A multifunctional platform with single-NIR-laser-triggered photothermal and NO release for synergistic therapy against multidrug-resistant Gram-negative bacteria and their biofilms

Acidic biofilm microenvironment-responsive ROS generation via a protein nanoassembly with hypoxia-relieving and GSH-depleting capabilities for efficient elimination of biofilm bacteria

Reactive oxygen species (ROS) are widely considered to the effective therapeutics for fighting bacterial infections especially those associated with biofilm. However, biofilm microenvironments including hypoxia, limited H2O2, and high glutathione (GSH) level seriously limit the therapeutic efficacy of ROS-based strategies. Herein, we have developed an acidic biofilm microenvironment-responsive antibacterial nanoplatform consisting of copper-dopped bovine serum albumin (CBSA) loaded with copper peroxide (CuO2) synthesized in situ and indocyanine green (ICG). The three-in-one nanotherapeutics (CuO2/ICG@CBSA) are capable of releasing Cu2+ and H2O2 in a slightly acidic environment, where Cu2+ catalyzes the conversion of H2O2 into hydroxyl radical (•OH) and consumes the highly expressed GSH to disrupt the redox homeostasis. With the assistance of an 808 nm laser, the loaded ICG not only triggers the production of singlet oxygen (1O2) by a photodynamic process, but also provides photonic hyperpyrexia that further promotes the Fenton-like reaction for enhancing •OH production and induces thermal decomposition of CuO2 for the O2-self-supplying 1O2 generation. The CuO2/ICG@CBSA with laser irradiation demonstrates photothermal-augmented multi-mode synergistic bactericidal effect and is capable of inhibiting biofilm formation and eradicating the biofilm bacteria. Further in vivo experiments suggest that the CuO2/ICG@CBSA can effectively eliminate wound infections and accelerate wound healing. The proposed three-in-one nanotherapeutics with O2/H2O2-self-supplied ROS generating capability show great potential in treating biofilm-associated bacterial infections. STATEMENT OF SIGNIFICANCE: Here, we have developed an acidic biofilm microenvironment-responsive nanoplatform consisting of copper-dopped bovine serum albumin (CBSA) loaded with copper peroxide (CuO2) synthesized in situ and indocyanine green (ICG). The nanotherapeutics (CuO2/ICG@CBSA) are capable of releasing Cu2+ and H2O2 in an acidic environment, where Cu2+ catalyzes the conversion of H2O2 into •OH and consumes the overexpressed GSH to improve oxidative stress. With the aid of an 808 nm laser, ICG provides photonic hyperpyrexia for enhancing •OH production, and triggers O2-self-supplying 1O2 generation. CuO2/ICG@CBSA with laser irradiation displays photothermal-augmented multi-mode antibacterial and antibiofilm effect. Further in vivo experiments prove that CuO2/ICG@CBSA effectively eliminates wound infection and promotes wound healing. The proposed three-in-one nanotherapeutics show great potential in treating biofilm-associated bacterial infections.

A novel exosome-based multifunctional nanocomposite platform driven by photothermal-controlled release system for repair of skin injury

Currently, exosomes showed appropriate potential in the repair of skin injury. However, the functions of the exosomes could be compromised rapidly due to their short half-life and high clearance rate in vivo. In addition, the controlled release of effective concentrations of exosomes could increase the utilization efficiency of exosomes in wound healing. Accordingly, the design of an effective system for the controlled delivery of exosomes during the wound treatment period was necessary. In this contribution, we designed a novel exosome-based multifunctional nanocomposite platform with photothermal-controlled release performance for the repair of skin injury. Based on the agarose hydrogel, two-dimensional Ti3C2 (Ti3C2 MXene) and human umbilical cord mesenchymal stem cell (hucMSC)-derived exosomes, the as-prepared platform (i.e., hucMSC-derived exosome/Ti3C2 MXene hydrogel) was synthesized for the first time. Apart from possessing injectability, the hucMSC-derived exosome/Ti3C2 MXene hydrogel utilized the excellent photothermal effect of Ti3C2 MXene and proper phase transition performance of agarose hydrogel to provide a photothermal-controlled release system for the hucMSC-derived exosomes, which was beneficial for the personalized on-demand drug delivery. Importantly, the hucMSC-derived exosomes maintained their inherent structure and activity after being released from the Ti3C2 MXene hydrogel. Additionally, the as-prepared hydrogel with multifunctional performance also presented remarkable biocompatibility and photothermal-antibacterial property, and could efficiently accelerate wound healing by promoting cell proliferation, angiogenesis, collagen deposition, and reducing the level of inflammation at the wound site. The results suggested that the exosome-based multifunctional nanocomposite platform with great potential for wound healing would make significant advances in the revolution of traditional treatment methods in skin injury.

Healing with precision: A multi-functional hydrogel-bioactive glass dressing boosts infected wound recovery and enhances neurogenesis in the wound bed

Chronic skin wounds, especially infected ones, pose a significant clinical challenge due to their increasing incidence and poor outcomes. The deteriorative microenvironment in such wounds, characterized by reduced extracellular matrix, impaired angiogenesis, insufficient neurogenesis, and persistent bacterial infection, has prompted the exploration of novel therapeutic strategies. In this study, we developed an injectable multifunctional hydrogel (GEL/BG@Cu + Mg) incorporating Gelatin-Tannic acid/ N-hydroxysuccinimide functionalized polyethylene glycol and Bioactive glass doped with copper and magnesium ions to accelerate the healing of infected wounds. The GEL/BG@Cu + Mg hydrogel composite demonstrates good biocompatibility, degradability, and rapid formation of a protective barrier to stop bleeding. Synergistic bactericidal effects are achieved through the photothermal properties of BG@Cu + Mg and sustained copper ions release, with the latter further promoting angiogenesis. Furthermore, the hydrogel enhances neurogenesis by stimulating axons and Schwann cells in the wound bed through the beneficial effects of magnesium ions. Our results demonstrate that the designed novel multifunctional hydrogel holds tremendous promise for treating infected wounds and allowing regenerative neurogenesis at the wound site, which provides a viable alternative for further improving clinical outcomes.

Nanomaterials Regulate Bacterial Quorum Sensing: Applications, Mechanisms, and Optimization Strategies

Anti-virulence therapy that interferes with bacterial communication, known as "quorum sensing (QS)", is a promising strategy for circumventing bacterial resistance. Using nanomaterials to regulate bacterial QS in anti-virulence therapy has attracted much attention, which is mainly attributed to unique physicochemical properties and excellent designability of nanomaterials. However, bacterial QS is a dynamic and multistep process, and there are significant differences in the specific regulatory mechanisms and related influencing factors of nanomaterials in different steps of the QS process. An in-depth understanding of the specific regulatory mechanisms and related influencing factors of nanomaterials in each step can significantly optimize QS regulatory activity and enhance the development of novel nanomaterials with better comprehensive performance. Therefore, this review focuses on the mechanisms by which nanomaterials regulate bacterial QS in the signal supply (including signal synthesis, secretion, and accumulation) and signal transduction cascade (including signal perception and response) processes. Moreover, based on the two key influencing factors (i.e., the nanomaterial itself and the environment), optimization strategies to enhance the QS regulatory activity are comprehensively summarized. Collectively, applying nanomaterials to regulate bacterial QS is a promising strategy for anti-virulence therapy. This review provides reference and inspiration for further research on the anti-virulence application of nanomaterials.

Photothermal synergistic nitric oxide controlled release injectable self-healing adhesive hydrogel for biofilm eradication and wound healing

The development of injectable self-healing adhesive hydrogel dressings with excellent bactericidal activity and wound healing ability is urgently in demand for combating biofilm infections. Herein, a multifunctional hydrogel (QP/QT-MB) with near-infrared (NIR) light-activated mild photothermal/gaseous antimicrobial activity was developed based on the dynamic reversible borate bonds and hydrogen bonds crosslinking between quaternization chitosan (QCS) derivatives alternatively containing phenylboronic acid and catechol-like moieties in conjunction with the in situ encapsulation of BNN6-loaded mesoporous polydopamine (MPDA@BNN6 NPs). Given the dynamic reversible cross-linking feature, the versatile hybrid hydrogel exhibited injectability, flexibility, and rapid self-healing ability. The numerous phenylboronic acid and catechol-like moieties on the QCS backbone confer the hydrogel with specific bacterial affinity, desirable tissue adhesion, and antioxidant stress ability that enhance bactericidal activity and facilitate the regeneration of infection wounds. Under NIR irradiation, the QP/QT-MB hydrogels exhibited a desirable mild photothermal effect and NIR-activity controllable NO delivery, combined with the endogenous contact antimicrobial activity of hydrogel, contributing jointly to induce dispersal of biofilms and disruption of the bacterial plasma membranes, ultimately leading to bacteria inactivation and biofilm elimination. In vivo experiments demonstrated that the fabricated QP/QT-MB hydrogel platform was capable of inducing efficient eradication of the S. aureus biofilm in a severely infected wound model and accelerating infected wound repair by promoting collagen deposition, angiogenesis, and suppressing inflammatory responses. Additionally, the QP/QT-MB hydrogel demonstrated excellent biocompatibility in vitro and in vivo. Collectively, the hydrogel (QP/QT-MB) reveals great potential application prospects as a promising alternative in the field of biofilm-associated infection treatment.

A photoactivatable and phenylboronic acid-functionalized nanoassembly for combating multidrug-resistant gram-negative bacteria and their biofilms

Background

Multidrug-resistant (MDR) gram-negative bacteria-related infectious diseases have caused an increase in the public health burden and mortality. Moreover, the formation of biofilms makes these bacteria difficult to control. Therefore, developing novel interventions to combat MDR gram-negative bacteria and their biofilms-related infections are urgently needed. The purpose of this study was to develop a multifunctional nanoassembly (IRNB) based on IR-780 and N, N'-di-sec-butyl-N, N'- dinitroso-1,4-phenylenediamine (BNN6) for synergistic effect on the infected wounds and subcutaneous abscesses caused by gram-negative bacteria.

Methods

The characterization and bacteria-targeting ability of IRNB were investigated. The bactericidal efficacy of IRNB against gram-negative bacteria and their biofilms was demonstrated by crystal violet staining assay, plate counting method and live/dead staining in vitro. The antibacterial efficiency of IRNB was examined on a subcutaneous abscess and cutaneous infected wound model in vivo. A cell counting kit-8 assay, Calcein/PI cytotoxicity assay, hemolysis assay and intravenous injection assay were performed to detect the biocompatibility of IRNB in vitro and in vivo.

Results

Herein, we successfully developed a multifunctional nanoassembly IRNB based on IR-780 and BNN6 for synergistic photothermal therapy (PTT), photodynamic therapy (PDT) and nitric oxide (NO) effect triggered by an 808 nm laser. This nanoassembly could accumulate specifically at the infected sites of MDR gram-negative bacteria and their biofilms via the covalent coupling effect. Upon irradiation with an 808 nm laser, IRNB was activated and produced both reactive oxygen species (ROS) and hyperthermia. The local hyperthermia could induce NO generation, which further reacted with ROS to generate ONOO-, leading to the enhancement of bactericidal efficacy. Furthermore, NO and ONOO- could disrupt the cell membrane, which converts bacteria to an extremely susceptible state and further enhances the photothermal effect. In this study, IRNB showed a superior photothermal-photodynamic-chemo (NO) synergistic therapeutic effect on the infected wounds and subcutaneous abscesses caused by gram-negative bacteria. This resulted in effective control of associated infections, relief of inflammation, promotion of re-epithelization and collagen deposition, and regulation of angiogenesis during wound healing. Moreover, IRNB exhibited excellent biocompatibility, both in vitro and in vivo.

Conclusions

The present research suggests that IRNB can be considered a promising alternative for treating infections caused by MDR gram-negative bacteria and their biofilms.

Recent advances in nanomaterial-mediated bacterial molecular action and their applications in wound therapy

Because of the multi-pathway antibacterial mechanisms of nanomaterials, they have received widespread attention in wound therapy. However, owing to the complexities of bacterial responses toward nanomaterials, antibacterial molecular mechanisms remain unclear, making it difficult to rationally design highly efficient antibacterial nanomaterials. Fortunately, molecular dynamics simulations and omics techniques have been used as effective methods to further investigate the action targets of nanomaterials. Therefore, the review comprehensively analyzes the antibacterial mechanisms of nanomaterials from the morphology-dependent antibacterial activity and physicochemical/optical properties-dependent antibacterial activity, which provided guidance for constructing excellently efficient and broad-spectrum antibacterial nanomaterials for wound therapy. More importantly, the main molecular action targets of nanomaterials from the membranes, DNA, energy metabolism pathways, oxidative stress defense systems, ribosomes, and biofilms are elaborated in detail. Furthermore, nanomaterials used in wound therapy are reviewed and discussed. Finally, future directions of nanomaterials from mechanisms to nanomedicine are further proposed.

Surface charge adaptive nitric oxide nanogenerator for enhanced photothermal eradication of drug-resistant biofilm infections

Due to protection of extracellular polymeric substances, the therapeutic efficiency of conventional antimicrobial agents is often impeded by their poor infiltration and accumulation in biofilm. Herein, one type of surface charge adaptable nitric oxide (NO) nanogenerator was developed for biofilm permeation, retention and eradication. This nanogenerator (PDG@Au-NO/PBAM) is composed of a core-shell structure: thermo-sensitive NO donor conjugated AuNPs on cationic poly(dopamine-co-glucosamine) nanoparticle (PDG@Au-NO) served as core, and anionic phenylboronic acid-acryloylmorpholine (PBAM) copolymer was employed as a shell. The NO nanogenerator featured long circulation and good biocompatibility. Once the nanogenerator reached acidic biofilm, its surface charge would be switched to positive after shell dissociation and cationic core exposure, which was conducive for the nanogenerator to infiltrate and accumulate in the depth of biofilm. In addition, the nanogenerator could sustainably generate NO to disturb the integrity of biofilm at physiological temperature, then generate hyperthermia and explosive NO release upon NIR irradiation to efficiently eradicate drug-resistant bacteria biofilm. Such rational design offers a promising approach for developing nanosystems against biofilm-associated infections.

A pH/enzyme dual responsive PMB spatiotemporal release hydrogel promoting chronic wound repair

Suppressing persistent multidrug-resistant (MDR) bacterial infections and excessive inflammation is the key for treating chronic wounds. Therefore, developing a microenvironment-responsive material with good biodegradability, drug-loading, anti-infection, and anti-inflammatory properties is desired to boost the chronic wounds healing process; however, using ordinary assembly remains a defect. Herein, we propose a pH/enzyme dual-responsive polymyxin B (PMB) spatiotemporal-release hydrogel (GelMA/OSSA/PMB), namely, the amount of OSSA and PMB released from GelMA/OSSA/PMB was closely related the wound pH and the enzyme concentration changing. The GelMA/OSSA/PMB showed better biosafety than equivalent free PMB, owing to the controlled release of PMB, which helped kill planktonic bacteria and inhibit biofilm activity in vitro. In addition, the GelMA/OSSA/PMB exhibited excellent antibacterial and anti-inflammatory properties. A MDR Pseudomonas aeruginosa caused infection was effectively resolved by the GelMA/OSSA/PMB hydrogel in vivo, thereby significantly boosting wound closure during the inflammatory phase. Furthermore, GelMA/OSSA/PMB accelerated the sequential phases of wound repair.

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.

Advanced Nitric Oxide Generating Nanomedicine for Therapeutic Applications

Nitric oxide (NO), a gaseous transmitter extensively present in the human body, regulates vascular relaxation, immune response, inflammation, neurotransmission, and other crucial functions. Nitrite donors have been used clinically to treat angina, heart failure, pulmonary hypertension, and erectile dysfunction. Based on NO's vast biological functions, it further can treat tumors, bacteria/biofilms and other infections, wound healing, eye diseases, and osteoporosis. However, delivering NO is challenging due to uncontrolled blood circulation release and a half-life of under five seconds. With advanced biotechnology and the development of nanomedicine, NO donors packaged with multifunctional nanocarriers by physically embedding or chemically conjugating have been reported to show improved therapeutic efficacy and reduced side effects. Herein, we review and discuss recent applications of NO nanomedicines, their therapeutic mechanisms, and the challenges of NO nanomedicines for future scientific studies and clinical applications. As NO enables the inhibition of the replication of DNA and RNA in infectious microbes, including COVID-19 coronaviruses and malaria parasites, we highlight the potential of NO nanomedicines for antipandemic efforts. This review aims to provide deep insights and practical hints into design strategies and applications of NO nanomedicines.

A photoactive injectable antibacterial hydrogel to support chemo-immunotherapeutic effect of antigenic cell membrane and sorafenib by near-infrared light mediated tumor ablation

Intravenously administered nanocarriers suffer from off-target distribution, pre-targeting drug leakage, and rapid clearance, limiting their efficiency in tumor eradication. To bypass these challenges, an injectable hydrogel with time- and temperature-dependent viscosity enhancement behavior and self-healing property are reported to assist in the retention of the hydrogel in the tumor site after injection. The cancer cell membrane (CCM) and sorafenib are embedded into the hydrogel to elicit local tumor-specific immune responses and induce cancer cell apoptosis, respectively. In addition, hyaluronic acid (HA) coated Bi₂S₃ nanorods (BiH) are incorporated within the hydrogel to afford prolonged multi-cycle local photothermal therapy (PTT) due to the reduced diffusion of the nanorods to the surrounding tissues as a result of HA affinity toward cancer cells. The results show the promotion of immunostimulatory responses by both CCM and PTT through the release of inflammatory cytokines from immune cells, which allows localized and complete ablation of the breast tumor in an animal model by a single injection of the hydrogel. Moreover, the BiH renders strong antibacterial activity to the hydrogel, which is crucial for the clinical translation of injectable hydrogels as it minimizes the risk of infection in the post-cancer lesion formed by PTT-mediated cancer therapy.

Bilayer hydrogel dressing with lysozyme-enhanced photothermal therapy for biofilm eradication and accelerated chronic wound repair

Biofilms are closely associated with the tough healing and dysfunctional inflammation of chronic wounds. Photothermal therapy (PTT) emerged as a suitable alternative which could destroy the structure of biofilms with local physical heat. However, the efficacy of PTT is limited because the excessive hyperthermia could damage surrounding tissues. Besides, the difficult reserve and delivery of photothermal agents makes PTT hard to eradicate biofilms as expectation. Herein, we present a GelMA-EGF/Gelatin-MPDA-LZM bilayer hydrogel dressing to perform lysozyme-enhanced PTT for biofilms eradication and a further acceleration to the repair of chronic wounds. Gelatin was used as inner layer hydrogel to reserve lysozyme (LZM) loaded mesoporous polydopamine (MPDA) (MPDA-LZM) nanoparticles, which could rapidly liquefy while temperature rising so as to achieve a bulk release of nanoparticles. MPDA-LZM nanoparticles serve as photothermal agents with antibacterial capability, could deeply penetrate and destroy biofilms. In addition, the outer layer hydrogel consisted of gelatin methacryloyl (GelMA) and epidermal growth factor (EGF) promoted wound healing and tissue regeneration. It displayed remarkable efficacy on alleviating infection and accelerating wound healing in vivo. Overall, the innovative therapeutic strategy we came up with has significant effect on biofilms eradication and shows promising application in promoting the repair of clinical chronic wounds.

Nitric oxide-propelled nanomotors for bacterial biofilm elimination and endotoxin removal to treat infected burn wounds

Biofilm infection is regarded as a major contributing factor to the failure of burn treatment and a persistent inflammatory state delays healing and leads to the formation of chronic wounds. Herein, self-propelled nanomotors (NMs) are proposed to enhance biofilm infiltration, bacterial destruction, and endotoxin clearance to accelerate the healing of infected burn wounds. Janus nanoparticles (NPs) were prepared through partially coating Fe₃O₄ NPs with polydopamine (PDA) layers, and then polymyxin B (PMB) and thiolated nitric oxide (SNO) donors were separately grafted onto the Janus NPs to obtain IO@PMB-SNO NMs. In response to elevated glutathione (GSH) levels in biofilms, NO generation from one side of the Janus NPs leads to self-propelled motion and deep infiltration into biofilms. The local release of NO could destroy bacteria inside the biofilm, which provides a non-antibiotic antibiofilm approach without the development of drug resistance. In addition to intrinsic antibacterial effects, the PMB grafts preferentially bind with bacteria and the active motion enhances lipopolysaccharide (LPS) clearance and then significantly attenuates the production of inflammatory cytokines and reactive oxide species by macrophages. Partial-thickness burn wounds were established on mice and infected with P. aeruginosa, and NM treatment almost fully destroyed the bacteria in the wounds. IO@PMB-SNO NMs absorb LPS and remove it from the wounds under a magnetic field, which downregulates the interleukin-6 and tumor necrosis factor-α levels in tissues. The infected wounds were completely healed with the deposition and arrangement of collagen fibers and the generation of skin features similar to those of normal skin. Thus, IO@PMB-SNO NMs achieved multiple-mode effects, including GSH-triggered NO release and self-propelled motion, the NO-induced non-antibiotic elimination of biofilms and bacteria, and PMB-induced endotoxin removal. This study offers a feasible strategy, with integrated antibiofilm and anti-inflammatory effects, for accelerating the healing of infected burn wounds.

Advances and Potentials of Polydopamine Nanosystem in Photothermal-Based Antibacterial Infection Therapies

Bacterial infection remains one of the most dangerous threats to human health due to the increasing cases of bacterial resistance, which is caused by the extensive use of current antibiotics. Photothermal therapy (PTT) is similar to photodynamic therapy (PDT), but PTT can generate heat energy under the excitation of light of specific wavelength, resulting in overheating and damage to target cells or sites. Polydopamine (PDA) has been proved to show plenty of advantages, such as simple preparation, good photothermal conversion effects, high biocompatibility, and easy functionalization and adhesion. Taking these advantages, dopamine is widely used to synthesize the PDA nanosystem with excellent photothermal effects, good biocompatibility, and high drug loading ability, which therefore play more and more important roles for anticancer and antibacterial treatment. PDA nanosystem-mediated PTT has been reported to induce significant tumor inhibition, as well as bacterial killings due to PTT-induced hyperthermia. Moreover, combined with other cancer or bacterial inhibition strategies, PDA nanosystem-mediated PTT can achieve more effective tumor and bacterial inhibitions. In this review, we summarized the progress of preparation methods for the PDA nanosystem, followed by advances of their biological functions and mechanisms for PTT uses, especially in the field of antibacterial treatments. We also provided advances on how to combine PDA nanosystem-mediated PTT with other antibacterial methods for synergistic bacterial killings. Moreover, we further provide some prospects of PDA nanosystem-mediated PTT against intracellular bacteria, which might be helpful to facilitate their future research progress for antibacterial therapy.

pH-responsive hierarchical H2S-releasing nano-disinfectant with deep-penetrating and anti-inflammatory properties for synergistically enhanced eradication of bacterial biofilms and wound infection

Background

Methicillin-resistant Staphylococcus aureus (MRSA) biofilm-associated bacterial infection is the primary cause of nosocomial infection and has long been an ongoing threat to public health. MRSA biofilms are often resistant to multiple antimicrobial strategies, mainly due to the existence of a compact protective barrier; thus, protecting themselves from the innate immune system and antibiotic treatment via limited drug penetration.

Results

A hierarchically structured hydrogen sulfide (H₂S)-releasing nano-disinfectant was presented, which was composed of a zinc sulfide (ZnS) core as a H₂S generator and indocyanine green (ICG) as a photosensitizer. This nano-disinfectant (ICG-ZnS NPs) sensitively responded to the biofilm microenvironment and demonstrated efficient eradication of MRSA biofilms via a synergistic effect of Zn²⁺, gas molecule-mediated therapy, and hyperthermia. Physically boosted by released H₂S and a near-infrared spectroscopy-induced hyperthermia effect, ICG-ZnS NPs destroyed the compactness of MRSA biofilms showing remarkable deep-penetration capability. Moreover, on-site generation of H₂S gas adequately ameliorated excessive inflammation, suppressed secretion of inflammatory cytokines, and expedited angiogenesis, therefore markedly accelerating the in vivo healing process of cutaneous wounds infected with MRSA biofilms.

Conclusion

ICG-ZnS NPs combined with NIR laser irradiation exhibited significant anti-biofilm activity in MRSA biofilms, can accelerate the healing process through deep-penetration and anti-inflammatory effectuation. The proposed strategy has great potential as an alternative to antibiotic treatment when combating multidrug-resistant bacterial biofilms.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01262-7.

Nitric oxide-releasing micelles with intelligent targeting for enhanced anti-tumor effect of cisplatin in hypoxia

Background

Hypoxic tumor microenvironment (TME) promotes tumor metastasis and drug resistance, leading to low efficiency of cancer chemotherapy. The development of targeted agents or multi-target therapies regulating hypoxic microenvironment is an important approach to overcome drug resistance and metastasis.

Methods

In this study, chitosan oligosaccharide (COS)-coated and sialic acid (SA) receptor-targeted nano-micelles were prepared using film dispersion method to co-deliver cisplatin (CDDP) and nitric oxide (NO) (denoted as CTP/CDDP). In addition, we explored the mechanisms by which NO reversed CDDP resistance as well as enhanced anti-metastatic efficacy in hypoxic cancer cells.

Results

Because of the different affinities of COS and SA to phenylboronic acid (PBA) under different pH regimes, CTP/CDDP micelles with intelligent targeting property increased cellular uptake of CDDP and enhanced cytotoxicity to tumors, but reduced systemic toxicity to normal organs or tissues. In addition, CTP/CDDP showed stimulus-responsive release in TME. In terms of anti-tumor mechanism, CTP/CDDP reduced CDDP efflux and inhibited epithelial-mesenchymal transition (EMT) process of tumor by down-regulating hypoxia-inducible factor-1α (HIF-1α), glutathione (GSH), multidrug resistance-associated protein 2 (MRP2) and matrix metalloproteinase 9 (MMP9) expression, thus reversing drug resistance and metastasis of hypoxic tumor cells.

Conclusions

The designed micelles significantly enhanced anti-tumor effects both in vitro and in vivo. These results suggested that CTP/CDDP represented a promising strategy to treat resistance and metastatic tumors.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00989-z.

The recent progress in photothermal-triggered bacterial eradication

Increasing evidence suggested that bacterial infection diseases posed a great threat to human health and became the leading cause of mortality. However, the abuse of antibiotics and their residues in the environment result in the emergence and prevalence of drug-resistant bacteria. Photothermal therapy (PTT) has received considerable attention owing to its noninvasiveness, and proved to be promising in preventing bacterial infection diseases. In this review, we first surveyed the recent progress of PTT-based responsive targeting strategies for bacterial killing. We then highlighted the PTT-based smart designs of bio-films, hydrogels and synergistic methods for treating bacterial infections. Existing challenges and perspectives are also discussed to inspire the future development of a PTT-based platform for the efficient therapy of bacterial infections.

Emerging photothermal-derived multimodal synergistic therapy in combating bacterial infections

Due to the emerging bacterial resistance and the protection of tenacious biofilms, it is hard for the single antibacterial modality to achieve satisfactory therapeutic effects nowadays. In recent years, photothermal therapy (PTT)-derived multimodal synergistic treatments have received wide attention and exhibited cooperatively enhanced bactericidal activity. PTT features spatiotemporally controllable generation of hyperthermia that could eradicate bacteria without inducing resistance. The synergy of it with other treatments, such as chemotherapy, photo-dynamic/catalytic therapy (PDT/PCT), immunotherapy, and sonodynamic therapy (SDT), could lower the introduced laser density in PTT and avoid undesired overheating injury of normal tissues. Simultaneously, by heat-induced improvement of the bacterial membrane permeability, PTT is conducive for accelerated intracellular permeation of chemotherapeutic drugs as well as reactive oxygen species (ROS) generated by photosensitizers/sonosensitizers, and could promote infiltration of immune cells. Thereby, it could solve the currently existing sterilization deficiencies of other combined therapeutic modes, for example, bacterial resistance for chemotherapy, low drug permeability for PDT/PCT/SDT, adverse immunoreactions for immunotherapy, etc. Admittedly, PTT-derived synergistic treatments are becoming essential in fighting bacterial infection, especially those caused by antibiotic-resistant strains. This review firstly presents the classical and newly reported photothermal agents (PTAs) in brief. Profoundly, through the introduction of delicately designed nanocomposite platforms, we systematically discuss the versatile photothermal-derived multimodal synergistic therapy with the purpose of sterilization application. At the end, challenges to PTT-derived combinational therapy are presented and promising synergistic bactericidal prospects are anticipated.

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.

Correction to: A multifunctional platform with single-NIR-laser-triggered photothermal and NO release for synergistic therapy against multidrug-resistant Gram-negative bacteria and their biofilms

An amendment to this paper has been published and can be accessed via the original article.