occurring biomaterial with a wide range of potential applications in the food industry because of its exceptional mechanical qualities, unique nanofiber structure, high purity, and outstanding biocompatibility. Beyond its physical attributes, BC has gained interest recently due to research demonstrating its potential health benefits as a functional food ingredient. This article examines the many uses of BC in the food business, with a focus on how it may enhance food texture, operate as a bioactive carrier, and have promise in the packaging sector. Further research was done on the health-promoting properties of BC in functional foods, particularly with regard to its functions as a blood glucose regulator, and gastrointestinal health. This review seeks to bring fresh ideas for the study of bioactive components in the food industry by providing a summary of the existing research and demonstrating the possible role of BC in food. It also suggests future paths for research.

Probiotic-Loaded Bacterial Cellulose as an Alternative to Combat Carbapenem-Resistant Bacterial Infections

Background: Carbapenems are one of the mainstays of treatment for antibiotic-resistant bacteria (ARB). This has made the rise of carbapenem-resistant bacteria a threat to global health. In fact, the World Health Organization (WHO) has identified carbapenem-resistant bacteria as critical pathogens, and the development of novel antibacterials capable of combating infections caused by these bacteria is a priority. Objective: With the aim of finding new alternatives to fight against ARB and especially against carbapenem-resistant bacteria, we have developed a series of living materials formed by incorporating the probiotics Lactobacillus plantarum (Lp), Lactobacillus fermentum (Lf), and a mixture of both (L. plantarum+L. fermentum) into bacterial cellulose (BC). Results: These probiotic-loaded bacterial celluloses inhibited the proliferation of three ARB, including two carbapenem-resistant enterobacteria (CRE), identified as Klebsiella pneumoniae and Enterobacter cloacae, and a carbapenem-resistant Pseudomonas aeruginosa. Interestingly, while the probiotics L. plantarum, L. fermentum, and the mixture of both were found to be inactive against these ARB, they became active once incorporated into BC. Conclusions: The increase in activity is due to the known effect that cells increase their activity once incorporated into a suitable matrix, forming a living material. For the same reasons, the probiotics in the living materials BC-L. plantarum, BC-L. fermentum, and BC-L. plantarum+L. fermentum showed increased stability, allowing them to be stored with bacterial activity for long periods of time (two months).

Advances in Smart-Response Hydrogels for Skin Wound Repair

Hydrogels have emerged as promising candidates for biomedical applications, especially in the treatment of skin wounds, as a result of their unique structural properties, highly tunable physicochemical properties, and excellent biocompatibility. The integration of smart-response features into hydrogels allows for dynamic responses to different external or internal stimuli. Therefore, this paper reviews the design of different smart-responsive hydrogels for different microenvironments in the field of skin wound therapy. First, the unique microenvironments of three typical chronic difficult-to-heal wounds and the key mechanisms affecting wound healing therapeutic measures are outlined. Strategies for the construction of internal stimulus-responsive hydrogels (e.g., pH, ROS, enzymes, and glucose) and external stimulus-responsive hydrogels (e.g., temperature, light, electricity, and magnetic fields) are highlighted from the perspective of the wound microenvironment and the in vitro environment, and the constitutive relationships between material design, intelligent response, and wound healing are revealed. Finally, this paper discusses the severe challenges faced by smart-responsive hydrogels during skin wound repair and provides an outlook on the combination of smart-responsive hydrogels and artificial intelligence to give scientific direction for creating and using hydrogel dressings that respond to stimuli in the clinic.

Global Trends and Scientific Impact of Topical Probiotics in Dermatological Treatment and Skincare

The skin plays a crucial role in maintaining homeostasis and protecting against external aggressors. Recent research has highlighted the potential of probiotics and postbiotics in dermatological treatments and skincare. These beneficial microorganisms interact with the skin microbiota, modulate the immune response, and enhance the skin barrier, offering a promising therapeutic avenue for various skin conditions, such as acne, dermatitis, eczema, and psoriasis. This bibliometric study aims to analyze the global trends and scientific impact of topical probiotics in dermatology. By reviewing 106 articles published between 2013 and 2023, the study categorizes the applications of probiotics in wound healing, inflammatory skin diseases, and general skincare. The findings indicate a significant increase in publications from 2021 onwards, attributed to the heightened focus on medical research during the COVID-19 pandemic. This study also identifies the most productive countries, institutions, and authors in this field, highlighting the importance of international collaborations. The results underscore the efficacy of probiotic-based topical formulations in improving skin health, reducing inflammation, and enhancing wound healing. This comprehensive analysis supports the development of new therapeutic strategies based on topical probiotics and encourages high-quality research in this promising area.

Potential Probiotic Properties and Complete Genome Analysis of Limosilactobacillus reuteri LRA7 from Dogs

This study aimed to isolate and screen canine-derived probiotics with excellent probiotic properties. Strain characterization was conducted using a combination of in vitro and in vivo probiotic characterization and safety assessments, as well as complete genome analysis. The results showed that Limosilactobacillus reuteri LRA7 exhibited excellent bacteriostatic and antioxidant activities. The survival rate at pH 2.5 was 79.98%, and the viable counts after exposure to gastrointestinal fluid and 0.5% bile salts were 7.77 log CFU/mL and 5.29 log CFU/mL, respectively. The bacterium also exhibited high hydrophobicity, self-coagulation, and high temperature tolerance, was negative for hemolysis, and was sensitive to clindamycin. In vivo studies in mice showed that the serum superoxide dismutase activity level was 53.69 U/mL higher in the MR group of mice compared to that of the control group, the malondialdehyde content was 0.53 nmol/mL lower in the HR group, and the highest jejunal V/C value was 4.11 ± 1.05 in the HR group (p < 0.05). The L. reuteri LRA7 gene is 2.021 megabases in size, contains one chromosome and one plasmid, and is annotated with 1978 functional genes. In conclusion, L. reuteri LRA7 has good probiotic potential and is safe. It can be used as an ideal probiotic candidate strain of canine origin.

Intestinal Delivery of Probiotics: Materials, Strategies, and Applications

Probiotics with diverse and crucial properties and functions have attracted broad interest from many researchers, who adopt intestinal delivery of probiotics to modulate the gut microbiota. However, the major problems faced for the therapeutic applications of probiotics are the viability and colonization of probiotics during their processing, oral intake, and subsequent delivery to the gut. The challenges of simple oral delivery (stability, controllability, targeting, etc.) have greatly limited the use of probiotics in clinical therapies. Nanotechnology can endow the probiotics to be delivered to the intestine with improved survival rate and increased resistance to the adverse environment. Additionally, the progress in synthetic biology has created new opportunities for efficiently and purposefully designing and manipulating the probiotics. In this article, a brief overview of the types of probiotics for intestinal delivery, the current progress of different probiotic encapsulation strategies, including the chemical, physical, and genetic strategies and their combinations, and the emerging single-cell encapsulation strategies using nanocoating methods, is presented. The action mechanisms of probiotics that are responsible for eliciting beneficial effects are also briefly discussed. Finally, the therapeutic applications of engineered probiotics are discussed, and the future trends toward developing engineered probiotics with advanced features and improved health benefits are proposed.

Photopolymerizable and Antibacterial Hydrogels Loaded with Metabolites from Lacticaseibacillus rhamnosus GG for Infected Wound Healing

In response to increasing antibiotic resistance and the pressing demand for safer infected wound care, probiotics have emerged as promising bioactive agents. To address the challenges associated with the safe and efficient application of probiotics, this study successfully loaded metabolites from Lacticaseibacillus rhamnosus GG (LGG) into a gelatin cross-linked macromolecular network by an in situ blending and photopolymerization method. The obtained LM-GelMA possesses injectability and autonomous healing capabilities. Importantly, the incorporation of LGG metabolites endows LM-GelMA with excellent antibacterial properties against Staphylococcus aureus and Escherichia coli, while maintaining good biocompatibility. In vivo assessments revealed that LM-GelMA can accelerate wound healing by mitigating infections induced by pathogenic bacteria. This is accompanied by a reduction in the expression of key proinflammatory cytokines such as TNF-α, IL-6, VEGFR2, and TGF-β, leading to increased re-epithelialization and collagen formation. Moreover, microbiological analysis confirmed that LM-GelMA can modulate the abundance of beneficial wound microbiota at family and genus levels. This study provides a facile strategy and insights into the functional design of hydrogels from the perspective of wound microenvironment regulation.

From Nature to Lab: Sustainable Bacterial Cellulose Production and Modification with Synthetic Biology

Bacterial cellulose (BC) is a macromolecule with versatile applications in medicine, pharmacy, biotechnology, cosmetology, food and food packaging, ecology, and electronics. Although many bacteria synthesize BC, the most efficient BC producers are certain species of the genera Komagataeibacter and Novacetimonas. These are also food-grade bacteria, simplifying their utilization at industrial facilities. The basic principles of BC synthesis are known from studies of Komagataeibacter xylinus, which became a model species for studying BC at genetic and molecular levels. Cellulose can also be of plant origin, but BC surpasses its purity. Moreover, the laboratory production of BC enables in situ modification into functionalized material with incorporated molecules during its synthesis. The possibility of growing Komagataeibacter and Novacetimonas species on various organic substrates and agricultural and food waste compounds also follows the green and sustainable economy principles. Further intervention into BC synthesis was enabled by genetic engineering tools, subsequently directing it into the field of synthetic biology. This review paper presents the development of the fascinating field of BC synthesis at the molecular level, seeking sustainable ways for its production and its applications towards genetic modifications of bacterial strains for producing novel types of living biomaterials using the flexible metabolic machinery of bacteria.

Nanocellulose Sponges Containing Antibacterial Basil Extract

Nanocellulose (NC) is a valuable material in tissue engineering, wound dressing, and drug delivery, but its lack of antimicrobial activity is a major drawback for these applications. In this work, basil ethanolic extract (BE) and basil seed mucilage (BSM) were used to endow nanocellulose with antibacterial activity. NC/BE and NC/BE/BSM sponges were obtained from nanocellulose suspensions and different amounts of BE and BSM after freeze-drying. Regardless of the BE or BSM content, the sponges started to decompose at a lower temperature due to the presence of highly volatile active compounds in BE. A SEM investigation revealed an opened-cell structure and nanofibrillar morphology for all the sponges, while highly impregnated nanofibers were observed by SEM in NC/BE sponges with higher amounts of BE. A quantitative evaluation of the porous morphology by microcomputer tomography showed that the open porosity of the sponges varied between 70% and 82%, being lower in the sponges with higher BE/BSM content due to the impregnation of cellulose nanofibers with BE/BSM, which led to smaller pores. The addition of BE increased the specific compression strength of the NC/BE sponges, with a higher amount of BE having a stronger effect. A slight inhibition of S. aureus growth was observed in the NC/BE sponges with a higher amount of BE, and no effect was observed in the unmodified NC. In addition, the NC/BE sponge with the highest amount of BE and the best antibacterial effect in the series showed no cytotoxic effect and did not interfere with the normal development of the L929 cell line, similar to the unmodified NC. This work uses a simple, straightforward method to obtain highly porous nanocellulose structures containing antibacterial basil extract for use in biomedical applications.

Photodynamic Therapy, Probiotics, Acetic Acid, and Essential Oil in the Treatment of Chronic Wounds Infected with Pseudomonas aeruginosa

As a prevalent medical problem that burdens millions of patients across the world, chronic wounds pose a challenge to the healthcare system. These wounds, often existing as a comorbidity, are vulnerable to infections. Consequently, infections hinder the healing process and complicate clinical management and treatment. While antibiotic drugs remain a popular treatment for infected chronic wounds, the recent rise of antibiotic-resistant strains has hastened the need for alternative treatments. Future impacts of chronic wounds are likely to increase with aging populations and growing obesity rates. With the need for more effective novel treatments, promising research into various wound therapies has seen an increased demand. This review summarizes photodynamic therapy, probiotics, acetic acid, and essential oil studies as developing antibiotic-free treatments for chronic wounds infected with Pseudomonas aeruginosa. Clinicians may find this review informative by gaining a better understanding of the state of current research into various antibiotic-free treatments. Furthermore. this review provides clinical significance, as clinicians may seek to implement photodynamic therapy, probiotics, acetic acid, or essential oils into their own practice.

Quaternary Ammonium Salts: Insights into Synthesis and New Directions in Antibacterial Applications

The overuse of antibiotics has led to the emergence of a large number of antibiotic-resistant genes in bacteria, and increasing evidence indicates that a fungicide with an antibacterial mechanism different from that of antibiotics is needed. Quaternary ammonium salts (QASs) are a biparental substance with good antibacterial properties that kills bacteria through simple electrostatic adsorption and insertion into cell membranes/altering of cell membrane permeability. Therefore, the probability of bacteria developing drug resistance is greatly reduced. In this review, we focus on the synthesis and application of single-chain QASs, double-chain QASs, heterocyclic QASs, and gemini QASs (GQASs). Some possible structure-function relationships of QASs are also summarized. As such, we hope this review will provide insight for researchers to explore more applications of QASs in the field of antimicrobials with the aim of developing systems for clinical applications.

Living Cellulose Materials with Tunable Viscoelasticity through Probiotic Proliferation

Probiotic cellulose (PC), a living material (LM) consisting of probiotics integrated into bacterial cellulose, is the first example where life (probiotic proliferation) is the input to tune the viscoelasticity of the biomaterial. The gradual proliferation of probiotics within the matrix acts as a key modulator of the cellulose viscoelasticity, providing from celluloses with lower-than-matrix viscoelasticity to celluloses with viscoelastic moduli closer to those of elastic solids. This concept is a promising approach to producing living bio-ink with tunable viscoelastic response of special interest for specific applications such as 3D printing. In contrast to the most common hydrogels with stimuli-tunable mechanical properties, which require external stimuli such as mechanical stress, UV radiation, or heat, this living bio-ink only requires time to tune from a fluid-like into a solid-like biomaterial.

MRSA compendium of epidemiology, transmission, pathophysiology, treatment, and prevention within one health framework

Staphylococcus aureus is recognized as commensal as well as opportunistic pathogen of humans and animals. Methicillin resistant strain of S. aureus (MRSA) has emerged as a major pathogen in hospitals, community and veterinary settings that compromises the public health and livestock production. MRSA basically emerged from MSSA after acquiring SCCmec element through gene transfer containing mecA gene responsible for encoding PBP-2α. This protein renders the MRSA resistant to most of the β-lactam antibiotics. Due to the continuous increasing prevalence and transmission of MRSA in hospitals, community and veterinary settings posing a major threat to public health. Furthermore, high pathogenicity of MRSA due to a number of virulence factors produced by S. aureus along with antibiotic resistance help to breach the immunity of host and responsible for causing severe infections in humans and animals. The clinical manifestations of MRSA consist of skin and soft tissues infection to bacteremia, septicemia, toxic shock, and scalded skin syndrome. Moreover, due to the increasing resistance of MRSA to number of antibiotics, there is need to approach alternatives ways to overcome economic as well as human losses. This review is going to discuss various aspects of MRSA starting from emergence, transmission, epidemiology, pathophysiology, disease patterns in hosts, novel treatment, and control strategies.

Biofilm-based delivery approaches and specific enrichment strategies of probiotics in the human gut

The use of probiotics has been one of the effective strategies to restructure perturbed human gut microbiota following a disease or metabolic disorder. One of the biggest challenges associated with the use of probiotic-based gut modulation strategies is to keep the probiotic cells viable and stable during the gastrointestinal transit. Biofilm-based probiotics delivery approaches have emerged as fascinating modes of probiotic delivery in which probiotics show significantly greater tolerance and biotherapeutic potential, and interestingly probiotic biofilms can be developed on food-grade surfaces too, which is ideal for the growth and proliferation of bacterial cells for incorporation into food matrices. In addition, biofilms can be further encapsulated with food-grade materials or with bacterial self-produced biofilms. This review presents a newly emerging and unprecedently discussed techniques for the safe delivery of probiotics based on biofilms and further discusses newly emerging prebiotic materials which target specific gut microbiota groups for growth and proliferation.

Novel Probiotic/Bacterial Cellulose Biocatalyst for the Development of Functional Dairy Beverage

The development of innovative functional products with potential health benefits, under the concept of bio-economy, is flourishing. This study undertook an evaluation of non-dairy lactobacilli Lactiplantibacillus pentosus B329 and Lactiplantibacillus plantarum 820 as “ready to use” starter cultures. Lactic acid bacteria (LAB) cultures were evaluated for their fermentation efficiency, before and after freeze-drying, using cheese whey (CW) as a fermentation substrate and subsequent immobilization on bacteria cellulose (BC) to produce a novel biocatalyst. The biocatalyst was applied in functional sour milk production and compared with free cells via the assessment of physicochemical and microbiological properties and sensory evaluation. Evidently, LAB strains exhibited high fermentative activity before and after freeze-drying. Results of a 5-month storage stability test showed that viability was 19% enhanced by immobilization on BC, supporting the concept of “ready to use” cultures for the production of fermented beverages. Likewise, sour milk produced by the BC biocatalyst presented higher organoleptic scores, compared to the free cells case, whereas immobilization on BC enhanced probiotic viability during post-fermentation storage (4 °C, 28 days). The obtained high viability (>107 log cfu/g) demonstrated the efficacy of the proposed bioprocess for the production of functional/probiotic-rich beverages. Ultimately, this work presents a consolidated scheme that includes the advantages and the cooperative effect of probiotic LAB strains combined with a functional biopolymer (BC) towards the formulation of novel functional products that coincide with the pillars of food systems sustainability.

Ti3C2Tx MXene loaded with indocyanine green for synergistic photothermal and photodynamic therapy for drug-resistant bacterium

Infections caused by antibiotic-resistant bacteria are a critical threat to human health. Considering the difficulties and time-consuming nature of synthesizing new antibiotics, it is of great significance and importance to develop the antibiotic-independent antibacterial approaches against drug-resistant bacteria. Nanomaterials-based photothermal therapy (PTT) and photodynamic therapy (PDT) have attracted much attention due to their broad-spectrum bactericidal activity, low toxicity, and drug-free feature. In this work, we loaded indocyanine green (ICG) on the Ti₃C₂T_x MXene nanosheets (454 nm) so as to combine the photothermal effect of MXene with the photodynamic effect of ICG. Without near-infrared (NIR) irradiation, MXene (20 μg/mL), ICG (5 μg/mL) or ICG-loaded MXene (ICG-MXene) showed no significant antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). Under NIR, however, the viability loss of MRSA remarkably increased to 45% for MXene, 66% for ICG and 100% for ICG-MXene. We further found that the great anti-MRSA activity of ICG-MXene under NIR was attributed to the combination of photothermal effect of MXene (high temperature) and photodynamic effect of ICG (high level of reactive oxygen species). Our findings indicate that MXene can be used as both the photothermal agent and the carrier of photosensitizers to achieve the synergistic PTT/PDT therapy for bacterial infections.

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.

Size-dependent photothermal antibacterial activity of Ti3C2Tx MXene nanosheets against methicillin-resistant Staphylococcus aureus

Developing antibiotics-independent antibacterial materials is of great importance for combating drug-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA). MXene (transition metal carbides and nitrides), a class of novel 2D nanomaterials, has shown great potentials in biomedical areas. However, the effect of MXene size on its properties and bioactivity is still unknown. Herein, we report for the first time that the antibacterial photothermal therapy efficacy of Ti₃C₂T_x MXene nanosheets is size-dependent. Three MXene suspensions with small size of 196 nm (MX-s), medium size of 347 nm (MX-m) and large size of 497 nm (MX-l) were prepared via ultrasonication. Upon NIR irradiation for 5 min, the temperature of MXene suspensions (10 μg/mL) increased to 64, 60 and 56 °C for MX-s, MX-m and MX-l, respectively. Accordingly, the viability loss of MRSA induced by MX-s, MX-m and MX-l under NIR was 93%, 69% and 56%, respectively. The in vivo study in the MRSA-infected mouse model showed that the photothermal therapy efficacy of MX-s was comparable to that of the positive control vancomycin. This is the first report on the size-dependent photothermal effect and photothermal antibacterial activity of MXene, which may guide the development of MXene-based therapeutics in the future. In addition, the drug-free antibacterial therapy has great implications for the treatment of antibiotics-resistant bacteria infections.

Multifunctional applications of natural polysaccharide starch and cellulose: An update on recent advances

The emergence of clinical complications and therapeutic challenges for treating various diseases necessitate the discovery of novel restorative functional materials. Polymer-based drug delivery systems have been extensively reported in the last two decades. Recently, there has been an increasing interest in the progression of natural biopolymers based controlled therapeutic strategies, especially in drug delivery and tissue engineering applications. However, the solubility and functionalisation due to their complex network structure and intramolecular bonding seem challenging. This review explores the current advancement and prospects of the most promising natural polymers such as cellulose, starch and their derivatives-based drug delivery vehicles like hydrogels, films and composites, in combating major ailments such as bone infections, microbial infections, and cancers. In addition, selective drug targeting using metal-drug (MD) and MD-based polymeric missiles have been exciting but challenging for its application in cancer therapeutics. Owing to high biocompatibility of starch and cellulose, these materials have been extensively evaluated in biomedical and pharmaceutical applications. This review presents a detailed impression of the current trends for the construction of biopolymer-based tissue engineering, drug/gene/protein delivery vehicles.

Integrating Porphyrinic Metal-Organic Frameworks in Nanofibrous Carrier for Photodynamic Antimicrobial Application

The rise and spread of antimicrobial resistance is creating an ever greater challenge in wound management. Nanofibrous membranes (NFMs) incorporated with antibiotics have been widely used to remedy bacterial wound infections owing to their versatile features. However, misuse of antibiotics has resulted in drug resistance, and it remains a significant challenge to achieve both high antibacterial efficiency and without causing bacterial resistance. Here, the ‘MOF-first’ strategy was adopted, the porphyrinic metal-organic frameworks nanoparticles (PCN−224 NPs) were pre-synthesized first, and then the composite antibacterial PCN−224 NPs @ poly (ε-caprolactone) (PM) NFMs were fabricated via a facile co-electrospinning technology. This strategy allows large amounts of effective MOFs to be integrated into nanofibers to effectively eliminate bacteria without bacterial resistance and to realize a relatively fast production rate. Upon visible light (630 nm) irradiation for 30 min, the PM−25 NFMs have the best ¹O₂ generation performance, triggering remarkable photodynamic antibacterial effects against both S. aureus, MRSA, and E. coli bacteria with survival rates of 0.13%, 1.91%, and 2.06% respectively. Considering the photodynamic antibacterial performance of the composite nanofibrous membranes functionalized by porphyrinic MOFs, this simple approach may provide a feasible way to use MOF materials and biological materials to construct wound dressing with the versatility to serve as an antibacterial strategy in order to prevent bacterial resistance.

Two-Sided Antibacterial Cellulose Combining Probiotics and Silver Nanoparticles

The constant increase of antibiotic-resistant bacteria demands the design of novel antibiotic-free materials. The combination of antibacterials in a biocompatible biomaterial is a very promising strategy to treat infections caused by a broader spectrum of resistant pathogens. Here, we combined two antibacterials, silver nanoparticles (AgNPs) and living probiotics (Lactobacillus fermentum, Lf), using bacterial cellulose (BC) as scaffold. By controlling the loading of each antibacterial at opposite BC sides, we obtained a two-sided biomaterial (AgNP-BC-Lf) with a high density of alive and metabolically active probiotics on one surface and AgNPs on the opposite one, being probiotics well preserved from the killer effect of AgNPs. The resulting two-sided biomaterial was characterized by Field-Emission Scanning Electron Microscopy (FESEM) and Confocal Laser Scanning Microscopy (CLSM). The antibacterial capacity against Pseudomonas aeruginosa (PA), an opportunistic pathogen responsible for a broad range of skin infections, was also assessed by agar diffusion tests in pathogen-favorable media. Results showed an enhanced activity against PA when both antibacterials were combined into BC (AgNP-BC-Lf) with respect to BC containing only one of the antibacterials, BC-Lf or AgNP-BC. Therefore, AgNP-BC-Lf is an antibiotic-free biomaterial that can be useful for the therapy of topical bacterial infections.