Photothermal-assisted antibacterial application of graphene oxide-Ag nanocomposites against clinically isolated multi-drug resistant Escherichia coli

Designing Composite Stimuli-Responsive Hydrogels for Wound Healing Applications: The State-of-the-Art and Recent Discoveries

Effective wound treatment has become one of the most important challenges for healthcare as it continues to be one of the leading causes of death worldwide. Therefore, wound care technologies significantly evolved in order to provide a holistic approach based on various designs of functional wound dressings. Among them, hydrogels have been widely used for wound treatment due to their biocompatibility and similarity to the extracellular matrix. The hydrogel formula offers the control of an optimal wound moisture level due to its ability to absorb excess fluid from the wound or release moisture as needed. Additionally, hydrogels can be successfully integrated with a plethora of biologically active components (e.g., nanoparticles, pharmaceuticals, natural extracts, peptides), thus enhancing the performance of resulting composite hydrogels in wound healing applications. In this review, the-state-of-the-art discoveries related to stimuli-responsive hydrogel-based dressings have been summarized, taking into account their antimicrobial, anti-inflammatory, antioxidant, and hemostatic properties, as well as other effects (e.g., re-epithelialization, vascularization, and restoration of the tissue) resulting from their use.

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.

Graphene in nanomedicine: A review on nano-bio factors and antibacterial activity

Graphene-based nanomaterials possess potent antibacterial activity and have engrossed immense interest among researchers as an active armour against pathogenic microbes. A comprehensive perception of the antibacterial activity of these nanomaterials is critical to the fabrication of highly effective antimicrobial nanomaterials, which results in highly efficient and enhanced activity. These materials owing to their antimicrobial activity are utilized as nanomedicine against various pathogenic microbes. The present article reviews the antimicrobial activity of graphene and its analogs such as graphene oxide, reduced graphene oxide as well as metal, metal oxide and polymeric composites. The review draws emphasis on the effect of various nano-bio factors on the antibacterial capability. It also provides an insight into the antibacterial properties of these materials along with a brief discussion on the discrepancies in their activities as evidenced by the scientific communities. In this way, the review is expected to shed light on future research and development in graphene-based nanomedicine.

An indolizine squaraine-based water-soluble NIR dye for fluorescence imaging of multidrug-resistant bacteria and antibacterial/antibiofilm activity using the photothermal effect

The majority of nosocomial infections are caused by bacteria with antimicrobial resistance and the formation of biofilms, such as implant-related bacterial infections and sepsis. There is an urgent need to develop new strategies for early-stage screening, destruction of multidrug-resistant bacteria, and efficient inhibition of biofilms. Organic dyes that absorb and emit in the near-infrared (NIR) region are potentially non-invasive, high-resolution, and rapid biological imaging materials. In this study, a non-toxic and biocompatible indolizine squaraine dye with water-solubilizing sulfonate groups (SO₃SQ) is studied for bacterial imaging and photothermal therapy (PTT). PTT is efficient in eliminating microorganisms through local hyperthermia without the risk of developing drug-resistant bacteria. The optical properties of SO₃SQ are studied extensively in phosphate-buffered saline (PBS). UV-Vis-NIR absorption spectra analysis shows a strong absorption between 650 nm - 1000 nm. SO₃SQ allows for the wash-free fluorescence imaging of drug-resistant bacteria via NIR fluorescence imaging due to a "turn-on" fluorescence property of the dye when interacting with bacteria. Although SO₃SQ exhibits no toxicity against both Gram-positive bacteria and Gram-negative bacteria, the PTT property of SO₃SQ is efficient in killing bacteria as well as inhibiting and eradicating biofilms. PTT experiments demonstrate that SO₃SQ reduces 90% of cell viability in bacterial strains under NIR radiation with a minimum inhibition concentration (MIC₉₀) of >450 μg/mL. The PTT property of SO₃SQ can also inhibit biofilms (BIC₉₀ = 1000-2000 μg/mL) and eradicate both preformed young and mature biofilms (MBEC₉₀ = 1500-2000 μg/mL) as observed by crystal violet assays.

Nanomaterials-Based Wound Dressing for Advanced Management of Infected Wound

The effective prevention and treatment of bacterial infections is imperative to wound repair and the improvement of patient outcomes. In recent years, nanomaterials have been extensively applied in infection control and wound healing due to their special physiochemical and biological properties. Incorporating antibacterial nanomaterials into wound dressing has been associated with improved biosafety and enhanced treatment outcomes compared to naked nanomaterials. In this review, we discuss progress in the application of nanomaterial-based wound dressings for advanced management of infected wounds. Focus is given to antibacterial therapy as well as the all-in-one detection and treatment of bacterial infections. Notably, we highlight progress in the use of nanoparticles with intrinsic antibacterial performances, such as metals and metal oxide nanoparticles that are capable of killing bacteria and reducing the drug-resistance of bacteria through multiple antimicrobial mechanisms. In addition, we discuss nanomaterials that have been proven to be ideal drug carriers for the delivery and release of antimicrobials either in passive or in stimuli-responsive manners. Focus is given to nanomaterials with the ability to kill bacteria based on the photo-triggered heat (photothermal therapy) or ROS (photodynamic therapy), due to their unparalleled advantages in infection control. Moreover, we highlight examples of intelligent nanomaterial-based wound dressings that can detect bacterial infections in-situ while providing timely antibacterial therapy for enhanced management of infected wounds. Finally, we highlight challenges associated with the current nanomaterial-based wound dressings and provide further perspectives for future improvement of wound healing.

The inhibitory effect of some pyrazole ligands and their Cu(II) complexes on the growth of Escherichia coli, Klebsiella–Enterobacter spp., and Staphylococcus aureus

The aim of this study was to evaluate the inhibitory activity of chemistry products against the growth of Escherichia coli, Klebsiella–Enterobacter spp., and Staphylococcus aureus. Pyrazole derivatives (4-bromo-2-(1H-pyrazol-3-yl)phenol, 4-nitro-3-pyrazolecarboxylic acid, N-(benzyloxycarbonyl)-1H-pyrazole-1-carboxamidine), 3-amino-5-hydroxypyrazole, 3,5-pyrazoledicarboxylic acid monohydrate, and selected complexes of Cu(II) with the mentioned pyrazoles as ligands were used as chemistry bioactives for antibacterial activity. The testing method was carried out according to the disc diffusion method. Some compounds have shown inhibitory effects against the growth of E. coli. A small number of compounds have shown inhibitory effects against the growth of Klebsiella–Enterobacter spp. but did not show inhibitory effects on Staphylococcus aureus compared to amoxicillin as a standard.

Multifarious global flora fabricated phytosynthesis of silver nanoparticles: a green nanoweapon for antiviral approach including SARS-CoV-2

The progressive research into the nanoscale level upgrades the higher end modernized evolution with every field of science, engineering, and technology. Silver nanoparticles and their broader range of application from nanoelectronics to nano-drug delivery systems drive the futuristic direction of nanoengineering and technology in contemporary days. In this review, the green synthesis of silver nanoparticles is the cornerstone of interest over physical and chemical methods owing to its remarkable biocompatibility and idiosyncratic property engineering. The abundant primary and secondary plant metabolites collectively as multifarious phytochemicals which are more peculiar in the composition from root hair to aerial apex through various interspecies and intraspecies, capable of reduction, and capping with the synthesis of silver nanoparticles. Furthermore, the process by which intracellular, extracellular biological macromolecules of the microbiota reduce with the synthesis of silver nanoparticles from the precursor molecule is also discussed. Viruses are one of the predominant infectious agents that gets faster resistance to the antiviral therapies of traditional generations of medicine. We discuss the various stages of virus targeting of cells and viral target through drugs. Antiviral potential of silver nanoparticles against different classes and families of the past and their considerable candidate for up-to-the-minute need of complete addressing of the fulminant and opportunistic global pandemic of this millennium SARS-CoV2, illustrated through recent silver-based formulations under development and approval for countering the pandemic situation.

Graphical abstract

Nanotechnology: A Potential Weapon to Fight against COVID-19

The COVID-19 infections have posed an unprecedented global health emergency, with nearly three million deaths to date, and have caused substantial economic loss globally. Hence, an urgent exploration of effective and safe diagnostic/therapeutic approaches for minimizing the threat of this highly pathogenic coronavirus infection is needed. As an alternative to conventional diagnosis and antiviral agents, nanomaterials have a great potential to cope with the current or even future health emergency situation with a wide range of applications. Fundamentally, nanomaterials are physically and chemically tunable and can be employed for the next generation nanomaterial-based detection of viral antigens and host antibodies in body fluids as antiviral agents, nanovaccine, suppressant of cytokine storm, nanocarrier for efficient delivery of antiviral drugs at infection site or inside the host cells, and can also be a significant tool for better understanding of the gut microbiome and SARS-CoV-2 interaction. The applicability of nanomaterial-based therapeutic options to cope with the current and possible future pandemic is discussed here.

The effects of bimodal action of photodynamic and photothermal therapy on antimicrobial and shear bond strength properties of orthodontic composite containing nano-graphene oxide

BACKGROUND

White spot lesions are a common adverse effect of fixed orthodontic treatment and represent the main challenge to achieving esthetic appearance. The purpose of the current study was to evaluate physico-mechanical and antimicrobial potency of orthodontic composite (OC; Transbond XT) containing nano-structured graphene oxide (nGO) (OC-nGO) as a novel composite following photodynamic therapy (PDT) and photothermal therapy (PTT) against Streptococcus mutans.

MATERIALS AND METHODS

Following preparation of OC-nGO, shear bond strength (SBS) and adhesive remnant index (ARI) of the test OC-nGO (containing 1, 2, 5, and 10% wt. nGO) were measured using a universal testing machine and stereomicroscope, respectively. The antimicrobial activities of test OC contained different concentrations of nGO were determined by disk agar diffusion (DAD), biofilm formation inhibition, and eluted components assays. After continuously rinsed in the aging process (up to 180 days), the antimicrobial activity of OC-nGO containing the highest concentration of nGO which had simultaneously the highest antimicrobial activity and SBS value were determined by DAD, biofilm formation, metabolic activity, and gtfB gene expression assays following photo-activation using diode laser irradiation against S. mutans. Data were analyzed using One-way Analysis of Variance (ANOVA). The Bonferroni post hoc test was used for comparison between the experimental groups. The significant difference was considered at P values < 0.05.

RESULTS

OC with 5% wt. nGO showed simultaneously the highest SBS value (10.64 ± 2.76 MPa, P < 0.05) an antimicrobial and anti-biofilm activities. The OC-nGO in all test concentrations of nGO had ARI scores as same as control group (Transbond XT without the nGO) (P < 0.05). In microbial biofilm formation and gene expression assays, the reduction of photothermal disinfection and anti-virulence activities of the 5% wt. OC-nGO against test bacterium was associated with the time of aging process, so they were reduced significantly up to day 150. Diode laser irradiated 5% wt. OC-nGO suppressed 15.6 and 8.1-fold gtfB mRNA expressions in the biofilm growth of the S. mutans at days 120 and 150 of rinsing (P < 0.05). Microbial biofilm formation and gtfB gene expression in S. mutans at day 180 following PAD had a high level of similarity with OOC as the control group. 5% wt. OC-nGO following photo-activation was not colonized by the S. mutans at day 90 and significant suppressed 91.98% and 76.37% of S. mutans biofilm formation at day 120 and 150, respectively (both P < 0.05). From day 120 onwards, metabolic activity was progressively increased on laser-irradiated 5% wt. OC-nGO discs compared to the control group (OC alone). Photo-activated OC-nGO containing 5% wt. nGO suppressed 86.94% and 46.82% metabolic activity of the S. mutans at days 120 and 150 of rinsing (both P < 0.05).

CONCLUSIONS

Our data support that the photo-activated 5% wt. OC-nGO can serve as an orthodontic composite/adhesive additive to control cariogenic bacterial biofilms.

Antiviral performance of graphene-based materials with emphasis on COVID-19: A review

Coronavirus disease-2019 has been one of the most challenging global epidemics of modern times with a large number of casualties combined with economic hardships across the world. Considering that there is still no definitive cure for the recent viral crisis, this article provides a review of nanomaterials with antiviral activity, with an emphasis on graphene and its derivatives, including graphene oxide, reduced graphene oxide and graphene quantum dots. The possible interactions between surfaces of such nanostructured materials with coronaviruses are discussed. The antiviral mechanisms of graphene materials can be related to events such as the inactivation of virus and/or the host cell receptor, electrostatic trapping and physico-chemical destruction of viral species. These effects can be enhanced by functionalization and/or decoration of carbons with species that enhances graphene-virus interactions. The low-cost and large-scale preparation of graphene materials with enhanced antiviral performances is an interesting research direction to be explored.

Gold nanoclusters exert antibacterial effects against gram-negative bacteria by targeting thiol-redox homeostasis

Low-molecular-weight thiols play a central role in preventing oxidative damage caused by reactive oxygen species to maintain a reductive intracellular environment in bacteria. Therefore, targeting thiol-redox homeostasis is considered a promising antimicrobial strategy. Here, we synthesize histidine-stabilized gold nanoclusters (Au NCs), in which the histidine ligand has a weak affinity for gold, thus constructing an effective thiol scavenger by employing metal-thiol depletion chemicals. Au NCs exert excellent antimicrobial effects by consuming thiols and simultaneously causing the accumulation of reactive oxygen species in bacteria, resulting in severe oxidative stress. In a mouse skin wound model infected with ampicillin-resistant Escherichia coli pHSP70-EGFP, a low dose of Au NCs exerts a strong therapeutic effect on bacterial clearance and wound healing, indicating the effectiveness of this antimicrobial strategy for clinical application.