Thermo-responsive triple-function nanotransporter for efficient chemo-photothermal therapy of multidrug-resistant bacterial infection

Nano-enabled sensing approaches for pathogenic bacterial detection

Infectious diseases caused by pathogenic bacteria, especially antibiotic-resistant bacteria, are one of the biggest threats to global health. To date, bacterial contamination is detected using conventional culturing techniques, which are highly dependent on expert users, limited by the processing time and on-site availability. Hence, real-time and continuous monitoring of pathogen levels is required to obtain valuable information that could assist health agencies in guiding prevention and containment of pathogen-related outbreaks. Nanotechnology-based smart sensors are opening new avenues for early and rapid detection of such pathogens at the patient's point-of-care. Nanomaterials can play an essential role in bacterial sensing owing to their unique optical, magnetic, and electrical properties. Carbon nanoparticles, metallic nanoparticles, metal oxide nanoparticles, and various types of nanocomposites are examples of smart nanomaterials that have drawn intense attention in the field of microbial detection. These approaches, together with the advent of modern technologies and coupled with machine learning and wireless communication, represent the future trend in the diagnosis of infectious diseases. This review provides an overview of the recent advancements in the successful harnessing of different nanoparticles for bacterial detection. In the beginning, we have introduced the fundamental concepts and mechanisms behind the design and strategies of the nanoparticles-based diagnostic platform. Representative research efforts are highlighted for in vitro and in vivo detection of bacteria. A comprehensive discussion is then presented to cover the most commonly adopted techniques for bacterial identification, including some seminal studies to detect bacteria at the single-cell level. Finally, we discuss the current challenges and a prospective outlook on the field, together with the recommended solutions.

Biomimetic biodegradable Ag@Au nanoparticle-embedded ureteral stent with a constantly renewable contact-killing antimicrobial surface and antibiofilm and extraction-free properties

Urinary tract infections (UTIs) caused by the contamination of the ureteral stent and the pain associated with secondary stent extractions are worldwide problems in the treatment of urinary tract disorders. Here, we reported a biodegradable, long-term antibacterial, and extraction-free ureteral stent with a constantly renewable contact-killing surface and an antibiofilm function achieved by constructing a hyperbranched poly(amide-amine)-capped Ag shell and Au core nanoparticle (Ag@Au NP)-embedded fiber membrane-structured poly(glycolic acid)/poly(lactic-co-glycolic acid) (PGA/PGLA) ureteral stent. The ureteral stent showed fast contact-killing properties, i.e., 5 min for Escherichia coli and 10 min for Staphylococcus aureus, with an inhibition rate higher than 99%. In addition, gradient degradation of PGA/PGLA endowed the stent with a self-cleaning property and long-term antibacterial function by continuous exfoliation of the stent surface, thereby exposing the inner Ag@Au NPs and eliminating adherent bacteria and proteins. Subsequently, in the 16-day in vitro degradation test, the stent showed durable bactericidal activity, less total release of Ag and Au elements (6.7%, ~8 μg), and low cytotoxicity (with a relative growth rate of >80% of L929 cells). In vivo experiments on a farm pig model showed that the stent exhibited a remarkable antibiofilm property and reduced the level of inflammatory and necrotic cells. After seven days of implantation, the stent showed a gradient degradation behavior and maintained structural integrity without the presence of any large fragments in the urinary system according to the B-ultrasonic examination. The as-developed biodegradable and renewable contact-killing antibacterial strategy was efficient in preparing the ureteral stent with antibiofilm and extraction-free properties to treat stent-induced UTI. Statement of significance This study presents a customized antibiofilm solution for biodegradable implants. Two particularly important aspects of this work are as follows.

Spatiotemporally Controlling the Release of Biological Effectors Enhances Their Effects on Cell Migration and Neurite Outgrowth

It is a major challenge to coordinate topographic cues from scaffolds with the on-demand, sustained release of biological effectors to maximize their performance in tissue regeneration. Here, a system involving masked, photo-triggered release of biological effectors from a temperature-sensitive scaffold for augmented cell migration and neurite outgrowth is reported. The scaffold contains microparticles of a phase-change material (PCM) sandwiched between two layers of electrospun fibers. The biological effectors are co-loaded with a photothermal dye in the PCM microparticles. Under irradiation with a near-infrared laser, the PCM will be melted to swiftly release the biological effectors. By imposing a photomask between the scaffold and the laser, only those microparticles in the irradiated region are melted, enabling a spatial control over the release. By adjusting the photomask, different regions of the scaffold can be sequentially irradiated at designated times, realizing on-demand and sustained release of the biological effectors with spatiotemporal controls. In one demonstration, this method is used to accelerate the directional migration of NIH-3T3 fibroblasts along the uniaxial or radial direction of fiber alignment by controlling the release of epidermal growth factor. In another demonstration, the release of nerve growth factor is managed to significantly promote neurite outgrowth from PC12 cells.

Intelligent Hybrid Hydrogels for Rapid In Situ Detection and Photothermal Therapy of Bacterial Infection

Diseases induced by bacterial infections increasingly threaten the health of people all over the world; thus, it is urgent and significant to early diagnose and effectively eliminate infections to save people's lives. To this end, we synthesized an intelligent hydrogel that integrated in situ visualized diagnosis and photothermal therapy of bacterial infections. By simply and subtly incorporating pH-sensitive bromothymol blue (BTB) and near-infrared (NIR)-absorbing conjugated polymer (termed as PTDBD) into thermosensitive chitosan (CS)-based hydrogel, the synthesized BTB/PTDBD/CS hydrogel can diagnose the acidic microenvironment of Staphylococcus aureus (S. aureus) biofilm and infected wounds by showing visualized color change. After rapid diagnosis, the hydrogel can immediately treat the infection site by local hyperthermia under irradiation of NIR laser (808 nm) and even the stubborn biofilm that is difficult to eradicate. Since the dominating antibacterial mechanism is hyperthermia, the hybrid hydrogel shows broad-spectrum antibacterial activity against Gram-positive, Gram-negative, and drug-resistant bacteria. In addition, it has low cytotoxicity to normal cells and no effect on the main organs of mice. It paves a brand new avenue to develop smart and facile diagnosis and a treatment platform for bacterial infections.

Rational collaborative ablation of bacterial biofilms ignited by physical cavitation and concurrent deep antibiotic release

Bacteria biofilm has extracellular polymeric substances to protect bacteria from external threats, which is a stubborn problem for human health. Herein, a kind of gasifiable nanodroplet is fabricated to ablate Staphylococcus aureus (S. aureus) biofilm. Upon NIR pulsed laser irradiation, the nanodroplets can gasify to generate destructive gas shockwave, which further potentiates initial acoustic cavitation effect, thus synergistically disrupting the protective biofilm and killing resident bacteria. More importantly, the gasification can further promote antibiotic release in deep biofilm for residual bacteria eradication. The nanodroplets not only exhibit deep biofilm penetration capacity and high potency to ablate biofilms, but also good biocompatibility without detectable side effects. In vivo mouse implant model indicates that the nanodroplets can accumulate at the S. aureus infected implant sites. Upon pulsed laser treatment, the nanodroplets efficiently eradicate bacteria biofilm in implanted catheter by synergistic contribution of gas shockwave-enhanced cavitation and deep antibiotic release. Current phase changeable nanodroplets with synergistic physical and chemical therapeutic modalities are promising to combat complex bacterial biofilms with drug resistance, which provides an alternative visual angle for biofilm inhibition in biomedicine.

Rational Design of Conjugated Small Molecules for Superior Photothermal Theranostics in the NIR-II Biowindow

Extensive recent progress has been made on the design and applications of organic photothermal agents for biomedical applications because of their excellent biocompatibility comparing with inorganic materials. One major hurdle for the further development and applications of organic photothermal agents is the rarity of high-performance materials in the second near-infrared (NIR-II) window, which allows deep tissue penetration and causes minimized side effects. Up till now, there have been few reported NIR-II-active photothermal agents and their photothermal conversion efficiencies are relatively low. Herein, optical absorption of π-conjugated small molecules from the first NIR window to the NIR-II window is precisely regulated by molecular surgery of substituting an individual atom. With this technique, the first demonstration of a conjugated oligomer (IR-SS) with an absorption peak beyond 1000 nm is presented, and its nanoparticle achieves a record-high photothermal conversion efficiency of 77% under 1064 nm excitation. The nanoparticles show a good photoacoustic response, photothermal therapeutic efficacy, and biocompatibility in vitro and in vivo. This work develops a strategy to boost the light-harvesting efficiency in the NIR-II window for cancer theranostics, offering an important step forward in advancing the design and application of NIR-II photothermal agents.

Mild temperature photothermal assisted anti-bacterial and anti-inflammatory nanosystem for synergistic treatment of post-cataract surgery endophthalmitis

Rationale: Endophthalmitis, which is one of the severest complications of cataract surgeries, can seriously threaten vision and even lead to irreversible blindness owing to its complicated microenvironment, including both local bacterial infection and severe inflammation. It is urgent to develop a comprehensive treatment for both anti-bacterial and anti-inflammatory effects.

Methods: Herein, we developed AuAgCu₂O-bromfenac sodium nanoparticles (AuAgCu₂O-BS NPs), which was designed to combine anti-bacterial and anti-inflammatory effects for integrated therapy of endophthalmitis after cataract surgery. The AuAgCu₂O-BS NPs could eradicate methicillin-resistant Staphylococcus aureus (MRSA) bacterial strain relied on their photodynamic effects and the release of metal ions (Ag⁺ and Cu⁺) by the hollow AuAgCu₂O nanostructures mediated mild photothermal effects. The anti-inflammatory drug, bromfenac sodium, released from the nanoparticles were able to significantly reduce the local inflammation of the endophthalmitis and promote tissue rehabilitation. In vivo bacterial elimination and anti-inflammation were confirmed by a postcataract endophthalmitis rabbit model.

Results: Excellent antibacterial ability of AuAgCu₂O-BS NPs was verified both in vitro and in vivo. Ophthalmological clinical observation and pathologic histology analysis showed prominent treatment of inflammatory reaction. Importantly, the mild temperature photothermal effect not only promoted the release of metal ions and bromfenac sodium but also avoided the thermal damage of the surrounding tissues, which was more suitable for the practical application of ophthalmology due to the complex structure of the eyeball. Moreover, superior biocompatibility was approved by the preliminary toxicity investigations, including low cytotoxicity, negligible damage to major organs, and stable intraocular pressure.

Conclusions: Our studies of nanosystem provide a promising synergic therapeutic strategy for postcataract endophthalmitis treatment with favorable prognosis and promise in clinical translations.

Biodegradable Nickel Disulfide Nanozymes with GSH-Depleting Function for High-Efficiency Photothermal-Catalytic Antibacterial Therapy

Bacterial infections caused by pathogens have always been a thorny issue that threatens human health, and there is urgent need to develop a new generation of antimicrobial nano-agents and treatments. Herein, biodegradable nickel disulfide (ND) nanozymes as excellent antibacterial agents that integrate excellent photothermal performance, nano-catalysis property, and glutathione (GSH)-depleting function have been successfully constructed. The ND nanozymes can effectively catalyze the decomposition of H₂O₂ to produce ⋅OH, and the hyperthermia of ND nanozymes generated by photothermal therapy (PTT) can further increase its catalytic activity, which provides rapid and effective bacterial killing effect compared with nano-catalytic treatment or PTT alone. Surprisingly, the ND nanozymes have the ability of GSH consumption, thus enhancing its sterilization effect. Moreover, the ND nanozymes are biodegradable nanomaterials that do not cause any significant toxicity in vivo. Collectively, the ND nanozymes with excellent photothermal performance, catalytic activity, and GSH-depleting function are used for high-efficiency sterilization.

•

ND nanozymes have good photothermal and catalysis effect and GSH-depleting function

•

The multifunctional ND nanozymes have achieved satisfactory antibacterial effects

•

The biodegradable ND nanozymes have a wide application in precise sterilization

Nanomaterials for the Photothermal Killing of Bacteria

An upsurge in the multidrug-resistant (MDR) bacterial pestilence is a global cause for concern in terms of human health. Lately, nanomaterials with photothermal effects have assisted in the efficient killing of MDR bacteria, attributable to their uncommon plasmonic, photocatalytic, and structural properties. Examinations of substantial amounts of photothermally enabled nanomaterials have shown bactericidal effects in an optimized time under near-infrared (NIR) light irradiation. In this review, we have compiled recent advances in photothermally enabled nanomaterials for antibacterial activities and their mechanisms. Photothermally enabled nanomaterials are classified into three groups, including metal-, carbon-, and polymer-based nanomaterials. Based on substantial accomplishments with photothermally enabled nanomaterials, we have inferred current trends and their prospective clinical applications.

PB@PDA@Ag nanosystem for synergistically eradicating MRSA and accelerating diabetic wound healing assisted with laser irradiation

The ever-growing threats of multidrug-resistant bacterial infection and chronic wound healing have created an imperative need for the development of novel antibacterial materials and therapeutic strategies, especially for diabetic patients infected with multidrug-resistant bacteria. In this work, the nanocomplexes named as PB@PDA@Ag were used for eradicating multidrug-resistant bacteria and accelerating wound healing of MRSA-infected diabetic model with the assistance of laser irradiation. In vitro results revealed that the combinational strategy exerted a synergistic effect for anti-MRSA through disrupting cell integrity, producing ROS, declining ATP, and oxidizing GSH, comparing with PB@PDA@Ag or NIR laser irradiation alone. Moreover, in vivo assay demonstrated that this system effectively accelerated MRSA-infected diabetic wound healing by mitigating local inflammatory response and up-regulating VEGF expression on the wound bed. Meanwhile, satisfactory biocompatibility and negligible damage to major organs were observed. Altogether, the aforementioned results indicate that the combinational therapy of PB@PDA@Ag and NIR irradiation shows a great potential application in the field of clinic infection.

NIR Light-Driving Barrier-Free Group Rotation in Nanoparticles with an 88.3% Photothermal Conversion Efficiency for Photothermal Therapy

Traditional photothermal therapy requires high-intensity laser excitation for cancer treatments due to the low photothermal conversion efficiency (PCE) of photothermal agents (PTAs). PTAs with ultra-high PCEs can decrease the required excited light intensity, which allows safe and efficient therapy in deep tissues. In this work, a PTA is synthesized with high PCE of 88.3% based on a BODIPY scaffold, by introducing a CF₃ "barrier-free" rotor on the meso-position (tfm-BDP). In both the ground and excited state, the CF₃ moiety in tfm-BDP has no energy barrier to rotation, allowing it to efficiently dissipate absorbed (NIR) photons as heat. Importantly, the barrier-free rotation of CF₃ can be maintained after encapsulating tfm-BDP into polymeric nanoparticles (NPs). Thus, laser irradiation with safe intensity (0.3 W cm^-2 , 808 nm) can lead to complete tumor ablation in tumor-bearing mice after intravenous injection of tfm-BDP NPs. This strategy of "barrier-free rotation" provides a new platform for future design of PTT agents for clinical cancer treatment.

Well-Defined Gold Nanorod/Polymer Hybrid Coating with Inherent Antifouling and Photothermal Bactericidal Properties for Treating an Infected Hernia

Biomedical device-associated infection (BAI) is a great challenge in modern clinical medicine. Therefore, developing efficient antibacterial materials is significantly important and meaningful for the improvement of medical treatment and people's health. In the present work, we developed a strategy of surface functionalization for multifunctional antibacterial applications. A functionalized polyurethane (PU, a widely used biomedical material for hernia repairing) surface (PU-Au-PEG) with inherent antifouling and photothermal bactericidal properties was readily prepared based on a near-infrared (NIR)-responsive organic/inorganic hybrid coating which consists of gold nanorods (Au NRs) and polyethylene glycol (PEG). The PU-Au-PEG showed a high efficiency to resist adhesion of bacteria and exhibited effective photothermal bactericidal properties under 808 nm NIR irradiation, especially against multidrug-resistant bacteria. Furthermore, the PU-Au-PEG could inhibit biofilm formation long term. The biocompatibility of PU-Au-PEG was also proved by cytotoxicity and hemolysis tests. The in vivo photothermal antibacterial properties were first verified by a subcutaneous implantation animal model. Then, the anti-infection performance in a clinical scenario was studied with an infected hernia model. The results of animal experiment studies demonstrated excellent in vivo anti-infection performances of PU-Au-PEG. The present work provides a facile and promising approach to develop multifunctional biomedical devices.

Graphene Oxide Mediated Broad-Spectrum Antibacterial Based on Bimodal Action of Photodynamic and Photothermal Effects

Graphene oxide (GO) with their interesting properties including thermal and electrical conductivity and antibacterial characteristics have many promising applications in medicine. The prevalence of resistant bacteria is considered a public health problem worldwide, herein, GO has been used as a broad spectrum selective antibacterial agent based on the photothermal therapy (PTT)/photodynamic therapy (PDT) effect. The preparation, characterization, determination of photophysical properties of two different sizes of GO is described. In vitro light dose and concentration-dependent studies were performed using Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria based on the PTT/PDT effect used ultra-low doses (65 mW cm-2) of 630 nm light, to achieve efficient bacterial decontamination. The results show that GO and nanographene oxide (nGO) can sensitize the formation of 1O2 and allow a temperature rise of 55°C to 60°C together nGO and GO to exert combined PTT/PDT effect in the disinfection of gram-positive S. aureus and gram-negative E. coli bacteria. A complete elimination of S. aureus and E. coli bacteria based on GO and nGO is obtained by using a dose of 43-47 J cm-2 for high concentration used in this study, and a dose of around 70 J cm-2 for low dose of GO and nGO. The presence of high concentrations of GO allows the bacterial population of S. aureus and E. coli to be more sensitive to the use of PDT/PTT and the efficiency of S. aureus and E. coli bacteria disinfection in the presence of GO is similar to that of nGO. In human neonatal dermal fibroblast, HDFs, no significant alteration to cell viability was promoted by GO, but in nGO is observed a mild damage in the HDFs cells independent of nGO concentration and light exposure. The unique properties of GO and nGO may be useful for the clinical treatment of disinfection of broad-spectrum antimicrobials. The antibacterial results of PTT and PDT using GO in gram-positive and gram-negative bacteria, using low dose light, allow us to conclude that GO and nGO can be used in dermatologic infections, since the effect on human dermal fibroblasts of this treatment is low compared to the antibacterial effect.

Biomimetic anti-inflammatory nano-capsule serves as a cytokine blocker and M2 polarization inducer for bone tissue repair

Controlling of pro-inflammation induced by pro-inflammatory cytokines and anti-inflammatory response induced by M2 macrophages is important for osteogenesis in the process of bone tissue repair. Thus, we fabricated biomimetic anti-inflammatory nano-capsule (BANC) that can block cytokines and promote M2 macrophage polarization, presenting a positive role for bone tissue repair. The BANC is a biomimic nanosystem, coated with lipopolysaccharide-treated macrophage cell membranes with cytokine receptors enveloping gold nanocage (AuNC) as "cytokine blocker", and loaded with resolvin D1 inside into AuNC as "M2 polarization inducer" whose controlled-release could be triggered under near-infrared laser irradiation in sequence, and these chronological events were consistent with the healing process of bone tissue repair. Moreover, in vivo application of femoral bone defects revealed that the BANC composite boron-containing mesoporous bioactive glass scaffolds improved the final effects of bone tissue repair through preventing inflammatory response, promoting M2 polarization in sequence in accord with the in vitro investigation. Hence, cytokine neutralization and M2 macrophage polarization enables the BANC to enhance the bone tissue repair as a biomimetic anti-inflammation effector. Therefore, this study provides potential therapeutic strategies for trauma-mediated or inflammation-related bone defects based on a biomimetic nanomaterial with weakened pro-inflammatory and enhanced anti-inflammatory effects. STATEMENT OF SIGNIFICANCE: Cell membrane-mimic nanomaterials have been popular for blocking natural cell responses for some infection diseases, yet their role in biological process of bone repair is unknown. Here, we fabricated Biomimetic Anti-inflammatory Nano-Capsule (BANC), coated with cell membrane with cytokines receptors on the surface which could neutralize the pro-inflammatory cytokine receptor to block activated pro-inflammation, loaded with Resolvin D1 inside which could be controllably released by NIR irradiation to promote M2 macrophage polarization for the following bone formation during the process of bone repair. Administration of BANC as cytokines blocker and M2 polarization inducer to enhance the bone regeneration, thus presenting a promising potential for the treatment of bone repair and regeneration.

Photothermally Responsive Conjugated Polymeric Singlet Oxygen Carrier for Phase Change-Controlled and Sustainable Phototherapy for Hypoxic Tumor

Hypoxia significantly compromises the therapeutic performance of photodynamic therapy (PDT) owing to the oxygen level which plays a key role in the production of singlet oxygen (¹O₂). Herein, the photothermally responsive phase change materials (PCM) are used to encapsulate 1,4-dimethylnaphthalene-functionalized platinum(II)-acetylide conjugated polymer (CP1) with intense near-infrared (NIR) absorption to prepare new ¹O₂ nanocarriers (CP1-NCs). The 1,4-dimethylnaphthalene moieties in CP1-NCs can trap the ¹O₂ produced from CP1 under irradiation and form a stable endoperoxide. Then, the endoperoxide undergoes cycloreversion to controllably release ¹O₂ via the NIR light-triggered photothermal effect of CP1 and controllable phase change of PCM, which can be used for oxygen-independent PDT for hypoxic tumor. Furthermore, the in vivo luminescence imaging-guided synergistic PDT and photothermal therapy showed better efficiency in tumor ablation. The smart design shows the potent promise of CP1-NCs in PCM-controlled and sustainable phototherapy under tumor hypoxic microenvironment, providing new insights for constructing oxygen-independent precise cancer phototherapeutic platform.

A lipase-responsive antifungal nanoplatform for synergistic photodynamic/photothermal/pharmaco-therapy of azole-resistant Candida albicans infections

A lipase-triggered drug release nanoplatform (PGL-DPP-FLU NPs) for multi-modal antifungal therapy is developed. The lipases secreted by C. albicans can accelerate FLU release. The ROS and heat produced by PGL-DPP-FLU NPs make C. albicans more vulnerable to FLU, thereby PGL-DPP-FLU NPs exhibit high performance for combating azole-resistant C. albicans biofilms and wound infection.

Synthesis and Antibacterial Properties of Novel ZnMn2O4-Chitosan Nanocomposites

The development of productive antibacterial agents from nontoxic materials via a simple methodology has been an immense research contribution in the medicinal chemistry field. Herein, a sol–gel one-pot reaction was used to synthesize hybrid composites of hausmannite–chitosan (Mn₃O₄–CS) and its innovative derivative zinc manganese oxide–chitosan (ZnMn₂O₄–CS). Fixed amounts of CS with different metal matrix w/v ratios of 0.5%, 1.0%, 1.5%, and 2.0% for Mn and Zn precursors were used to synthesize ZnMn₂O₄–CS hybrid composites. X-ray diffraction analysis indicated the formation of polycrystalline tetragonal-structured ZnMn₂O₄ with a CS matrix in the hybrids. Fourier-transform infrared spectroscopic analysis confirmed the formation of ZnMn₂O₄–CS hybrids. Detailed investigations of the surface modifications were conducted using scanning electron microscopy; micrographs at different magnifications revealed that the composites’ surface changed depending on the ratio of the source materials used to synthesize the ZnMn₂O₄–CS hybrids. The antibacterial activity of the Mn₃O₄–CS and ZnMn₂O₄–CS composites was tested against various bacterial species, including Bacillus subtilis, Escherichia coli, Salmonella typhi, and Pseudomonas aeruginosa. The zone of inhibition and minimum inhibitory concentration values were deduced to demonstrate the efficacy of the ZnMn₂O₄–CS nanocomposites as antibacterial agents.