Antimicrobial Photothermal Treatment of Pseudomonas Aeruginosa by a Carbon Nanoparticles-Polypyrrole Nanocomposite

Ultrathin TiS2@N,S-Doped Carbon Hybrid Nanosheets as Highly Efficient Photoresponsive Antibacterial Agents

Nanobactericides are employed as a promising class of nanomaterials for eradicating microbial infections, considering the rapid resistance risks of conventional antibiotics. Herein, we present a pioneering approach, reporting the synthesis of two-dimensional titanium disulfide nanosheets coated by nitrogen/sulfur-codoped carbon nanosheets (2D-TiS2@NSCLAA hybrid NSs) using a rapid l-ascorbic acid-assisted sulfurization of Ti3C2Tx-MXene to achieve efficient alternative bactericides. The as-developed materials were systematically characterized using a suite of different spectroscopy and microscopy techniques, in which the X-ray diffraction/Raman spectroscopy/X-ray photoelectron spectroscopy data confirm the existence of TiS2 and C, while the morphological investigation reveals single- to few-layered TiS2 NSs confined by N,S-doped C, suggesting the successful synthesis of the ultrathin hybrid NSs. From in vitro evaluation, the resultant product demonstrates impressive bactericidal potential against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria, achieving a substantial decrease in the bacterial viability under a 1.2 J dose of visible-light irradiation at the lowest concentration of 5 μg·mL-1 compared to Ti3C2Tx (15 μg·mL-1), TiS2-C (10 μg·mL-1), and standard antibiotic ciprofloxacin (15 μg·mL-1), respectively. The enhanced degradation efficiency is attributed to the ultrathin TiS2 NSs encapsulated within heteroatom N,S-doped C, facilitating effective photogenerated charge-carrier separation that generates multiple reactive oxygen species (ROS) and induced physical stress as well as piercing action due to its ultrathin structure, resulting in multimechanistic cytotoxicity and damage to bacterial cells. Furthermore, the obtained results from molecular docking studies conducted via computational simulation (in silico) of the as-synthesized materials against selected proteins (β-lactamasE. coli/DNA-GyrasE. coli) are well-consistent with the in vitro antibacterial results, providing strong and consistent validation. Thus, this sophisticated study presents a simple and effective synthesis technique for the structural engineering of metal sulfide-based hybrids as functionalized synthetic bactericides.

Immune homeostasis modulation by hydrogel-guided delivery systems: a tool for accelerated bone regeneration

Immune homeostasis is delicately mediated by the dynamic balance between effector immune cells and regulatory immune cells. Local deviations from immune homeostasis in the microenvironment of bone fractures, caused by an increased ratio of effector to regulatory cues, can lead to excessive inflammatory conditions and hinder bone regeneration. Therefore, achieving effective and localized immunomodulation of bone fractures is crucial for successful bone regeneration. Recent research has focused on developing localized and specific immunomodulatory strategies using local hydrogel-based delivery systems. In this review, we aim to emphasize the significant role of immune homeostasis in bone regeneration, explore local hydrogel-based delivery systems, discuss emerging trends in immunomodulation for enhancing bone regeneration, and address the limitations of current delivery strategies along with the challenges of clinical translation.

Metal-coordination synthesis of a natural injectable photoactive hydrogel with antibacterial and blood-aggregating functions for cancer thermotherapy and mild-heating wound repair

Photothermal therapy (PTT) is a promising approach for treating cancer. However, it suffers from the formation of local lesions and subsequent bacterial infection in the damaged area. To overcome these challenges, the strategy of mild PTT following the high-temperature ablation of tumors is studied to achieve combined tumor suppression, wound healing, and bacterial eradication using a hydrogel. Herein, Bi₂S₃ nanorods (NRs) are employed as a photothermal agent and coated with hyaluronic acid to obtain BiH NRs with high colloidal stability. These NRs and allantoin are loaded into an injectable Fe³⁺-coordinated hydrogel composed of sodium alginate (Alg) and Farsi gum (FG), which is extracted from Amygdalus scoparia Spach. The hydrogel can be used for localized cancer therapy by high-temperature PTT, followed by wound repair through the combination of mild hyperthermia and allantoin-mediated induction of cell proliferation. In addition, an outstanding blood clotting effect is observed due to the water-absorbing ability and negative charge of FG and Alg as well as the porous structure of hydrogels. The hydrogels also eradicate infection owing to the local heat generation and intrinsic antimicrobial activity of the NRs. Lastly, in vivo studies reveal an efficient photothermal-based tumor eradication and accelerated wound healing by the hydrogel.

Sweet light o' mine: Photothermal and photodynamic inactivation of tenacious pathogens using conjugated polymers

Each year a rising number of infections can not be successfully treated owing to the increasing pandemic of antibiotic resistant pathogens. The global shortage of innovative antibiotics fuels the emergence and spread of drug resistant microbes. Basic research, development, and applications of alternative therapies are urgently needed. Since the 90´s, light-mediated therapies have promised to be the next frontier combating multidrug-resistance microbes. These platforms have demonstrated to be a reliable, rapid, and efficient alternative to eliminate tenacious pathogens while avoiding the emergence of resistance mechanisms. Among the materials showing antimicrobial activity triggered by light, conjugated polymers (CPs) have risen as the most promising option to tackle this complex situation. These materials present outstanding characteristics such as high absorption coefficients, great photostability, easy processability, low cytotoxicity, among others, turning them into a powerful class of photosensitizer (PS)/photothermal agent (PTA) materials. Herein, we summarize and discuss the advances in the field of CPs with applications in photodynamic inactivation and photothermal therapy towards bacteria elimination. Additionally, a section of current challenges and needs in terms of well-defined benchmark experiments and conditions to evaluate the efficiency of phototherapies is presented.

Design, Synthesis, and Application of Carbon Dots With Synergistic Antibacterial Activity

The diversity of bacteria and their ability to acquire drug resistance lead to many challenges in traditional antibacterial methods. Photothermal therapies that convert light energy into localized physical heat to kill target microorganisms do not induce resistance and provide an alternative for antibacterial treatment. However, many photothermal materials cannot specifically target bacteria, which can lead to thermal damage to normal tissues, thus seriously affecting their biological applications. Here, we designed and synthesized bacteria-affinitive photothermal carbon dots (BAPTCDs) targeting MurD ligase that catalyzes the synthesis of peptidoglycan (PG) in bacteria. BAPTCDs presented specific recognition ability and excellent photothermal properties. BAPTCDs can bind to bacteria very tightly due to their chiral structure and inhibit enzyme activity by competing with D-glutamic acid to bind to MurD ligases, thus inhibiting the synthesis of bacterial walls. It also improves the accuracy of bacteria treatment by laser irradiation. Through the synergy of biochemical and physical effects, the material offers outstanding antibacterial effects and potentially contributes to tackling the spread of antibiotic resistance and facilitation of antibiotic stewardship.

Nanotechnology-based combinatorial phototherapy for enhanced cancer treatment

Nanotechnology-based phototherapy has attracted enormous attention to cancer treatment owning to its non-invasiveness, high controllability and accuracy. Given the fast development of anti-tumor strategies, we summarize various examples of multifunctional nanosystems to highlight the recent advances in nanotechnology-based combinatorial phototherapy towards improving cancer treatment. The limitations of the monotherapeutic approach and the superiority of the photo-involved combinatorial strategies are discussed in each part. The future breakthroughs and clinical perspectives of combinatorial phototherapy are also outlooked. Our perspectives may inspire researchers to develop more effective phototherapy-based cancer-treating approaches.

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.

Emerging Trends in Nanomaterials for Antibacterial Applications

Around the globe, surges of bacterial diseases are causing serious health threats and related concerns. Recently, the metal ion release and photodynamic and photothermal effects of nanomaterials were demonstrated to have substantial efficiency in eliminating resistance and surges of bacteria. Nanomaterials with characteristics such as surface plasmonic resonance, photocatalysis, structural complexities, and optical features have been utilized to control metal ion release, generate reactive oxygen species, and produce heat for antibacterial applications. The superior characteristics of nanomaterials present an opportunity to explore and enhance their antibacterial activities leading to clinical applications. In this review, we comprehensively list three different antibacterial mechanisms of metal ion release, photodynamic therapy, and photothermal therapy based on nanomaterials. These three different antibacterial mechanisms are divided into their respective subgroups in accordance with recent achievements, showcasing prospective challenges and opportunities in clinical, environmental, and related fields.

Pseudomonas aeruginosa Biofilms

Pseudomonas aeruginosa is an opportunistic human pathogen causing devastating acute and chronic infections in individuals with compromised immune systems. Its highly notorious persistence in clinical settings is attributed to its ability to form antibiotic-resistant biofilms. Biofilm is an architecture built mostly by autogenic extracellular polymeric substances which function as a scaffold to encase the bacteria together on surfaces, and to protect them from environmental stresses, impedes phagocytosis and thereby conferring the capacity for colonization and long-term persistence. Here we review the current knowledge on P. aeruginosa biofilms, its development stages, and molecular mechanisms of invasion and persistence conferred by biofilms. Explosive cell lysis within bacterial biofilm to produce essential communal materials, and interspecies biofilms of P. aeruginosa and commensal Streptococcus which impedes P. aeruginosa virulence and possibly improves disease conditions will also be discussed. Recent research on diagnostics of P. aeruginosa infections will be investigated. Finally, therapeutic strategies for the treatment of P. aeruginosa biofilms along with their advantages and limitations will be compiled.