Near-infrared light-controllable on-demand antibiotics release using thermo-sensitive hydrogel-based drug reservoir for combating bacterial infection

Preparation of Vanillic Acid-Loaded Core-Shell Gold Nanospheres/Mesoporous Silica Nanoparticles for the Treatment of Orthopedic Infection

Orthopedic infection is a serious complication in surgeries and remains a great challenge in clinics. Here, the natural antimicrobial compound vanillic acid-loaded gold nanospheres/mesoporous silica nanoparticles (VA@Au-MSNs) were fabricated for chemo-photothermal synergistic therapy to orthopedic infections. The shape and morphology of Au-MSN and VA@Au-MSN were observed by scanning electron microscopy and transmission electron microscopy. The properties of VA@Au-MSN or related components were characterized by dynamic light scattering, thermogravimetric analysis, Brunauer-Emmett-Teller (BET) analysis, and photothermal analysis. Vanillic acid released from VA@Au-MSN was detected in phosphate-buffered saline. A cytotoxicity test and an antibacterial assessment were performed to explore the biosafety and antibacterial activity of VA@Au-MSN, respectively. The results showed that Au-MSN possessed a high BET surface area (458 m²/g). After loading vanillic acid, the BET surface area reduced to 72 m²/g. The loading efficiency of Au-MSN was 18.56%. Under 808 nm laser irradiation, the temperature at the wound site injected with the Au-MSN solution in the mouse increased from 24 to 60 °C within about 12 s. Also, the high temperature could promote the release of vanillic acid from VA@Au-MSN. Additionally, VA@Au-MSN has no obvious cytotoxicity to MC3T3-E1 cells, but the generated local hyperthermia and the VA released from VA@Au-MSN had excellent antibacterial activity against Staphylococcus aureus in a synergistic way. In conclusion, the VA@Au-MSN with biosafety and excellent antibacterial performance might be applied for the treatment of orthopedic infection.

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.

Stimuli-responsive polydopamine-based smart materials

This review provides in-depth insight into the structural engineering of PDA-based materials to enhance their responsive feature and the use of them in construction of PDA-based stimuli-responsive smart materials.

Recent advances in thermo-sensitive hydrogels for drug delivery

Thermo-sensitive hydrogels based on different polymers have been broadly used in the pharmaceutical fields. In this review, the state-of-the-art thermo-sensitive hydrogels for drug delivery are elaborated

New Smart Antimicrobial Hydrogels, Nanomaterials, and Coatings: Earlier Action, More Specific, Better Dosing?

To fight against antibiotic-resistant bacteria adhering and developing on medical devices, which is a growing problem worldwide, researchers are currently developing new "smart" materials and coatings. They consist in delivery of antimicrobial agents in an intelligent way, i.e., only when bacteria are present. This requires the use of new and sophisticated tools combining antimicrobial agents with lipids or polymers, synthetic and/or natural. In this review, three classes of innovative materials are described: hydrogels, nanomaterials, and thin films. Moreover, smart antibacterial materials can be classified into two groups depending on the origin of the stimulus used: those that respond to a nonbiological stimulus (light, temperature, electric and magnetic fields) and those that respond to a biological stimulus related to the presence of bacteria, such as changes in pH or bacterial enzyme secretion. The bacteria presence can induce a pH change that constitutes a first potential biological trigger allowing the system to become active. A second biological trigger signal consists in enzymes produced by bacteria themselves. A complete panel of recent studies will be given focusing on the design of such innovative smart materials that are sensitive to biological triggers.

Rational Design of Self-Assembled Cationic Porphyrin-Based Nanoparticles for Efficient Photodynamic Inactivation of Bacteria

Bacterial infection has become an urgent health problem in the world. Especially, the evolving resistance of bacteria to antibiotics makes the issue more challenging, and thus new treatments to fight these infections are needed. Antibacterial photodynamic therapy (aPDT) is recognized as a novel and promising method to inactivate a wide range of bacteria with few possibilities to develop drug resistance. However, the photosensitizers (PSs) are not effective against Gram-negative bacteria in many cases. Herein, we use conjugated meso-tetra(4-carboxyphenyl)porphine (TCPP) and triaminoguanidinium chloride (TG) to construct self-assembled cationic TCPP-TG nanoparticles (NPs) for efficient bacterial inactivation under visible light illumination. The TCPP-TG NPs can rapidly adhere to both Gram-negative and Gram-positive bacteria and display promoted singlet oxygen (¹O₂) generation compared with TCPP under light irradiation. The high local positive charge density of TCPP-TG NPs facilitates the interaction between the NPs and bacteria. Consequently, the TCPP-TG NPs produce an elevated concentration of local ¹O₂ under light irradiation, resulting in an extraordinarily high antibacterial efficiency (99.9999% inactivation of the representative bacteria within 4 min). Furthermore, the TCPP-TG NPs show excellent water dispersity and stability during 4 months of storage. Therefore, the rationally designed TCPP-TG NPs are a promising antibacterial agent for effective aPDT.

Antibacterial and anti-inflammatory ultrahigh molecular weight polyethylene/tea polyphenol blends for artificial joint applications

Periprosthetic joint infection (PJI) is one of the main causes for the failure of joint arthroplasty. In view of the limited clinical effect of oral/injectable antibiotics and the drug resistance problem, there is a pressing need to develop antibacterial implants with therapeutic antimicrobial properties. In this work, we prepared a highly antibacterial ultrahigh molecular weight polyethylene (UHMWPE) implant by incorporating tea polyphenols. The presence of tea polyphenols not only improved the oxidation stability of irradiated UHMWPE, but also gave it the desirable antibacterial property. The potent antibacterial activity was attributed to the tea polyphenols that produced excess intracellular reactive oxygen species and destroyed the bacterial membrane structure. The tea polyphenol-blended UHMWPE had no biological toxicity to human adipose-derived stem cells and effectively reduced bacteria-induced inflammation in vivo. These results indicate that tea polyphenol-blended UHMWPE is promising for joint replacement prostheses with multifunctionality to meet patient satisfaction.

Fabrication of chitosan-polyvinyl alcohol and silk electrospun fiber seeded with differentiated keratinocyte for skin tissue regeneration in animal wound model

Hybrid fibrous mat containing cell interactive molecules offers the ability to deliver the cells and drugs in wound bed, which will help to achieve a high therapeutic treatment. In this study, a co-electrospun hybrid of polyvinyl alcohol (PVA), chitosan (Ch) and silk fibrous mat was developed and their wound healing potential by localizing bone marrow mesenchymal stem cells (MSCs)-derived keratinocytes on it was evaluated in vitro and in vivo. It was expected that fabricated hybrid construct could promote wound healing due to its structure, physical, biological specifications. The fabricated fibrous mats were characterized for their structural, mechanical and biochemical properties. The shape uniformity and pore size of fibers showed smooth and homogenous structures of them. Fourier transform infrared spectroscopy (FTIR) verified all typical absorption characteristics of Ch-PVA + Silk polymers as well as Ch-PVA or pure PVA substrates. The contact angle and wettability measurement of fibers showed that mats found moderate hydrophilicity by addition of Ch and silk substrates compared with PVA alone. The mechanical features of Ch-PVA + Silk fibrous mat increase significantly through co-electrospun process as well as hybridization of these synthetic and natural polymers. Higher degrees of cellular attachment and proliferation obtained on Ch-PVA + Silk fibers compared with PVA and Ch-PVA fibers. In terms of the capability of Ch-PVA + Silk fibers and MSC-derived keratinocytes, histological analysis and skin regeneration results showed this novel fibrous construct could be suggested as a skin substitute in the repair of injured skin and regenerative medicine applications.

Near-Infrared-Controlled Nanoplatform Exploiting Photothermal Promotion of Peroxidase-like and OXD-like Activities for Potent Antibacterial and Anti-biofilm Therapies

Nanozymes that mimic peroxidase (POD) activity can convert H₂O₂ into bactericidal free radicals, which is referred to as chemodynamic therapy (CDT). High glutathione (GSH) levels in the infectious tissue severely limit the performance of CDT. Herein, we report a near-infrared-controlled antibacterial nanoplatform that is based on encapsulating tungsten sulfide quantum dots (WS₂QDs) and the antibiotic vancomycin in a thermal-sensitive liposome. The system exploits the photothermal sensitivity of the WS₂QDs to achieve selective liposome rupture for the targeted drug delivery. We determined that WS₂QDs show a strong POD-like activity under physiological conditions and the oxidase-like activity, which can oxidate GSH to further improve the CDT efficacy. Moreover, we found that increased temperature promotes multiple enzyme-mimicking activities of WS₂QDs. This platform exerts antibacterial effects against Gram-positive Mu50 (a vancomycin-intermediate Staphylococcus aureus reference strain) and Gram-negative Escherichia coli and disrupts biofilms for improved penetration of therapeutic agents inside biofilms. In vivo studies with mice bearing Mu50-caused skin abscess revealed that this platform confers potent antibacterial activity without obvious toxicity. Accordingly, our work illustrates that the photothermal and nanozyme properties of WS₂QDs can be deployed alongside a conventional therapeutic to achieve synergistic chemodynamic/photothermal/pharmaco therapy for powerful antibacterial effects.

Development of nanosilver doped carboxymethyl chitosan-polyamideamine alginate composite dressing for wound treatment

Nowadays, treatment to the infected wounds caused by bacterial even multi-resistant bacterial strains and subsequently complete skin regeneration remain a critical clinical challenge. Herein, a novel multi-functional platform (Alg/1.0Ag@CMC-PAMAM/PRP) was prepared as wound dressings by mixing platelet rich plasma (PRP) with the sodium alginate (Alg) based dressing containing nano silver (Ag)-doped carboxymethyl chitosan grafted polyamideamine (Ag@CMC-PAMAM) cationic polymers. The present dressings exhibited high swelling, suitable water vapor transmission rate (WVTR), and good mechanical properties and degradability, as well as sustained release of PRP. Besides, the component of Ag@CMC-PAMAM nanoparticles endow them with excellent antibacterial performance, while the incorporation of PRP promotes the effect of anti-inflammatory and angiogenesis by up-regulating relative activity factor expression of TGF-β1, CD31 and α-SMA and down-regulating the inflammatory-relative genes including TNF-α, IL-6 and IL-1β, all of which promote the closure of wound and produce a superior healing effect to the commercial Aquacel Ag group. This work indicates that the prepared Alg/1.0Ag@CMC-PAMAM/PRP wound dressing is a promising biomaterial with synergistic effect of antibacterial property and wound healing.

Phototherapy-based combination strategies for bacterial infection treatment

The development of nanomedicine is expected to provide an innovative direction for addressing challenges associated with multidrug-resistant (MDR) bacteria. In the past decades, although nanotechnology-based phototherapy has been developed for antimicrobial treatment since it rarely causes bacterial resistance, the clinical application of single-mode phototherapy has been limited due to poor tissue penetration of light sources. Therefore, combinatorial strategies are being developed. In this review, we first summarized the current phototherapy agents, which were classified into two functional categories: organic phototherapy agents (e.g., small molecule photosensitizers, small molecule photosensitizer-loaded nanoparticles and polymer-based photosensitizers) and inorganic phototherapy agents (e.g., carbo-based nanomaterials, metal-based nanomaterials, composite nanomaterials and quantum dots). Then the development of emerging phototherapy-based combinatorial strategies, including combination with chemotherapy, combination with chemodynamic therapy, combination with gas therapy, and multiple combination therapy, are presented and future directions are further discussed. The purpose of this review is to highlight the potential of phototherapy to deal with bacterial infections and to propose that the combination therapy strategy is an effective way to solve the challenges of single-mode phototherapy.

Low-intensity near-infrared light-triggered spatiotemporal antibiotics release and hyperthermia by natural polysaccharide-based hybrid hydrogel for synergistic wound disinfection

Photothermal sterilization is a promising and effective treatment method in treating bacterial infection. Generally, a widely employed light source in photothermal sterilization inevitably damages the skin tissue due to the high-intensity irradiation dose. How to provide useful antibacterial outcomes without light-triggered skin damage is a challenge for photothermal sterilization. In this work, a novel antibacterial hydrogel (VAT hydrogel, the abbreviation for vancomycin-agarose-ferric tannate hydrogel) has been successfully constructed by the natural polysaccharide hydrogel (AG) encapsulating ferric tannate (TA-Fe) nanoparticles and vancomycin. The VAT hydrogel exhibited the outstanding photothermal properties and controllable antibiotics release. With the results of antibacterial assays, the VAT hydrogel revealed the superior effectiveness of synergistic wound disinfection by the low-intensity near-infrared light-triggered spatiotemporal antibiotics release and hyperthermia. More importantly, the VAT hydrogels possessed the good biocompatibility. With the outstanding synergistic sterilizing effect and excellent biocompatibility, the VAT hydrogel would be a promising candidate for bacteria-associated wound infections.

Antibacterial Hybrid Hydrogels

Bacterial infectious diseases and bacterial-infected environments have been threatening the health of human beings all over the world. In view of the increased bacteria resistance caused by overuse or improper use of antibiotics, antibacterial biomaterials are developed as the substitutes for antibiotics in some cases. Among them, antibacterial hydrogels are attracting more and more attention due to easy preparation process and diversity of structures by changing their chemical cross-linkers via covalent bonds or noncovalent physical interactions, which can endow them with various specific functions such as high toughness and stretchability, injectability, self-healing, tissue adhesiveness and rapid hemostasis, easy loading and controlled drug release, superior biocompatibility and antioxidation as well as good conductivity. In this review, the recent progress of antibacterial hydrogel including the fabrication methodologies, interior structures, performances, antibacterial mechanisms, and applications of various antibacterial hydrogels is summarized. According to the bacteria-killing modes of hydrogels, several representative hydrogels such as silver nanoparticles-based hydrogel, photoresponsive hydrogel including photothermal and photocatalytic, self-bacteria-killing hydrogel such as inherent antibacterial peptides and cationic polymers, and antibiotics-loading hydrogel are focused on. Furthermore, current challenges of antibacterial hydrogels are discussed and future perspectives in this field are also proposed.

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.

Eradicating Infecting Bacteria while Maintaining Tissue Integration on Photothermal Nanoparticle-Coated Titanium Surfaces

Photothermal nanoparticles locally release heat when irradiated by near-infrared (NIR). Clinical applications initially involved tumor treatment, but currently extend toward bacterial infection control. Applications toward much smaller, micrometer-sized bacterial infections, however, bear the risk of collateral damage by dissipating heat into tissues surrounding an infection site. This can become a complication when photothermal nanoparticle coatings are clinically applied on biomaterial surfaces requiring tissue integration, such as titanium-made, bone-anchored dental implants. Dental implants can fail due to infection in the pocket formed between the implant screw and the surrounding soft tissue ("peri-implantitis"). We address the hitherto neglected potential complication of collateral tissue damage by evaluating photothermal, polydopamine nanoparticle (PDA-NP) coatings on titanium surfaces in different coculture models. NIR irradiation of PDA-NP-coated (200 μg/cm2) titanium surfaces with adhering Staphylococcus aureus killed staphylococci within an irradiation time window of around 3 min. Alternatively, when covered with human gingival fibroblasts, this irradiation time window maintained surface coverage by fibroblasts. Contaminating staphylococci on PDA-NP-coated titanium surfaces, as can be per-operatively introduced, reduced surface coverage by fibroblasts, and this could be prevented by NIR irradiation for 5 min or longer prior to allowing fibroblasts to adhere and grow. Negative impacts of early postoperative staphylococcal challenges to an existing fibroblast layer covering a coated surface were maximally prevented by 3 min NIR irradiation. Longer irradiation times caused collateral fibroblast damage. Late postoperative staphylococcal challenges to a protective keratinocyte layer covering a fibroblast layer required 10 min NIR irradiation for adverting a staphylococcal challenge. This is longer than foreseen from monoculture studies because of additional heat uptake by the keratinocyte layer. Summarizing, photothermal treatment of biomaterial-associated infection requires precise timing of NIR irradiation to prevent collateral damage to tissues surrounding the infection site.

Melanin and Melanin-Like Hybrid Materials in Regenerative Medicine

Melanins are a group of dark insoluble pigments found widespread in nature. In mammals, the brown-black eumelanins and the reddish-yellow pheomelanins are the main determinants of skin, hair, and eye pigmentation and play a significant role in photoprotection as well as in many biological functions ensuring homeostasis. Due to their broad-spectrum light absorption, radical scavenging, electric conductivity, and paramagnetic behavior, eumelanins are widely studied in the biomedical field. The continuing advancements in the development of biomimetic design strategies offer novel opportunities toward specifically engineered multifunctional biomaterials for regenerative medicine. Melanin and melanin-like coatings have been shown to increase cell attachment and proliferation on different substrates and to promote and ameliorate skin, bone, and nerve defect healing in several in vivo models. Herein, the state of the art and future perspectives of melanins as promising bioinspired platforms for natural regeneration processes are highlighted and discussed.

The antibacterial and antibiofilm activities of mesoporous hollow Fe3O4 nanoparticles in an alternating magnetic field

Unrestricted usage of antibiotics has accelerated the emergence of new strains of microorganisms with antimicrobial resistance (AMR) and the development of therapeutic technologies that do not rely only on antibiotics. Herein, mesoporous hollow Fe₃O₄ nanoparticles (MHFPs) were synthesized by a one-pot hydrothermal method, and the feasibility and possible mechanism of using alternating magnetic field (AMF) with MHFPs to kill Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were explored. The presence of the AMF (2.5 kW, 210 kHz) combined with the MHFPs resulted in a dramatic decrease in colony forming units (CFU) for E. coli and S. aureus in 25 min compared with the pure MHFPs at concentrations of 500, 800 and 1000 μg mL^-1. Macroscopic hyperthermia was proved not to be the sole reason for the phenomenon. Visible membrane damage was demonstrated by live/dead staining, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) assays. Besides, the permeability and integrity changes of the cell membrane were then quantitatively confirmed by measuring the relative electrical conductivity. In addition, bacterial biofilms were significantly dispersed in the presence of MHFPs and AMF. These results suggested that under the mediation of AMF, MHFPs can potentially serve as an efficient nonantibiotic therapeutic platform to disperse bacterial biofilms and inactivate bacteria by damaging the cell membrane of the bacteria.

Nanoparticle-Based Wound Dressing: Recent Progress in the Detection and Therapy of Bacterial Infections

Bacterial infections in wounds often delay the healing process, and may seriously threaten human life. It is urgent to develop wound dressings to effectively detect and treat bacterial infections. Nanoparticles have been extensively used in wound dressings because of their specific properties. This review highlights the recent progress on nanoparticle-based wound dressings for bacterial detection and therapy. Specifically, nanoparticles have been applied as intrinsic antibacterial agents or drug delivery vehicles to treat bacteria in wounds. Moreover, nanoparticles with photothermal or photodynamic property have also been explored to endow wound dressings with significant optical properties to further enhance their bactericidal effect. More interestingly, nanoparticle-based smart dressings have been recently explored for bacteria detection and treatment, which enables an accurate assessment of bacterial infection and a more precise control of on-demand therapy.

Combating the Coronavirus Pandemic: Early Detection, Medical Treatment, and a Concerted Effort by the Global Community

The World Health Organization (WHO) has declared the outbreak of 2019 novel coronavirus, known as 2019-nCoV, a pandemic, as the coronavirus has now infected over 2.6 million people globally and caused more than 185,000 fatalities as of April 23, 2020. Coronavirus disease 2019 (COVID-19) causes a respiratory illness with symptoms such as dry cough, fever, sudden loss of smell, and, in more severe cases, difficulty breathing. To date, there is no specific vaccine or treatment proven effective against this viral disease. Early and accurate diagnosis of COVID-19 is thus critical to curbing its spread and improving health outcomes. Reverse transcription-polymerase chain reaction (RT-PCR) is commonly used to detect the presence of COVID-19. Other techniques, such as recombinase polymerase amplification (RPA), loop-mediated isothermal amplification (LAMP), clustered regularly interspaced short palindromic repeats (CRISPR), and microfluidics, have allowed better disease diagnosis. Here, as part of the effort to expand screening capacity, we review advances and challenges in the rapid detection of COVID-19 by targeting nucleic acids, antigens, or antibodies. We also summarize potential treatments and vaccines against COVID-19 and discuss ongoing clinical trials of interventions to reduce viral progression.

Poly(selenoviologen)-Assembled Upconversion Nanoparticles for Low-Power Single-NIR Light-Triggered Synergistic Photodynamic and Photothermal Antibacterial Therapy

The development of a highly effective photosensitizer (PS) that can be activated with a low-power single light is a pressing issue. Herein, we report a PS for synergistic photodynamic and photothermal therapy constructed through self-assembly of poly(selenoviologen) on the surface of core-shell NaYF₄:Yb/Tm@NaYF₄ upconversion nanoparticles. The hybrid UCNPs/PSeV PS showed strong ROS generation ability and high photothermal conversion efficiency (∼52.5%) under the mildest reported-to-date irradiation conditions (λ = 980 nm, 150 mW/cm², 4 min), leading to a high efficiency in killing methicillin-resistant Staphylococcus aureus (MRSA) both in vitro and in vivo. Remarkably, after intravenous injection, the reported PS accumulated preferentially in deep MRSA-infected tissues and achieved an excellent therapeutic index. This PS design realizes a low-power single-NIR light-triggered synergistic phototherapy and provides a simple and versatile strategy to develop safe clinically translatable agents for efficient treatment of deep tissue bacterial inflammations.

Nanoparticle-Loaded Hydrogel for the Light-Activated Release and Photothermal Enhancement of Antimicrobial Peptides

Rising concerns over multidrug-resistant bacteria have necessitated an expansion to the current antimicrobial arsenal and forced the development of novel delivery strategies that enhance the efficacy of existing treatments. Antimicrobial peptides (AMPs) are a promising antibiotic alternative that physically disrupts the membrane of bacteria, resulting in rapid bactericidal activity; however, clinical translation of AMPs has been hindered by their susceptibility to protease degradation. Through the co-loading of liposomes encapsulating model AMP, IRIKIRIK-CONH₂ (IK8), and gold nanorods (AuNRs) into a poly(ethylene glycol) (PEG) hydrogel, we have demonstrated the ability to protect encapsulated materials from proteolysis and provide the first instance of the triggered AMP release. Laser irradiation at 860 nm, at 2.1 W cm^-2, for 10 min led to the photothermal triggered release of IK8, resulting in bactericidal activity against Gram-negative Pseudonomas aeruginosa and Gram-positive Staphylococcus aureus. Furthermore, by increasing the laser intensity to 2.4 W cm^-2, we have shown the thermal enhancement of AMP activity. The photothermal triggered release, and enhancement of AMP efficacy, was demonstrated to treat two rounds of fresh S. aureus, indicating that the therapeutic gel has the potential for multiple rounds of treatment. Taken together, this novel therapeutic hydrogel system demonstrates the stimuli-responsive release of AMPs with photothermal enhanced antimicrobial efficacy to treat pathogenic bacteria.

PLGA microsphere-based composite hydrogel for dual delivery of ciprofloxacin and ginsenoside Rh2 to treat Staphylococcus aureus-induced skin infections

When antibiotic-resistant pathogenic bacteria pose a high threat to human health, bacterial multidrug efflux pumps become major contributors to the high-level antibiotic resistance in most microorganisms. Since traditional antibiotics are still indispensable currently, we report a dual drug delivery system to maximize the antibacterial efficacy of antibiotics by inhibiting efflux pumps in bacteria before their exposure to antibiotics. In this research, a microsphere/hydrogel composite was constructed from ciprofloxacin (Cip)-loaded poly (lactic-co-glycolic acid) (PLGA) microspheres and ginsenoside Rh2 (G-Rh2) dispersed thermo-sensitive hydrogel to treat skin infections. In vitro drug release studies indicated that while G-Rh2 in hydrogel presented a faster and short-term release manner to rapidly inhibit the NorA efflux pumps, Cip showed a sustained and long-term release behavior to provide a local high concentration gradient for facilitating drug percutaneous penetration. The combination of Cip and G-Rh2 demonstrated a high degree of synergism against both methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA), hence significantly improving their in vitro antibacterial activity and efficiency. Moreover, the antibacterial performance of the microsphere/hydrogel composite with a sequential release profile is superior to that of other formulations in mouse model of MRSA skin infections, indicating its great potential to treat antibiotic-resistant skin infections.

In vivo photothermal inhibition of methicillin-resistant Staphylococcus aureus infection by in situ templated formulation of pathogen-targeting phototheranostics

Bacterial infection has caused a serious threat to human public health. Methicillin-resistant Staphylococcus aureus (MRSA) is a representative drug-resistant bacterium, which is difficult to eradicate completely, resulting in high infection probability with severe mortality. Herein, pathogen-targeting phototheranostic nanoparticles, Van-OA@PPy, are developed for efficient elimination of MRSA infection. Van-OA@PPy nanoparticles are fabricated from the in situ templated formation of polypyrrole (PPy) in the presence of ferric ions (Fe³⁺) and a polymer template, hydrophilic poly(2-hydroxyethyl methacrylate-co-N,N-dimethyl acrylamide), P(HEMA-co-DMA). PPy nanoparticles are further coated with vancomycin conjugated oleic acid (Van-OA) to afford the resultant pathogen-targeting Van-OA@PPy. A high photothermal conversion efficiency of ∼49.4% is achieved. MRSA can be efficiently killed due to sufficient nanoparticle adhesion and fusion with MRSA, followed by photothermal therapy upon irradiation with an 808 nm laser. Remarkable membrane damage of MRSA is observed, which contributes greatly to the inhibition of MRSA infection. Furthermore, the nanoparticles have high stability and good biocompatibility without causing any detectable side effects. On the other hand, residual Fe³⁺ and PPy moieties in Van-OA@PPy endow the nanoparticles with magnetic resonance (MR) imaging and photoacoustic (PA) imaging potency, respectively. The current strategy has the potential to inspire further advances in precise diagnosis and efficient elimination of MRSA infection in biomedicine.

Near-Infrared Light-Triggered Nitric-Oxide-Enhanced Photodynamic Therapy and Low-Temperature Photothermal Therapy for Biofilm Elimination

Photothermal treatment (PTT) involving a combination of therapeutic modalities recently emerged as an efficient alternative for combating biofilm. However, PTT-related local high temperature may destroy the surrounding healthy tissues. Herein, we present an all-in-one phototherapeutic nanoplatform consisting of l-arginine (l-Arg), indocyanine green (ICG), and mesoporous polydopamine (MPDA), namely, AI-MPDA, to eliminate the already-formed biofilm. The fabrication process included surface modification of MPDA with l-Arg and further adsorption of ICG via π-π stacking. Under near-infrared (NIR) exposure, AI-MPDA not only generated heat but also produced reactive oxygen species, causing a cascade catalysis of l-Arg to release nitric oxide (NO). Under NIR irradiation, biofilm elimination was attributed to the NO-enhanced photodynamic therapy and low-temperature PTT (≤45 °C). Notably, the NIR-triggered all-in-one strategy resulted in severe destruction of bacterial membranes. The phototherapeutic AI-MPDA also displayed good cytocompatibility. NIR-irradiated AI-MPDA nanoparticles not only prevented bacterial colonization but also realized a rapid recovery of infected wounds. More importantly, the all-in-one phototherapeutic platform displayed effective biofilm elimination with an efficiency of around 100% in a abscess formation model. Overall, this low-temperature phototherapeutic platform provides a reliable tool for combating already-formed biofilms in clinical applications.

Nanomaterials for Nanotheranostics: Tuning Their Properties According to Disease Needs

Nanotheranostics is one of the biggest scientific breakthroughs in nanomedicine. Most of the currently available diagnosis and therapies are invasive, time-consuming, and associated with severe toxic side effects. Nanotheranostics, on the other hand, has the potential to bridge this gap by harnessing the capabilities of nanotechnology and nanomaterials for combined therapeutics and diagnostics with markedly enhanced efficacy. However, nanomaterial applications in nanotheranostics are still in its infancy. This is due to the fact that each disease has a particular microenvironment with well-defined characteristics, which promotes deeper selection criteria of nanomaterials to meet the disease needs. In this review, we have outlined how nanomaterials are designed and tailored for nanotheranostics of cancer and other diseases such as neurodegenerative, autoimmune (particularly on rheumatoid arthritis), and cardiovascular diseases. The penetrability and retention of a nanomaterial in the biological system, the therapeutic strategy used, and the imaging mode selected are some of the aspects discussed for each disease. The specific properties of the nanomaterials in terms of feasibility, physicochemical challenges, progress in clinical trials, its toxicity, and their future application on translational medicine are addressed. Our review meticulously and critically examines the applications of nanotheranostics with various nanomaterials, including graphene, across several diseases, offering a broader perspective of this emerging field.

Dual responsive linalool capsules with high loading ratio for excellent antioxidant and antibacterial efficiency

Linalool is a main component in different naturally derived essential oils, and widely used in household, personal care, food and therapeutic formulations. However, the application is limited due to its high volatility and low stability. In this study, an effective encapsulation with high loading ratio was built up together with thermal-redox dual responsiveness and controlled release properties. The emulsified linalool droplets were modified with carbon-carbon double bonds, followed by the precipitation polymerization with thermal sensitive monomer, N-vinyl caprolactam. The average size and the loading ratio of the prepared linalool capsules were 1.4 μm and 50.41 wt%. The linalool capsules exhibited thermal-redox dual responsive properties and the antioxidant-antibacterial performance. Especially, responding to the stimuli mimicking practical circumstance, the synthesized capsules presented excellent bacteria inhibiting effect. This work may open a new path for fragrance and essential oil encapsulation, enlarging them as the green biological antibacterial agents in different 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.

Incorporation of dumbbell-shaped and Y-shaped cross-linkers in adjustable pullulan/polydopamine hydrogels for selective adsorption of cationic dyes

Hydrogel adsorbents have attracted considerable attention due to their sludge minimization, good water permeability and renewable performance. Here, a promising strategy for the one-step preparation of pullulan/polydopamine hybird hydrogels (PPGels) was presented. Dumbbell-shaped cross-linker neopentyl glycol diglycidyl ether (NGDE, 2 arms) and Y-shaped cross-linker trimethylolpropane triglycidyl ether (TTE, 3 arms) were selected to study the relationship between cross-linker structure and hydrogel performances. The NGDE possessing less molecular repulsive force and higher reactivity demonstrated more effective cross-linking with the pullulan, which leaded to a decrease in pore size of the hydrogel. Meanwhile, the introduction of polydopamine significantly enhanced the adsorption ability and gave the resulting hybrid gel the specific selectivity toward cationic dyes (96 mg/g for crystal violet, 25.8 mg/g for methylene blue and barely not adsorption for azophloxine). Our data suggested that the electrostatic interaction played a vital role in the dye adsorption process, and the adsorption data could be explained by pseudo-second-order model and Langmuir isotherm model. Furthermore, the obtained PPGel could be easily separated after adsorption. This study describes the relationship between cross-linker structure and properties of pullulan/polydopamine hybrid gels, which provides a new strategy to create polysaccharide-based adsorbents for wastewater remediation.

Thermosensitive and pH-responsive tannin-containing hydroxypropyl chitin hydrogel with long-lasting antibacterial activity for wound healing

Polysaccharide hydrogels have been widely used as wound dressings because of their biocompatibility and ability to provide moist environment for wound healing. However, bacterial infection often delays the healing process. Herein, a novel thermosensitive and pH-sensitive hydroxypropyl chitin/tannic acid/ferric ion (HPCH/TA/Fe) composite hydrogel was fabricated by a simple assembly. The pre-cooled hydrogel precursor solution can be injected onto the irregular wound area and gel rapidly at physiological temperature. The TA not only acted as a crosslinker to enhance mechanical properties of the hydrogel, but also as an antibacterial agent which could be sustainably released in response to the acidic environment. The composite hydrogel showed excellent broad-spectrum antibacterial activity up to 7 days with negligible cytotoxicity. Moreover, the hydrogel can inhibit bacterial infection and accelerate the wound healing process without scars in the mouse experiment. These results indicate the potential application of this composite hydrogel for the infected wound healing.

Redox-Channeling Polydopamine-Ferrocene (PDA-Fc) Coating To Confer Context-Dependent and Photothermal Antimicrobial Activities

Microbial disinfection associated with medical device surfaces has been an increasing need, and surface modification strategies such as antibacterial coatings have gained great interest. Here, we report the development of polydopamine-ferrocene (PDA-Fc)-functionalized TiO₂ nanorods (Ti-Nd-PDA-Fc) as a context-dependent antibacterial system on implant to combat bacterial infection and hinder biofilm formation. In this work, two synergistic antimicrobial mechanisms of the PDA-Fc coating are proposed. First, the PDA-Fc coating is redox-active and can be locally activated to release antibacterial reactive oxygen species (ROS), especially ·OH in response to the acidic microenvironment induced by bacteria colonization and host immune responses. The results demonstrate that redox-based antimicrobial activity of Ti-Nd-PDA-Fc offers antibacterial efficacy of over 95 and 92% against methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli), respectively. Second, the photothermal effect of PDA can enhance the antibacterial capability upon near-infrared (NIR) irradiation, with over 99% killing efficacy against MRSA and E. coli, and even suppress the formation of biofilm through both localized hyperthermia and enhanced ·OH generation. Additionally, Ti-Nd-PDA-Fc is biocompatible when tested with model pre-osteoblast MC-3T3 E1 cells and promotes cell adhesion and spreading presumably due to its nanotopographical features. The MRSA-infected wound model also indicates that Ti-Nd-PDA-Fc with NIR irradiation can effectively eliminate bacterial infection and suppress host inflammatory responses. We believe that this study demonstrates a simple means to create biocompatible redox-active coatings that confer context-dependent antibacterial activities to implant surfaces.

Dual-Enzyme Crosslinking and Post-polymerization for Printing of Polysaccharide-Polymer Hydrogel

Polymer hydrogels are ideal bioprinting scaffolds for cell-loading and tissue engineering due to their extracellular-matrix-like structure. However, polymer hydrogels that are easily printed tend to have poor strength and fragile properties. The gradually polymerized reinforcement after hydrogel printing is a good method to solve the contradiction between conveniently printed and high mechanical strength requirement. Here, a new succinct approach has been developed to fabricate the printable composite hydrogels with tunable strength. We employed the HRP@GOx dual enzyme system to initiate the immediate crosslinking of chondroitin sulfate grafted with tyrosine and the gradual polymerization of monomers to form the composite hydrogels. The detailed two-step gelation mechanism was confirmed by the Fluorescence spectroscopy, Electron paramagnetic resonance spectroscopy and Gel permeation chromatography, respectively. The final composite hydrogel combines the merits of enzymatic crosslinking hydrogels and polymerized hydrogels to achieve adjustable mechanical strength and facile printing performance. The dual-enzyme regulated polymer composite hydrogels are the promising bioscaffolds as organoid, implanted materials, and other biomedical applications.

Light-Activable On-Demand Release of Nano-Antibiotic Platforms for Precise Synergy of Thermochemotherapy on Periodontitis

The overprescription and improper use of antibiotics have contributed to the evolution of bacterial resistance, making it urgent to develop alternative therapies and agents with better efficacy as well as less toxicity to combat bacterial infections and keep new resistance from developing. In this work, a novel light-activable nano-antibiotic platform (TC-PCM@GNC-PND) was constructed by the incorporation of gold nanocages (GNC) and two thermosensitive gatekeepers, phase-change materials (PCM) and thermosensitive polymer poly(N-isopropylacrylamide-co-diethylaminoethyl methacrylate) (PND), to realize precisely the synergy of photothermal and antimicrobial drugs. GNC exhibits an excellent photothermal effect owing to its strong absorbance in the near-infrared (NIR) region, and hollow interiors make it a favorable vehicle for loading various antibiotics such as tetracycline (TC). The release of the encapsulated drugs could be precisely controlled by NIR light through the dual thermosensitive interaction of liquid-solid transition of PCM and coil-granule transition of PND, improving efficacy and alleviating side effects with on-demand drug release. The thermosensitive hydrogel was formed in situ upon application with body temperature, enhancing retention of the antimicrobial agent in local infectious sites. Highly effective ablation of bacteria is achieved both in vitro and in periodontitis models with little toxicity owing to the synergy of photothermal effects and chemotherapeutic drug release induced by NIR. This study could provide guidance for the design of antibacterial materials and shed substantial light on synergistic treatment.

Palladium nanosheet-knotted injectable hydrogels formed via palladium-sulfur bonding for synergistic chemo-photothermal therapy

Nanoparticle (NP)-based hydrogels that can introduce synergistic advantages to the novel three-dimensional scaffold have garnered much attention recently. However, the application of NP-crosslinked hydrogels still remains challenging due to the complicated synthesis and/or modification of the NPs and the changed properties of the NPs after gelation. Herein, a novel palladium nanosheet (Pd NS)-based hydrogel (Pd Gel) with Pd NSs as crosslinkers was obtained by simply mixing Pd NSs with thiol-terminated four-arm polyethylene glycol (4arm-PEG-thiol). It was found that the formed Pd Gel was injectable, possibly due to the dynamic Pd-S bonds formed between Pd NSs and 4arm-PEG-thiol. In addition, compared with free Pd NSs, the Pd NSs within the hydrogel exhibited a significantly higher stability. We have further demonstrated that the formed hydrogel could encapsulate the commonly used anticancer drug doxorubicin (DOX) to form DOX@Pd Gel for combined chemo-photothermal therapy. Particularly, Pd NSs with a high absorption in the near-infrared (NIR) region could convert the energy of NIR laser into heat with a high efficiency, which is beneficial for photothermal therapy. Moreover, DOX@Pd Gel could maintain a sustainable release of DOX and the NIR laser irradiation could accelerate this drug release process. Then, the explosively released DOX and the hyperthermia generated from Pd NSs under NIR laser irradiation acted in a synergistic way to realize the combined therapeutic effect of the chemo-photothermal treatment. Finally, the in vivo anticancer effect and safety of the combined therapy were also verified by the tumor-bearing mouse model. Taken together, this work constructs a NP-crosslinked, NIR laser-activatable and injectable photothermal hydrogel via dynamic Pd-S bonding, and demonstrates that the hydrogel allows us to release DOX more precisely, eliminate tumor more effectively and inhibit tumor metastasis more persistently, which will advance the development of novel anticancer strategies.

A near-infrared light-responsive multifunctional nanocomposite hydrogel for efficient and synergistic antibacterial wound therapy and healing promotion

A multifunctional nanocomposite hydrogel for synergistic antibacterial wound therapy and healing promotion.

Transforming sustained release into on-demand release: self-healing guanosine–borate supramolecular hydrogels with multiple responsiveness for Acyclovir delivery

Supramolecular hydrogels derived from natural nucleoside have promising applications for on-demand drug release with controlled on/off switch and adjustable release kinetics in response to various stimuli.

Glycol Chitosan: A Water-Soluble Polymer for Cell Imaging and Drug Delivery

Glycol chitosan (GC), a water-soluble chitosan derivative with hydrophilic ethylene glycol branches, has both hydrophobic segments for the encapsulation of various drugs and reactive functional groups for facile chemical modifications. Over the past two decades, a variety of molecules have been physically encapsulated within or chemically conjugated with GC and its derivatives to construct a wide range of functional biomaterials. This review summarizes the recent advances of GC-based materials in cell surface labeling, multimodal tumor imaging, and encapsulation and delivery of drugs (including chemotherapeutics, photosensitizers, nucleic acids, and antimicrobial agents) for combating cancers and microbial infections. Besides, different strategies for GC modifications are also highlighted with the aim to shed light on how to endow GC and its derivatives with desirable properties for therapeutic purposes. In addition, we discuss both the promises and challenges of the GC-derived biomaterials.

Facile and eco-friendly fabrication of polysaccharides-based nanocomposite hydrogel for photothermal treatment of wound infection

Nowadays, photothermal killing of pathogenic bacteria and treatment of wound infection have attracted great attention owing to effectively avoiding the drawbacks of traditional antibiotics. In this work, an agarose (AG)-based hydrogel containing tannic acid-Fe(III) (TA-Fe) nanoparticles was fabricated by a facile and eco-friendly strategy. The optimal nanocomposite hydrogel showed the good mechanical property and superior processability. More importantly, the nanocomposite hydrogel revealed outstanding photothermal effect, which exhibited a sharp temperature increase of 58 °C during NIR exposure for 10 min. With in vitro antibacterial experiment, the hydrogel could effectively kill of nearly 99 % of bacteria with 10 min of NIR irradiation. Additionally, for the in vivo experiment, the nanocomposite hydrogel could effectively cure wound infection and promote wound healing. Moreover, the hydrogel possessed high biocompatibility. Based on the good mechanical property, outstanding photothermal effect and high biocompatibility, the nanocomposite hydrogel could become a promising antibacterial wound dressings for biomedical applications.

Rheological Investigation of GO Doped p(APTMACl) Composite Hydrogel

The aim of the present work is an approach towards the exploration of comprehension of rheological work on polymer composites synthesized by ex-situ dispersion of graphene oxide (GO) in poly(3-acrylamidopropyl trimethyl ammonium chloride (APTMACl) cationic hydrogel template. FTIR was carried out for confirmation of polymer synthesis and existence of GO in hydrogel network. The rheological investigation via frequency sweep curve (shear measurement) and oscillatory sweep (dynamic mechanical analysis) at different temperature 20, 25, 30, 35, 40 and 45 °C was performed. The storage (G′) and loss (G′′) moduli as a function of angular frequency, yield stress, tangent loss, damping factor and retention property were also studied to confirm the visco-elastomeric nature of the GO@p(APTMACl) composite and their semi solid response at different range of temperature. Various rheological models like Bingham model, modified Bingham model and Ostwald’s power law were applied. The temperature dependency was further tested via Arrhenius-Frenkel-Eyring equation. The sample showed best fitting in the modified Bingham model, which justified the pseudo plastic semi solid behavior of GO@p(APTMACl) composite within the linear visco-elastic region (LVER). All the properties from rheological study show best mechanical property and make the composite hydrogel good for drug delivery and for other environmental applications.

Metal-Organic Framework-Based Chemo-Photothermal Combinational System for Precise, Rapid, and Efficient Antibacterial Therapeutics

Rapid increase of antimicrobial resistance has become an urgent threat to global public health. In this research, since photothermal therapy is a potential antibacterial strategy, which is less likely to cause resistance, a metal-organic framework-based chemo-photothermal combinational system was constructed. Zeolitic imidazolate frameworks-8 (ZIF-8), a porous carrier with unique features such as high loading and pH-sensitive degradation, was synthesized, and then encapsulated photothermal agent indocyanine green (ICG). First, ICG with improved stability in ZIF-8 (ZIF-8-ICG) can effectively produce heat in response to NIR laser irradiation for precise, rapid, and efficient photothermal bacterial ablation. Meanwhile, Zn2+ ions released from ZIF-8 can inhibit bacterial growth by increasing the permeability of bacterial cell membrane and further strengthen photothermal therapy efficacy by reducing the heat resistance of bacteria. Study showed that bacteria suffered from significant changes in morphology after treatment with ZIF-8-ICG under laser irradiation. The combinational chemo-hyperthermia therapy of ZIF-8-ICG could thoroughly ablate murine subcutaneous abscess induced by methicillin-resistant Staphylococcus aureus (MRSA), exhibiting a nearly 100% bactericidal ratio. Both in vitro and in vivo safety evaluation confirmed that ZIF-8-ICG was low toxic. Overall, our researches demonstrated that ZIF-8-ICG has great potential to be served as an alternative to antibiotics in combating multidrug-resistant bacterial pathogens.