Boronic Acid Functionalized Photosensitizers: A Strategy To Target the Surface of Bacteria and Implement Active Agents in Polymer Coatings

Chemically Tailored Single Atoms for Targeted and Light-Controlled Bactericidal Activity

Single-atom (SA) nanoparticles exhibit considerable potential in terms of photothermal properties for bactericidal applications. Nevertheless, the restricted efficacy of their targeted and controlled antibacterial activity has hindered their practical implementation. This study aims to overcome this obstacle by employing chemical modifications to tailor SAs, thereby achieving targeted and light-controlled antimicrobial effects. By conducting atomic-level modifications on palladium SAs using glutathione (GSH) and mercaptophenylboronic acid (MBA), their superior targeted binding capabilities toward Escherichia coli cells are demonstrated, surpassing those of SAs modified with cysteine (Cys). Moreover, these modified SAs effectively inhibit wound bacteria proliferation and promote wound healing in rats, without inducing noticeable toxicity to major organs under 808 nm laser irradiation. This study highlights the significance of chemical engineering in tailoring the antibacterial properties of SA nanoparticles, opening avenues for combating bacterial infections and advancing nanoparticle-based therapies.

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.

Bacteria-Targeting Nanosilver-Based Antibacterial Drugs for Efficient Treatment of Drug-Resistant Bacterial-Infected Keratitis

Keratitis caused by drug-resistant bacteria is a severe condition that can lead to corneal perforation and even blindness, making effective treatment a top priority amid growing antibiotic resistance. Eye drops for anti-inflammatory treatment necessitate frequent administration of high doses throughout every day due to bacterial resistance resulting from antibiotic overuse and the low bioavailability of drugs. To overcome these issues, an antibacterial nanocomposite is prepared via conjugating random copolymers of galactose and 3-(acrylamide)phenylboronic acid to the surface of silver nanoparticles. The customized nanocomposites trigger specific binding to bacteria, resulting in excellent retention of the drug on the ocular surface, resulting in rapid and powerful killing of bacteria and inhibition of bacterial proliferation. Due to its superior drug delivery capabilities to the ocular surface, the functionalized nanocomplex markedly amplifies the anti-inflammatory efficacy, even at low doses. This effect is achieved by impeding immune cell infiltration and diminishing the synthesis of inflammatory mediators and cytokines, thereby suggesting enhanced healing properties for corneal inflammation. This study demonstrates a promising nanocomposite which is an effective and safe antibacterial strategy for bacterial keratitis with favorable prognostic and clinical conversion potential.

Metal-Based Photosensitizers as Inducers of Regulated Cell Death Mechanisms

Over the last few decades, various forms of regulated cell death (RCD) have been discovered and were found to improve cancer treatment. Although there are several reviews on RCD induced by photodynamic therapy (PDT), a comprehensive summary covering metal-based photosensitizers (PSs) as RCD inducers has not yet been presented. In this review, we systematically summarize the works on metal-based PSs that induce different types of RCD, including ferroptosis, immunogenic cell death (ICD), and pyroptosis. The characteristics and mechanisms of each RCD are explained. At the end of each section, a summary of the reported commonalities between different metal-based PSs inducing the same RCD is emphasized, and future perspectives on metal-based PSs inducing novel forms of RCD are discussed at the end of the review. Considering the essential roles of metal-based PSs and RCD in cancer therapy, we hope that this review will provide the stage for future advances in metal-based PSs as RCD inducers.

Rapid detection of Saccharomyces cerevisiae with boronic acid-decorated multivariate metal-organic frameworks and aptamers

Liquor brewing is a classic solid-substrate fermentation process with a unique brewing microbiome. As one of the most common fungi, Saccharomyces cerevisiae ferments saccharides and has been extensively applied in brewing production. Here, we present the facile fabrication of a selective, sensitive, and integrated fluorescent biosensor for S. cerevisiae detection. The proposed biosensor used aptamer-modified magnetic beads to specifically capture S. cerevisiae, and the enriched fungi were recognized and detected with boronic acid-decorated multivariate metal-organic frameworks. The biosensor allows rapid quantification of S. cerevisiae in the range of 10-106 CFU mL-1, showing excellent specificity and repeatability, and maintaining stable biosensing performance in long-term storage. The analytical ability of the proposed biosensor was successfully verified in distilled yeast and fermented grain samples spiked with S. cerevisiae.

Photothermal-driven disassembly of naphthalocyanine nano-photosensitizers for photothermal and photodynamic therapy

The disassembly of nanomaterials is of particular interest for high-quality imaging and targeted therapies in the field of nanomedicine. In this study, we developed a novel strategy for fabricating self-assembled naphthalocyanine photosensitizers (SiNc@CEL) with intrinsically unique photochemical and photophysical properties. SiNc@CEL could be disassembled under the photothermal effect, and its photoactivity could be enhanced by 780 nm laser irradiation. Moreover, SiNc@CEL generates reactive oxygen species, including superoxide radicals (O₂^•-) and singlet oxygen (¹O₂), as well as good photothermal properties, facilitating the application of multifunctional phototherapy. In vitro evaluation indicated that SiNc@CEL possesses an excellent bactericidal effect under a combination of photodynamic (PDT) and photothermal therapy (PTT). The in vivo treatment of a full-layer skin defect model of Escherichia coli (E. coli) infection showed that SiNc@CEL had superior antibacterial and wound-healing abilities. These results provide the basis for a feasible strategy to enhance the phototherapeutic effect of photosensitizer (PS) systems.

Structural optimization of BODIPY photosensitizers for enhanced photodynamic antibacterial activities

Enhancing the interactions between photosensitizers and bacteria is key to developing effective photodynamic antibacterial agents. However, the influence of different structures on the therapeutic effects has not been systematically investigated. Herein, 4 BODIPYs with distinct functional groups, including the phenylboronic acid (PBA) group and pyridine (Py) cations, were designed to explore their photodynamic antibacterial activities. The BODIPY with the PBA group (IBDPPe-PBA) exhibits potent activity against planktonic Staphylococcus aureus (S. aureus) upon illumination, while the BODIPY with Py cations (IBDPPy-Ph) or both the PBA group and Py cations (IBDPPy-PBA) can significantly minimize the growth of both S. aureus and Escherichia coli (E. coli). In particular, IBDPPy-Ph can not only eliminate the mature S. aureus biofilm and E. coli biofilm in vitro, but also promote the healing of the infected wound. Our work provides an alternative for reasonable design of photodynamic antibacterial materials.

Direct discrimination of cell surface glycosylation signatures using a single pH-responsive boronic acid-functionalized polymer

Cell surface glycans serve fundamental roles in many biological processes, including cell-cell interaction, pathogen infection, and cancer metastasis. Cancer cell surface have alternative glycosylation to healthy cells, making these changes useful hallmarks of cancer. However, the diversity of glycan structures makes glycosylation profiling very challenging, with glycan 'fingerprints' providing an important tool for assessing cell state. In this work, we utilized the pH-responsive differential binding of boronic acid (BA) moieties with cell surface glycans to generate a high-content six-channel BA-based sensor array that uses a single polymer to distinguish mammalian cell types. This sensing platform provided efficient discrimination of cancer cells and readily discriminated between Chinese hamster ovary (CHO) glycomutants, providing evidence that discrimination is glycan-driven. The BA-functionalized polymer sensor array is readily scalable, providing access to new diagnostic and therapeutic strategies for cell surface glycosylation-associated diseases.

Quaternary Ammonium-Tethered Phenylboronic Acids Appended Supramolecular Nanomicelles as a Promising Bacteria Targeting Carrier for Nitric Oxide Delivery

The delivery of drugs to focal sites is a central goal and a key challenge in the development of nanomedicine carriers. This strategy can improve the selectivity and bioavailability of the drug while reducing its toxicity. To ensure the specific release of nitric oxide at the site of a bacterial infection without damaging the surrounding normal tissue, we designed a host-guest molecule containing a host molecule with a target moiety and a nitric oxide donor to release nitric oxide. The boronic acid group in the structure of this nanoparticle interacts strongly and specifically with the surface of E. coli. In addition, the quaternary amine salt can interact electrostatically with bacteria, indicating a large number of negatively charged cell membranes; altering the molecular structure of the cell membrane; increasing the permeability of the cell membrane; and causing cytoplasmic diffusion and cell lysis, resulting in lethal activity against most bacteria. The synthesised molecules were characterised by ¹H NMR and mass spectrometry. The strong specific interaction of the boronic acid moiety with the surface of E. coli and the electrostatic interaction of the quaternary amine salt with the cell membrane were confirmed by antibacterial experiments on molecules with and without the targeting moiety. The targeting group-modified micelles enhanced the antibacterial effect of the micelles very effectively through specific interactions and electrostatic interactions. In addition, in vitro skin wound healing experiments also confirmed the targeting and antimicrobial effect of micelles. These results suggest that the specific release of nitric oxide at the site of bacterial infection is an important guide to further address the emergence of antibiotic-resistant strains of bacteria.

Photodynamic Hydrogen-Bonded Biohybrid Framework: A Photobiocatalytic Cascade Nanoreactor for Accelerating Diabetic Wound Therapy

A diabetic wound causes thousands of infections or deaths around the world each year, and its healing remains a critical challenge because of the ease of multidrug-resistant (MDR) bacterial infection, as well as the intrinsic hyperglycemic and hypoxia microenvironment that inhibits the therapeutic efficiency. Herein, we pioneer the design of a photobiocatalytic cascade nanoreactor via spatially organizing the biocatalysts and photocatalysts utilizing a hydrogen-bonded organic framework (HOF) scaffold for diabetic wound therapy. The HOF scaffold enables it to disperse and stabilize the host cargos, and the formed long-range-ordered mesochannels also facilitate the mass transfer that enhances the cascade activity. This integrated HOF nanoreactor allows the continuous conversion of overexpressed glucose and H₂O₂ into toxic reactive oxygen species by the photobiocatalytic cascade. As a result, it readily reverses the microenvironment of the diabetes wound and exhibits an extraordinary capacity for wound healing through synergistic photodynamic therapy. This work describes the first example of constructing an all-in-one HOF bioreactor for antimicrobial diabetes wound treatment and showcases the promise of combined biocatalysis and photocatalysis achieved by using an HOF scaffold in biomedicine applications.

Supramolecular Adhesive Materials with Antimicrobial Activity for Emerging Biomedical Applications

Traditional adhesives or glues such as cyanoacrylates, fibrin glue, polyethylene glycol, and their derivatives have been widely used in biomedical fields. However, they still suffer from numerous limitations, including the mechanical mismatch with biological tissues, weak adhesion on wet surfaces, biological incompatibility, and incapability of integrating desired multifunction. In addition to adaptive mechanical and adhesion properties, adhesive biomaterials should be able to integrate multiple functions such as stimuli-responsiveness, control-releasing of small or macromolecular therapeutic molecules, hosting of various cells, and programmable degradation to fulfill the requirements in the specific biological systems. Therefore, rational molecular engineering and structural designs are required to facilitate the development of functional adhesive materials. This review summarizes and analyzes the current supramolecular design strategies of representative adhesive materials, serving as a general guide for researchers seeking to develop novel adhesive materials for biomedical applications.

Photodynamic inactivation of pathogenic Gram-negative and Gram-positive bacteria mediated by Si(IV) phthalocyanines bearing axial ammonium units

The photodynamic inactivation (PDI) of microorganisms has gained interest as an efficient option for conventional antibiotic treatments. Recently, Si(IV) phthalocyanines (SiPcs) have been highlighted as promising photosensitizers (PSs) to the PDI of microorganisms due to their remarkable absorption and emission features. To increase the potential of cationic SiPcs as PS drugs, one novel (1a) and two previously described (2a and 3a) axially substituted PSs with di-, tetra-, and hexa-ammonium units, respectively, were synthesized and characterized. Their PDI effect was evaluated for the first time against Escherichia coli and Staphylococcus aureus, a Gram-negative and a Gram-positive bacterium, respectively. The photodynamic treatments were conducted with PS concentrations of 3.0 and 6.0 μM under 60 min of white light irradiation (150 mW.cm^-2). The biological results show high photodynamic efficiency for di- and tetra-cationic PSs 1a and 2a (6.0 μM), reducing the E. coli viability in 5.2 and 3.9 log, respectively (after 15 min of dark incubation before irradiation). For PS 3a, a similar bacterial reduction (3.6 log) was achieved but only with an extended dark incubation period (30 min). Under the same experimental conditions, the photodynamic effect of cationic PSs 1a-3a on S. aureus was even more promising, with abundance reductions of ca. 8.0 log after 45-60 min of PDI treatment. These results reveal the high PDI efficiency of PSs bearing ammonium groups and suggest their promising application as a broad-spectrum antimicrobial to control infections caused by Gram-negative and Gram-positive bacteria.

Antibacterial Photodynamic Therapy in the Near-Infrared Region with a Targeting Antimicrobial Peptide Connected to a π-Extended Porphyrin

The increase of antimicrobial resistance to conventional antibiotics is worldwide a major health problem that requires the development of new bactericidal strategies. Antimicrobial photodynamic therapy (a-PDT) that generates reactive oxygen species acting on multiple cellular targets is unlikely to induce bacterial resistance. This localized treatment requires, for safe and efficient treatment of nonsuperficial infections, a targeting photosensitizer excited in the near IR. To this end, a new conjugate consisting of an antimicrobial peptide linked to a π-extended porphyrin photosensitizer was designed for a-PDT. Upon irradiation at 720 nm, the conjugate has shown at micromolar concentration strong bactericidal action on both Gram-positive and Gram-negative bacteria. Moreover, this conjugate allows one to reach a low minimum bactericidal concentration with near IR excitation without inducing toxicity to skin cells.

NIR-activated nanosystems with self-modulated bacteria targeting for enhanced biofilm eradication and caries prevention

The efficacious delivery of antimicrobial drugs to intractable oral biofilms remains a challenge due to inadequate biofilm penetration and lack of pathogen targeting. Herein, we have developed a microenvironment-activated poly(ethylene glycol) (PEG)-sheddable nanoplatform to mediate targeted delivery of drugs into oral biofilms for the efficient prevention of dental caries. The PEGylated nanoplatform with enhanced biofilm penetration is capable of deshielding the PEG layer under slightly acidic conditions in a PEG chain length-dependent manner to re-expose the bacteria-targeting ligands, thereby facilitating targeted codelivery of ciprofloxacin (CIP) and IR780 to the bacteria after accumulation within biofilms. The nanoplatform tends to induce bacterial agglomeration and suffers from degradation in the acidic oral biofilm microenvironment, triggering rapid drug release on demand around bacterial cells. The self-modulating nanoplatform under near-infrared (NIR) irradiation accordingly displays greatly augmented potency in oral biofilm penetration and disruption compared with drugs alone. Topical oral treatment with nanoplatforms involving synergetic pharmacological and photothermal/photodynamic trinary therapy results in robust biofilm dispersion and efficacious suppression of severe tooth decay in rats. This versatile nanoplatform can promote local accumulation and specific drug transport into biofilms and represents a new paradigm for targeted drug delivery for the management of oral biofilm-associated infections.

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A targeted drug delivery system was developed to scavenge oral biofilms and prevent dental caries.

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The system is activated by pH gradient to modulate biofilm penetration, bacterial anchorage and drug release.

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The system demonstrated significant efficacy in preventing dental caries under a multimodal treatment regimen.

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This strategy is expected to be applied to control a range of oral biofilm-associated infections.

Boronic acid chemistry for fluorescence-based quantitative DNA sensing

Contrary to the long-standing opinion of boronic acids being typically reactive with 1,2- and 1,3-diols and hence not suitable for quantitative sensing of DNA containing only a mono-ol unit, this proof-of-concept study has successfully shown the feasibility to quantitatively detect DNA in the concentration range of 5 to 50 nM plausibly through boronic acid-mediated bridging of two DNA double helices via the 3' hydroxy groups, which opens up new avenues in the realm of oligonucleotide biochemistry.

Boronic Acid-Decorated Multivariate Photosensitive Metal-Organic Frameworks for Combating Multi-Drug-Resistant Bacteria

Metal-organic frameworks (MOFs) are promising photosensitized materials that have displayed great advantages in antibacterial application. However, their bactericidal activity is still limited by the ultrashort diffusion distance of biocidal reactive oxygen species (ROS). Herein, we integrate the bacterial-binding boronic acid ligand and photosensitized porphyrin into one single MOF, synergistically boosting antibiotic capability. The introduction of the boronic acid group with a closed physical gap makes multivariate MOFs more powerful for eradicating multi-drug-resistant (MDR) bacteria. The MOFs that are decorated with boronic acid possess antibacterial efficiencies (10-20 times) higher than those without the targeting ligand. Moreover, the MOFs exhibit excellent biocompatibility. They significantly decrease the inflammatory responses and accelerate the healing of chronic wounds infected with MDR bacteria (nearly 2 times faster). This work provides a strategy to develop multivariate MOFs that target bacteria, which will further inspire specific bacterial-binding therapy in the future.

Organic photosensitizers for antimicrobial phototherapy

Microbial infectious diseases, especially those caused by new and antibiotic-resistant pathogenic microbes, have become a significant threat to global human health. As an antibiotic-free therapy, phototherapy is a promising approach to treat microbial infections due to its spatiotemporal selectivity, non-invasiveness, minimal side effects, and broad antimicrobial spectrum. Although organic photosensitizer-based antimicrobial phototherapy has been extensively studied over the last decade, there has been no specific review article on this topic yet. It is important and timely to summarize recent research progress in this field. This tutorial review highlights the concept and significance of phototherapy and summarizes innovative types of organic photosensitizers with design strategies to deal with microbial infections. In addition, examples of organic antimicrobial photosensitizers, including antibacterial photosensitizers, antiviral photosensitizers, and antifungal photosensitizers are discussed. Finally, current challenges and future directions of organic photosensitizer-based phototherapy for clinical antimicrobial applications are presented. We believe that this tutorial review will provide general guidance for the future development of efficient photosensitizers and encourage preclinical and clinical studies for phototherapy-mediated antimicrobial treatments.

Influence of photosensitizer concentration and polymer composition on photoinduced antimicrobial activity of PVA- and PVA-chitosan-based electrospun nanomaterials cross-linked with tailor-made silicon(IV) phthalocyanine

The ongoing effort to eradicate pathogenic bacteria and viruses is a major endeavor that requires development of new and innovative materials. Materials based on photodynamic action represent an emerging and attractive area of research, and therefore, a broad understanding of chemical design principles is required. In the present study, we investigated the antibacterial and antiviral activities of five different nanofibrous membranes composed of poly(vinyl alcohol) or poly(vinyl alcohol)-chitosan mixture cross-linked through silicon(IV)phthalocyanine derivative with the aim to identify the role of the carrier polymer and photosensitizers concentration on its efficacy. A straightforward cross-linking process was adopted to create a water-stable material with an almost uniform distribution of the fiber structure, as revealed by scanning electron microscopy. The results of the antimicrobial studies showed that the increase in the amount of chitosan in the polymer mixture, rather than the increase in the photosensitizer concentration, enhanced the activity of the material. Due to their visible light-triggered antimicrobial activity, the resulting materials provide valuable opportunities for both topical antimicrobial photodynamic therapy and the area of environmental remediation.

Stimuli-Responsive Antibacterial Materials: Molecular Structures, Design Principles, and Biomedical Applications

Infections are regarded as the most severe complication associated with human health, which are urgent to be solved. Stimuli-responsive materials are appealing therapeutic platforms for antibacterial treatments, which provide great potential for accurate theranostics. In this review, the advantages, the response mechanisms, and the key design principles of stimuli-responsive antibacterial materials are highlighted. The biomedical applications, the current challenges, and future directions of stimuli-responsive antibacterial materials are also discussed. First, the categories of stimuli-responsive antibacterial materials are comprehensively itemized based on different sources of stimuli, including external physical environmental stimuli (e.g., temperature, light, electricity, salt, etc.) and bacterial metabolites stimuli (e.g., acid, enzyme, redox, etc.). Second, structural characteristics, design principles, and biomedical applications of the responsive materials are discussed, and the underlying interrelationships are revealed. The molecular structures and design principles are closely related to the sources of stimuli. Finally, the challenging issues of stimuli-responsive materials are proposed. This review will provide scientific guidance to promote the clinical applications of stimuli-responsive antibacterial materials.

Biomimetic Nanomedicine-Triggered in Situ Vaccination for Innate and Adaptive Immunity Activations for Bacterial Osteomyelitis Treatment

The development of bacterial vaccines for inducing an immunoresponse against infectious diseases such as osteomyelitis is of great significance and importance. However, the responsiveness of bacterial immunotherapy remains far from being satisfactory, largely due to the erratic antigen epitopes of bacteria. Herein, we report an in situ vaccination strategy for the immunotherapy of bacterial infection based on an osteomyelitis model using a biomimetic nanomedicine named as HMMP, which was constructed by engineering PpIX-encapsulated hollow MnO_x with a hybrid membrane exfoliated from both macrophage and tumor cell lines. The as-established HMMP features a burst bacterial antigen release as the in situ vaccine by the augmented sonodynamic treatment and the resultant priming of antigen-presenting cells for the following activations of both cellular and humoral adaptive immunities against bacterial infections. This treatment regimen not only triggers initial bacterial regression in the established osteomyelitis model but also simultaneously generates robust systemic antibacterial immunity against poorly immunogenic secondary osteomyelitis in the contralateral knee and additionally confers long-lasting bacteria-specific immune memory responses to prevent infection relapse. Thus, our study provides a proof of concept of in situ vaccination for the activation of both innate and adaptive antibacterial immune responses, providing an individual-independent bacterial immunotherapy.

Recent Advances in Nanozymes for Bacteria-Infected Wound Therapy

Bacterial-infected wounds are a serious threat to public health. Bacterial invasion can easily delay the wound healing process and even cause more serious damage. Therefore, effective new methods or drugs are needed to treat wounds. Nanozyme is an artificial enzyme that mimics the activity of a natural enzyme, and a substitute for natural enzymes by mimicking the coordination environment of the catalytic site. Due to the numerous excellent properties of nanozymes, the generation of drug-resistant bacteria can be avoided while treating bacterial infection wounds by catalyzing the sterilization mechanism of generating reactive oxygen species (ROS). Notably, there are still some defects in the nanozyme antibacterial agents, and the design direction is to realize the multifunctionalization and intelligence of a single system. In this review, we first discuss the pathophysiology of bacteria infected wound healing, the formation of bacterial infection wounds, and the strategies for treating bacterially infected wounds. In addition, the antibacterial advantages and mechanism of nanozymes for bacteria-infected wounds are also described. Importantly, a series of nanomaterials based on nanozyme synthesis for the treatment of infected wounds are emphasized. Finally, the challenges and prospects of nanozymes for treating bacterial infection wounds are proposed for future research in this field.

Regulation of photo triggered cytotoxicity in electrospun nanomaterials: role of photosensitizer binding mode and polymer identity

Although electrospun nanomaterials containing photoactive dyes currently compete with the present state of art antimicrobial materials, relatively few structure-activity relationships have been established to identify the role of carrier polymer and photosensitizer binding mode on the performance of the materials. In this study scaffolds composed of poly(vinyl alcohol), polyacrylonitrile, poly(caprolactone), and tailor-made phthalocyanine-based photosensitizers are developed utilizing electrospinning as a simple, time and cost-effective method. The photoinduced activity of nanofibrous materials was characterized in vitro against E. coli and B. subtilis as models for Gram-negative and Gram-positive bacteria respectively, as well as against bacteriophages phi6 and MS2 as models for enveloped and non-enveloped viruses respectively. For the first time, we show how polymer-specific properties affect antifouling and antimicrobial activity of the nanofibrous material, indicating that the most promising way to increase efficiency is likely via methods that focus on increasing the number of short, but strong and reversible bacteria-surface interactions.

Potentiation Effect of Iodine Species on the Antimicrobial Capability of Surfaces Coated with Electroactive Phthalocyanines

The spreading of different infections can occur through direct contact with glass surfaces in commonly used areas. Incorporating the use of alternative therapies in these materials seems essential to reduce and also avoid bacterial resistance. In this work, the capability to kill microbes of glass surfaces coated with two electroactive metalated phthalocyanines (ZnPc-EDOT and CuPc-EDOT) is assessed. The results show that both of these materials are capable of producing reactive oxygen species; however, the polymer with Zn(II) (ZnPc-PEDOT) has a singlet oxygen quantum yield 8-fold higher than that of the Cu(II) containing analogue. This was reflected in the in vitro experiments where the effectiveness of the surfaces was tested in bacterial suspensions, monitoring single microbe inactivation upon attachment to the polymers, and eliminating mature biofilms. Furthermore, we evaluated the use of an inorganic salt (KI) to potentiate the photodynamic inactivation mediated by an electropolymerized surface. The addition of the salt improved the efficiency of phototherapy at least two times for both polymers; nevertheless, the material coated with ZnPc-PEDOT was the only one capable of eliminating >99.98% of the initial microbes loading under different circumstances.

Tug-of-War between Covalent Binding and Electrostatic Interaction Effectively Killing E. coli without Detectable Resistance

Antimicrobial resistance in Gram-negative bacteria has become one of the leading causes of morbidity and mortality and a serious worldwide public health concern due to the fact that Gram-negative bacteria have an additional outer membrane protecting them from an unwanted compound invading. It is still very difficult for antimicrobials to reach intracellular targets and very challenging to treat Gram-negative bacteria with the current strategies. Here, we found that (o-(bromomethyl)phenyl)boronic acid was incorporated into poly((2-N,N-diethyl)aminoethyl acrylate) (PDEA), forming a copolymer (poly(o-B_n-DEA)) having both phenylboronic acid (B) and ((2-N,N-diethyl)amino) (DEA) units. Poly(o-B_n-DEA) exhibits very strong intramolecular B-N coordination, which could highly promote the covalent binding of phenylboronic acid with lipopolysaccharide (LPS) on the outer membrane of E. coli and lodge poly(o-B_n-DEA) on the LPS layer on the surface of E. coli. Meanwhile, the strong electrostatic interaction between poly(o-B_n-DEA) and the negatively charged lipid preferred tugging the poly(o-B_n-DEA) into the lipid bilayer of E. coli. The combating interactions between covalent binding and electrostatic interaction form a tug-of-war action, which could trigger the lysis of the outer membrane, thereby killing Gram-negative E. coli effectively without detectable resistance.

Recent Strategies to Develop Innovative Photosensitizers for Enhanced Photodynamic Therapy

This review presents a robust strategy to design photosensitizers (PSs) for various species. Photodynamic therapy (PDT) is a photochemical-based treatment approach that involves the use of light combined with a light-activated chemical, referred to as a PS. Attractively, PDT is one of the alternatives to conventional cancer treatment due to its noninvasive nature, high cure rates, and low side effects. PSs play an important factor in photoinduced reactive oxygen species (ROS) generation. Although the concept of photosensitizer-based photodynamic therapy has been widely adopted for clinical trials and bioimaging, until now, to our surprise, there has been no relevant review article on rational designs of organic PSs for PDT. Furthermore, most of published review articles in PDT focused on nanomaterials and nanotechnology based on traditional PSs. Therefore, this review aimed at reporting recent strategies to develop innovative organic photosensitizers for enhanced photodynamic therapy, with each example described in detail instead of providing only a general overview, as is typically done in previous reviews of PDT, to provide intuitive, vivid, and specific insights to the readers.

Organic Photo-antimicrobials: Principles, Molecule Design, and Applications

The emergence of multi-drug-resistant pathogens threatens the healthcare systems world-wide. Recent advances in phototherapy (PT) approaches mediated by photo-antimicrobials (PAMs) provide new opportunities for the current serious antibiotic resistance. During the PT treatment, reactive oxygen species or heat produced by PAMs would react with the cell membrane, consequently leaking cytoplasm components and effectively eradicating different pathogens like bacteria, fungi, viruses, and even parasites. This Perspective will concentrate on the development of different organic photo-antimicrobials (OPAMs) and their application as practical therapeutic agents into therapy for local infections, wound dressings, and removal of biofilms from medical devices. We also discuss how to design highly efficient OPAMs by modifying the chemical structure or conjugating with a targeting component. Moreover, this Perspective provides a discussion of the general challenges and direction for OPAMs and what further needs to be done. It is hoped that through this overview, OPAMs can prosper and will be more widely used for microbial infections in the future, especially at a time when the global COVID-19 epidemic is getting more serious.

Umbelliferone Decorated Water-soluble Zinc(II) Phthalocyanines - In Vitro Phototoxic Antimicrobial Anti-cancer Agents

In this contribution we report on the synthesis, characterization and application of water-soluble zinc(II) phthalocyanines, which are decorated with four or eight umbelliferone moieties for photodynamic therapy (PDT). These compounds are linked peripherally to zinc(II) phthalocyanine by a triethylene glycol linker attached to pyridines, leading to cationic pyridinium units, able to increase the water solubility of the system. Beside their photophysical properties they were analyzed concerning their cellular distribution in human hepatocyte carcinoma (HepG2) cells as well as their phototoxicity towards HepG2 cells, Gram-positive (S. aureus strain 3150/12 and B. subtilis strain DB104) and Gram-negative bacteria (E. coli strain UTI89 and E. coli strain Nissle 1917). At low light doses and concentrations, they exhibit superb antimicrobial activity against Gram-positive bacteria as well as anti-tumor activity against HepG2. They are even capable to inactivate Gram-negative bacteria, whereas the dark toxicity remains low. These unique water-soluble compounds can be regarded as all-in-one type photosensitizers with broad applications ranges in the future.

Self-Assembled Porphyrinoids: One-Component Nanostructured Photomedicines

Photodynamic therapy (PDT) is becoming a promising way to treat various kinds of cancers, with few side effects. Porphyrinoids are the most relevant photosensitizers (PS) in PDT, because they present high extinction coefficients, biocompatibility, and excellent photochemical behavior. To maximize therapeutic effects, polymer-PS conjugates, and PS-loaded nanoparticles have been developed, with insights in improving tumor delivery. However, some drawbacks such as non-biodegradability, multistep fabrication, and low reagent loadings limit their clinical application. A novel strategy, noted by some authors as the "one-for-all" approach, is emerging to circumvent the use of additional delivery agents. This approach relies on the self-assembly of amphiphilic PS to fabricate nanostructures with improved transport properties. In this review we focus on different rational designs of porphyrinoid PS to achieve some of the following attributes in nanoassembly: i) selective uptake, through the incorporation of recognizable biological vectors; ii) responsiveness to stimuli; iii) combination of imaging and therapeutic functions; and iv) multimodal therapy, including photothermal or chemotherapy abilities.

Injectable stress relaxation gelatin-based hydrogels with positive surface charge for adsorption of aggrecan and facile cartilage tissue regeneration

Background

Cartilage injury and pathological degeneration are reported in millions of patients globally. Cartilages such as articular hyaline cartilage are characterized by poor self-regeneration ability due to lack of vascular tissue. Current treatment methods adopt foreign cartilage analogue implants or microfracture surgery to accelerate tissue repair and regeneration. These methods are invasive and are associated with the formation of fibrocartilage, which warrants further exploration of new cartilage repair materials. The present study aims to develop an injectable modified gelatin hydrogel.

Method

The hydrogel effectively adsorbed proteoglycans secreted by chondrocytes adjacent to the cartilage tissue in situ, and rapidly formed suitable chondrocyte survival microenvironment modified by ε-poly-L-lysine (EPL). Besides, dynamic covalent bonds were introduced between glucose and phenylboronic acids (PBA). These bonds formed reversible covalent interactions between the cis−diol groups on polyols and the ionic boronate state of PBA. PBA-modified hydrogel induced significant stress relaxation, which improved chondrocyte viability and cartilage differentiation of stem cells. Further, we explored the ability of these hydrogels to promote chondrocyte viability and cartilage differentiation of stem cells through chemical and mechanical modifications.

Results

In vivo and in vitro results demonstrated that the hydrogels exhibited efficient biocompatibility. EPL and PBA modified GelMA hydrogel (Gel-EPL/B) showed stronger activity on chondrocytes compared to the GelMA control group. The Gel-EPL/B group induced the secretion of more extracellular matrix and improved the chondrogenic differentiation potential of stem cells. Finally, thus hydrogel promoted the tissue repair of cartilage defects.

Conclusion

Modified hydrogel is effective in cartilage tissue repair.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00950-0.

The Rise of Silicon Phthalocyanine: From Organic Photovoltaics to Organic Thin Film Transistors

Silicon phthalocyanines are emerging n-type semiconductors for use in organic photovoltaics (OPVs) and organic thin-film transistors (OTFTs). Their low synthetic complexity paired with their versatile axial group facilitates the fine-tuning of their chemical properties, solution properties and processing characteristics without significantly affecting their frontier orbital levels or their absorption properties. The crystal engineering and film forming characteristics of silicon phthalocyanine semiconductors can be tuned through appropriate axial group functionalization, therefore facilitating their integration into both OTFTs and OPVs by solution processing or vapor deposition. This Spotlight on Applications will discuss recent advances in the integration of this exciting class of phthalocyanine into OTFTs and OPVs and highlights their promising future.

Mechano-Induced Assembly of a Nanocomposite for "Press-N-Go" Coatings with Highly Efficient Surface Disinfection

Using antimicrobial coatings to control the spread of pathogenic microbes is appreciated in public and healthcare settings, but the performance of most antimicrobial coatings could not fulfill the increasing requirements, particularly the ease of preparation, high durability, rapid response, and high killing efficiency. Herein, we develop a new type of mechano-induced assembly of nanocomposite coating by simple "Press-N-Go" procedures on various substrates such as glassware, gloves, and fabrics, in which the coating shows strong adhesion, high shear stability, and high stiffness, making it durable in daily use to withstand common mechanical deformation and scratches. The coating also shows remarkable disinfection effectiveness over 99.9% to clinically significant multiple drug-resistant bacterial pathogens upon only 6 s near-infrared irradiation, which can be further improved to over 99.9999% upon another 6 s treatment. We envision that the coating can provide convenience and values to control pathogen spread for easily contaminated substrates in high-risk areas.

The Antibacterial Effects of Supermolecular Nano-Carriers by Combination of Silver and Photodynamic Therapy

The over-use of antibiotics has promoted multidrug resistance and decreased the efficacy of antibiotic therapy. Thus, it is still in great need to develop efficient treatment strategies to combat the bacteria infection. The antimicrobial photodynamic therapy (aPDT) and silver nanoparticles have been emerged as effective antibacterial methods. However, the silver therapy may induce serious damages to human cells at high concentrations and, the bare silver nanoparticles may rapidly aggregate, which would reduce the antibacterial efficacy. The encapsulation of sliver by nano-carrier is a promising way to avoid its aggregation and facilitates the co-delivery of drugs for combination therapy, which does not require high concentration of sliver to exert antibacterial efficacy. This work constructed a self-assembled supermolecular nano-carrier consisting of the photosensitizers (PSs), the anti-inflammatory agent and silver. The synthesized supermolecular nano-carrier produced reactive oxygen species (ROS) under the exposure of 620-nm laser. It exhibited satisfying biocompatibility in L02 cells. And, this nano-carrier showed excellent antibacterial efficacy in Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) as indicated by bacterial growth and colony formation. Its antibacterial performance is further validated by the bacteria morphology through the scanning electron microscope (SEM), showing severely damaged structures of bacteria. To summary, the supermolecular nano-carrier TCPP-MTX-Ag-NP combining the therapeutic effects of ROS and silver may serve as a novel strategy of treatment for bacterial infection.

SERS imaging analyses of bacteria cells among plant tissues

A chemical imaging method to mass surveil bacteria cells among plant tissues in situ is reported. Bacteria cells were pre-labeled with 3-mercaptophenylboronic acid for complexation with gold nanoparticles. Surface-enhanced Raman spectra were collated en masse to generate panoramic chemical images of bacteria populations. The approach was successfully employed to study the distribution of mass bacteria populations directly on and in selected plant tissues. This study demonstrates the great potential with which SERS imaging can be utilized for the study of bacterial cells among complex matrices, in some ways that are superior to electron and fluorescent microscopies.

Turning Photons into Drugs: Phthalocyanine-Based Photosensitizers as Efficient Photoantimicrobials

One of the most promising alternatives for treating bacterial infections is antimicrobial photodynamic therapy (aPDT), making the synthesis and application of new photoactive compounds called photosensitizers (PS) a dynamic research field. In this regard, phthalocyanine (Pc) derivatives offer great opportunities due to their extraordinary light-harvesting and tunable electronic properties, structural versatility, and stability. This Review, rather than focusing on synthetic strategies, intends to overview current progress in the structural design strategies for Pcs that could achieve effective photoinactivation of microorganisms. In addition, the Review provides a concise look into the recent developments and applications of nanocarrier-based Pc delivery systems.

π-Extended Donor-Acceptor Porphyrins and Metalloporphyrins for Antimicrobial Photodynamic Inactivation

Free base, zinc and palladium π‐extended porphyrins containing fused naphthalenediamide units were employed as photosensitizers in antimicrobial photodynamic therapy (aPDT). Their efficacy, assessed by photophysical and in vitro photobiological studies on Gram‐positive bacteria, was found to depend on metal coordination, showing a dramatic enhancement of photosensitizing activity for the palladium complex.

Facile Fabrication of Silicon(IV)Phthalocyanine-Embedded Poly(vinyl alcohol)-Based Antibacterial and Antifouling Interfaces

Interest in the photodynamic inactivation of bacteria as an alternative method to antibiotic treatment continues to grow. Based on this approach, light-activated anti-infective interfaces could be fabricated via incorporation of photosensitizers into the polymer-based materials. In order to combine photobactericidal and antifouling functions, the choice of the carrier polymer is of particular significance: it should enable fast and effective conjugation of photosensitizer and reduce the formation of bioburden on the artificial material in a biological environment. This study reports one-pot fabrication and characterization of two silicon(IV)phthalocyanine /poly(vinyl alcohol)-based electrospun mats. The method relies on the thermal cross-linking of components by esterification using sebacic acid as a cross-linking agent. Fabricated flexible mats showed photosensitizer-dependent antibacterial photoactivity against different Gram-positive bacteria with low cytotoxic effects on human fibroblasts and were effective against bacterial attachment, as an early step toward future biofilm formation. This work provides practical guidelines in developing photoactive materials and interfaces that can be used in nonadhesive wound dressings, food packaging, water, and air filtration.

Functionalized biomaterials to combat biofilms

Pathogenic microbial biofilms that readily form on implantable medical devices or human tissues have posed a great threat to worldwide healthcare. Hopes are focused on preventive strategies towards biofilms, leaving a thought-provoking question: how to tackle the problem of established biofilms? In this review, we briefly summarize the functionalized biomaterials to combat biofilms and highlight current approaches to eradicate pre-existing biofilms. We believe that all of these strategies, alone or in combination, could represent a blueprint for fighting biofilm-associated infections in the postantibiotic era.

A boronic acid-functionalized phthalocyanine with an aggregation-enhanced photodynamic effect for combating antibiotic-resistant bacteria

Most existing photosensitizers (e.g., porphyrins) are often aggregated in aqueous solution because of their large conjugated molecular structures. This aggregation usually results in a lack or low levels of reactive oxygen species (ROS) generation due to aggregation-caused quenching, which severely hampers the application of photosensitizers in photodynamic therapy (PDT). Herein, we make an interesting finding that a boronic acid-functionalized phthalocyanine (PcN4-BA) displays an uncommon phenomenon, an aggregation-enhanced photodynamic effect. The combination of the ability to form uniform nanostructured self-assemblies in water, highly efficient ROS generation and boronic acid-induced targeting give PcN4-BA excellent performances in antimicrobial PDT.

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

Background

Infectious diseases caused by multidrug-resistant (MDR) bacteria, especially MDR Gram-negative strains, have become a global public health challenge. Multifunctional nanomaterials for controlling MDR bacterial infections via eradication of planktonic bacteria and their biofilms are of great interest.

Results

In this study, we developed a multifunctional platform (TG-NO-B) with single NIR laser-triggered PTT and NO release for synergistic therapy against MDR Gram-negative bacteria and their biofilms. When located at the infected sites, TG-NO-B was able to selectively bind to the surfaces of Gram-negative bacterial cells and their biofilm matrix through covalent coupling between the BA groups of TG-NO-B and the bacterial LPS units, which could greatly improve the antibacterial efficiency, and reduce side damages to ambient normal tissues. Upon single NIR laser irradiation, TG-NO-B could generate hyperthermia and simultaneously release NO, which would synergistically disrupt bacterial cell membrane, further cause leakage and damage of intracellular components, and finally induce bacteria death. On one hand, the combination of NO and PTT could largely improve the antibacterial efficiency. On the other hand, the bacterial cell membrane damage could improve the permeability and sensitivity to heat, decrease the photothermal temperature and avoid damages caused by high temperature. Moreover, TG-NO-B could be effectively utilized for synergistic therapy against the in vivo infections of MDR Gram-negative bacteria and their biofilms and accelerate wound healing as well as exhibit excellent biocompatibility both in vitro and in vivo.

Conclusions

Our study demonstrates that TG-NO-B can be considered as a promising alternative for treating infections caused by MDR Gram-negative bacteria and their biofilms.

Near-Infrared Light-Activated Phototherapy by Gold Nanoclusters for Dispersing Biofilms

A bacterial biofilm is strongly associated with chronic infections and is difficult to be eradicated, posing serious threats to public health. Development of effective therapeutic strategies to prevent and control hospital-acquired infections via eradication of bacteria shielded by biofilms is challenging. Herein, we developed deoxyribonuclease (DNase)-functionalized gold nanoclusters (AuNCs) (DNase-AuNCs), which are capable of killing Gram-positive and Gram-negative bacteria, especially dispersing the surrounding biofilms. The DNase can break down the extracellular polymeric substance matrix to expose the defenseless bacteria to photothermal therapy (PTT) and photodynamic therapy (PDT) by DNase-AuNCs under 808 nm laser irradiation. The combination of enzymolysis, PDT, and PTT can effectively remove biofilms with a dispersion rate of up to 80% and kill ∼90% of the shielded bacteria. DNase-AuNCs exhibit an outstanding therapeutic effect in treating bacterial biofilm-coated orthodontic devices (Invisalign aligners), suggesting their potential applications in medical devices.

A Supramolecular-Based Dual-Wavelength Phototherapeutic Agent with Broad-Spectrum Antimicrobial Activity Against Drug-Resistant Bacteria

With the ever-increasing threat posed by the multi-drug resistance of bacteria, the development of non-antibiotic agents for the broad-spectrum eradication of clinically prevalent superbugs remains a global challenge. Here, we demonstrate the simple supramolecular self-assembly of structurally defined graphene nanoribbons (GNRs) with a cationic porphyrin (Pp4N) to afford unique one-dimensional wire-like GNR superstructures coated with Pp4N nanoparticles. This Pp4N/GNR nanocomposite displays excellent dual-modal properties with significant reactive-oxygen-species (ROS) production (in photodynamic therapy) and temperature elevation (in photothermal therapy) upon light irradiation at 660 and 808 nm, respectively. This combined approach proved synergistic, providing an impressive antimicrobial effect that led to the complete annihilation of a wide spectrum of Gram-positive, Gram-negative, and drug-resistant bacteria both in vitro and in vivo. The study also unveils the promise of GNRs as a new platform to develop dual-modal antimicrobial agents that are able to overcome antibiotic resistance.

Poly(3,4-ethylenedioxythiophene) Bearing Pyridylboronic Acid Group for Specific Recognition of Sialic Acid

Conducting polymers tethered with molecular recognition elements are good candidates for biosensing applications such as detecting a target molecule with selectivity. We develop a new monomer, namely, 3,4-ethylenedioxythiophene bearing a pyridylboronic acid moiety (EDOT-PyBA), for label-free detection of sialic acid as a cancer biomarker. PyBA, which is known to show specific binding to sialic acid in acid conditions is used as a synthetic ligand instead of lectins. PyBA confirms the enhanced binding affinity for sialic acid at pH 5.0-6.0 compared with traditional phenylboronic acid. Poly(EDOT-PyBA) is electrodeposited on a planar glassy carbon electrode and the obtained film is successfully characterized by X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, water contact angle measurements, and electrochemical impedance spectroscopy. The specific interaction of PyBA with sialic acid at the solution/electrode interface is detected by differential pulse voltammetry in a dynamic range 0.1-3.0 mM with a detection limit of 0.1 mM for a detection time of 3 min. The sensitivity covers the total level of free sialic acid in human serum and the assay time is the shorter than that of other methods. The poly(EDOT-PyBA) electrode successfully detects spiked sialic acid in human serum samples. Owing to its processability, mass productivity, and robustness, polythiophene conjugated with "boronolectin" is a candidate material for developing point-of-care and wearable biosensors.

Boronic Acid Modified Polymer Nanoparticles for Enhanced Bacterial Deactivation

A new method has been developed to enhance the antibacterial efficiency of traditional antibiotics. Chloramphenicol-imprinted polymer particles were decorated with boronic acid to improve their binding to both Gram-negative and -positive bacteria. The polymer particles have a high antibiotic loading and provide a slow release of the antibiotic payload to deactivate the target bacteria. The boronic acid modified polymer particles not only contribute to enhanced antibacterial efficiency, but also have the potential to act as scavengers to remove unused antibiotic from the environment.

Design of an Amphiphilic Perylene Diimide for Optical Recognition of Anticancer Drug through a Chirality-Induced Helical Structure

Introduction of chirality into a supramolecular self-assembly system plays an indispensable role in attaining specific molecular recognition ability. Herein, a chiral anticancer drug 5'-deoxy-5-fluorouridine (5'DFU) was explored for inducing the self-assembly of a cationic perylene diimide derivative containing boronic acid groups (PDI-PBA) into a highly ordered right-handed helical structure. As a result, PDI-PBA exhibited a molecular recognition ability towards 5'DFU among other cis-diols and anticancer drugs. With the help of a dynamic covalent bond and favorable hydrogen-bonding interactions, chirality transfer from chiral 5'DFU to achiral PDI-PBA breaks down the strong π-π stacking of PDI-PBA and makes it reorganize into highly ordered helical supramolecular structures. This work provides an insight into chiral anticancer drug tuning interactions of π-chromophores and the inducement of hierarchical self-assembly to achieve specific molecular recognition.

Rejuvenated Photodynamic Therapy for Bacterial Infections

The emergence of multidrug resistant bacterial strains has hastened the exploration of advanced microbicides and antibacterial techniques. Photodynamic antibacterial therapy (PDAT), an old-fashioned technique, has been rejuvenated to combat "superbugs" and biofilm-associated infections owing to its excellent characteristics of noninvasiveness and broad antibacterial spectrum. More importantly, bacteria are less likely to produce drug resistance to PDAT because it does not require specific targeting interaction between photosensitizers (PSs) and bacteria. This review mainly focuses on recent developments and future prospects of PDAT. The mechanisms of PDAT against bacteria and biofilms are briefly introduced. In addition to classical macrocyclic PSs, several innovative PSs, including non-self-quenching PSs, conjugated polymer-based PSs, and nano-PSs, are summarized in detail. Numerous multifunctional PDAT systems such as in situ light-activated PDAT, stimuli-responsive PDAT, oxygen self-enriching enhanced PDAT, and PDAT-based multimodal therapy are highlighted to overcome the inherent defects of PDAT in vivo (e.g., limited penetration depth of light and hypoxic environment of infectious sites).

Effects of Programmed Local Delivery from a Micro/Nano-Hierarchical Surface on Titanium Implant on Infection Clearance and Osteogenic Induction in an Infected Bone Defect

The two major causes for implant failure are postoperative infection and poor osteogenesis. Initial period of osteointegration is regulated by immunocytes and osteogenic-related cells resulting in inflammatory response and tissue healing. The healing phase can be influenced by various environmental factors and biological cascade effect. To synthetically orchestrate bone-promoting factors on biomaterial surface, built is a dual delivery system coated on a titanium surface (abbreviated as AH-Sr-AgNPs). The results show that this programmed delivery system can release Ag⁺ and Sr²⁺ in a temporal-spatial manner to clear pathogens and activate preosteoblast differentiation partially through manipulating the polarization of macrophages. Both in vitro and in vivo assays show that AH-Sr-AgNPs-modified surface renders a microenvironment adverse for bacterial survival and favorable for macrophage polarization (M2), which further promotes the differentiation of preosteoblasts. Infected New Zealand rabbit femoral metaphysis defect model is used to confirm the osteogenic property of AH-Sr-AgNPs implants through micro-CT, histological, and histomorphometric analyses. These findings demonstrate that the programmed surface with dual delivery of Sr²⁺ and Ag⁺ has the potential of achieving an enhanced osteogenic outcome through favorable immunoregulation.