Photosensitizer-Polypeptide Conjugate for Effective Elimination of Candida albicans Biofilm

A self-assembly enzyme-like hydrogel with ROS scavenging and immunomodulatory capability for microenvironment-responsive wound healing acceleration

On-demand responsive hydrogels are a promising solution for effective wound management as they can adjust their properties in response to changes in the wound environment, allowing them to provide tailored support for the healing process. However, the conventional hydrogels may not fully meet the diverse demands of the intricate healing process. Herein, a novel glycyrrhizic acid (GA) based self-assembly hydrogel coordinated with copper and polyphenol (GCP hydrogel) was developed to exhibit triggered release behavior in response to the microenvironment. The GCP hydrogel coordinated with copper and protocatechuic acid (PA) and self-assembled with GA, also exhibits enzyme-like properties by mimicking the cascade process of superoxide dismutase (SOD) and catalase (CAT), effectively scavenging reactive oxygen species (ROS). Furthermore, the on-demand release of Cu2+ at different stages of the wound healing process can not only enhance the antibacterial ability of methicillin-resistant Staphylococcus aureus (MRSA) but also intelligently promote angiogenesis with outstanding biocompatibility. In addition, the GCP hydrogel effectively modulated the activity of macrophages in response to inflammatory stimuli, exhibiting remarkable anti-inflammatory abilities and promoting tissue regeneration. The multifunctional GCP hydrogel platform has the potential to create a dynamic microenvironment that is conducive to tissue regeneration, making it an ideal candidate for smart wound management.

Natural polymer based drug-loaded hydrogel platform for comprehensive care of acute spinal cord injury

Traumatic spinal cord injury typically occurs at significant depths and triggers rapid and severe physiological responses. It is commonly accompanied by oxidative stress disorders, lipid peroxidation, accumulation of toxic aldehydes, and edema among other symptoms. The management of this condition requires intricate surgical procedures and vigilance against postoperative complications. Slow wound healing is a major clinical challenge. In this study, we developed an injectable hydrogel-based smart drug delivery platform (OPDL gel) for the treatment of cord injuries and integrated postoperative wound care. The hydrogel encapsulates the glucocorticoid dexamethasone (Dex) through a borate ester bond and can respond to degradation caused by reactive oxygen species (ROS) and pH changes in the microenvironment of spinal cord injuries. The OPDL gel was injected into the lesion with a degradation period of 60 h, enabling a controlled and intelligent release of Dex. Additionally, poly-ε-lysine macromolecules within the gel can absorb toxic aldehydes present in the microenvironment via Schiff base reactions, thereby mitigating secondary progression of spinal cord injury. When locally applied to spinal cord injuries, the gel demonstrated good biocompatibility and had a protective effect on damaged neural structures. In addition, OPDL gel also exhibited excellent bactericidal properties, achieving a 100 % kill rate against microorganisms within 80 min and providing wound healing care comparable to a commercial product, Tegaderm™. Therefore, this multifunctional hydrogel drug-loading platform represents a novel approach for integrated treatment strategies in the clinical setting to address spinal cord injuries.

Enhancing Root Canal Therapy with NIR-II Semiconducting Polymer AIEgen and Low-Concentration Sodium Hypochlorite Synergy

Despite significant efforts to eliminate bacterial biofilm within root canals, achieving effective disinfection remains challenging due to the complex anatomy and limitations of disinfectants. In this study, a second near-infrared (NIR-II) semiconducting polymer with aggregation-induced emission (AIE) properties, named PIDT-TBT, is deliberately designed and synthesized. This proposes an AIE luminogen-based sterilization strategy in synergy with a low concentration of sodium hypochlorite (NaClO). Water-dispersible PIDT-TBT nanoparticles (NPs) are prepared, demonstrating good biocompatibility, as well as photothermal and photodynamic properties. Subsequent antibacterial tests show that PIDT-TBT NPs exhibit excellent bactericidal effects against three bacterial strains: Staphylococcus aureus, Streptococcus mutans, and Enterococcus faecalis, upon 808 nm laser irradiation. In synergy with a low concentration of NaClO (0.5%) solution, PIDT-TBT NPs significantly improves the outcome of root canal treatment under 808 nm laser irradiation in a human extracted tooth root canal infection model. Additionally, it is found that PIDT-TBT NPs combine with a low concentration of NaClO solution could safely dissolve dentin debris and further increase the efficiency of root canal preparation by altering the elemental composition of the inner root canal wall.

Oxygen Self-Supplied Nanoplatform for Enhanced Photodynamic Therapy against Enterococcus Faecalis within Root Canals

The successful treatment of persistent and recurrent endodontic infections hinges upon the eradication of residual microorganisms within the root canal system, which urgently needs novel drugs to deliver potent yet gentle antimicrobial effects. Antibacterial photodynamic therapy (aPDT) is a promising tool for root canal infection management. Nevertheless, the hypoxic microenvironment within the root canal system significantly limits the efficacy of this treatment. Herein, a nanohybrid drug, Ce6/CaO2/ZIF-8@polyethylenimine (PEI), is developed using a bottom-up strategy to self-supply oxygen for enhanced aPDT. PEI provides a positively charged surface, which enables precise targeting of bacteria. CaO2 reacts with H2O to generate O2, which alleviates the hypoxia in the root canal and serves as a substrate for Ce6 under 660 nm laser irradiation, leading to the successful eradication of planktonic Enterococcus faecalis (E. faecalis) and biofilm in vitro and, moreover, the effective elimination of mature E. faecalis biofilm in situ within the root canal system. This smart design offers a viable alternative for mitigating hypoxia within the root canal system to overcome the restricted efficacy of photosensitizers, providing an exciting prospect for the clinical management of persistent endodontic infection.

Injectable Conductive Hydrogel with Self-Healing, Motion Monitoring, and Bacteria Theranostics for Bioelectronic Wound Dressing

Wounds at joints are difficult to treat and tend to recover more slowly due to the frequent motions. When using traditional hydrogel dressings, they are easy to crack and undergo bacterial infection, difficult to match and monitor the irregular wounds. Integrating multiple functions within a hydrogel dressing to achieve intelligent wound monitoring and healing remains a significant challenge. In this research, a multifunctional hydrogel is developed based on polysaccharide biopolymer, poly(vinyl alcohol), and hydroxylated graphene through dynamic borate ester bonding and supramolecular interaction. The prepared hydrogel not only exhibits rapid self-healing (within 60 s), injectable, conductive and motion monitoring properties, but also realizes in situ bacterial sensing and killing functions. It shows excellent bacterial sensitivity (within 15 min) and killing ability via the changes of electrical signals and photothermal therapy, avoiding the emergence of drug-resistant bacteria. In vivo experiments prove that the hydrogel can promote wound healing effectively. In addition, it displays great electromechanical performance to achieve real-time monitoring and prevent re-tearing of the wound at human joints. The injectable pH-responsive hydrogel with good biocompatibility demonstrates considerable potential as multifunctional bioelectronic dressing for the detection, treatment, management, and healing of infected joint wounds.

Borneol serves as an adjuvant agent to promote the cellular uptake of curcumin for enhancing its photodynamic fungicidal efficacy against Candida albicans

Candida albicans (C. albicans), a major opportunistic pathogenic fungus, is known to cause superficial skin infections. Unfortunately, the misuse of antibiotics has led to the emergence of drug resistance in fungi. Antimicrobial photodynamic therapy (aPDT), a non-antibiotic alternative, has shown potential in treating drug-resistant fungal infections. Curcumin is a photodynamically active phytochemical whose photodynamic fungicidal efficacy is largely dependent on its intracellular accumulation. However, curcumin faces challenges in penetrating the cytoplasm due to its poor water solubility and the fungal cell wall. Borneol, another monoterpenoid phytochemical, is known for its ability to enhance drug absorption. In this study, we showed that borneol improved the cellular uptake of curcumin, thereby enhancing its photodynamic fungicidal efficacy against C. albicans. This effect was attributed to borneol's ability to increase cell permeability. Transcriptomic analysis further confirmed that borneol disrupted the normal structure and function of the C. albicans cell wall and membrane, resulting in dysregulated mRNA expression of related genes and ultimately increased cell permeability. As a result, the excessive accumulation of curcumin in C. albicans triggered the overproduction of intracellular ROS upon exposure to blue light. These excessive intracellular ROS disrupted various cellular structures, interfered with essential cellular processes, inhibited biofilm formation and reduced virulence. Remarkably, borneol was also found to enhance curcumin uptake by C. albicans within biofilms, further enhancing the anti-biofilm efficacy of curcumin-mediated aPDT (Cur-aPDT). In conclusion, the results of this study strongly support the potential of borneol as an adjuvant agent to Cur-aPDT in treating superficial cutaneous fungal infections.

Recent Advances of Composite Nanomaterials for Antibiofilm Application

A biofilm is a microbial community formed by bacteria that adsorb on the surface of tissues or materials and is wrapped in extracellular polymeric substances (EPS) such as polysaccharides, proteins and nucleic acids. As a protective barrier, the EPS can not only prevent the penetration of antibiotics and other antibacterial agents into the biofilm, but also protect the bacteria in the biofilm from the attacks of the human immune system, making it difficult to eradicate biofilm-related infections and posing a serious threat to public health. Therefore, there is an urgent need to develop new and efficient antibiofilm drugs. Although natural enzymes (lysozyme, peroxidase, etc.) and antimicrobial peptides have excellent bactericidal activity, their low stability in the physiological environment and poor permeability in biofilms limit their application in antibiofilms. With the development of materials science, more and more nanomaterials are being designed to be utilized for antimicrobial and antibiofilm applications. Nanomaterials have great application prospects in antibiofilm because of their good biocompati-bility, unique physical and chemical properties, adjustable nanostructure, high permeability and non-proneness to induce bacterial resistance. In this review, with the application of composite nanomaterials in antibiofilms as the theme, we summarize the research progress of three types of composite nanomaterials, including organic composite materials, inorganic materials and organic-inorganic hybrid materials, used as antibiofilms with non-phototherapy and phototherapy modes of action. At the same time, the challenges and development directions of these composite nanomaterials in antibiofilm therapy are also discussed. It is expected we will provide new ideas for the design of safe and efficient antibiofilm materials.

Hydrogen peroxide enhanced photoinactivation of Candida albicans by a novel boron-dipyrromethene (BODIPY) derivative

Photodynamic inactivation (PDI) has received increasing attention as a promising approach to combat Candida albicans infections. This study aimed to evaluate the synergistic effect of a new BODIPY (4,4-difluoro-boradiazaindacene) derivative and hydrogen peroxide on C. albicans. BDP-4L in combination with H₂O₂ demonstrated enhanced photokilling efficacy. In suspended cultures of C. albicans, the maximum decrease was 6.20 log and 2.56 log for PDI using BDP-4L (2.5 μM) with or without H₂O₂, respectively. For mature C. albicans biofilms, 20 μM BDP-4L plus H₂O₂ eradicated C. albicans, causing an over 6.7 log count reduction in biofilm-associated cells, while only a reduction of ~ 1 log count was observed when H₂O₂ was omitted. Scanning electron microscopy analysis and LIVE/DEAD assays suggested that PDI using BDP-4L plus H₂O₂ induced more damage to the cell membrane. Correspondingly, amplification of nucleic acids release was observed in biofilms treated with the combined PDI. Additionally, we also discovered that the addition of hydrogen peroxide potentiated the generation of ¹O₂ in PDI using the singlet oxygen sensor green probe. Collectively, BDP-4L combined with H₂O₂ presents a promising approach in the treatment of C. albicans infections.

Oxydextran-based photodynamic antibacterial nanoplatform with broad-Spectrum antibacterial activity

The compounding of polysaccharide macromolecules and antibacterial agents always has been the preferred strategy to prepare antibacterial products, attracting increasing interest. Herein, a novel acid-responsive oxidized dextran-based nanoplatform (OTP NP) has been fabricated for photodynamic antibacterial therapy by combing photosensitizer monoaminoporphyrin (TPP-NH₂) with oxidized dextran (ODex) via the Schiff Base reaction. OTP NP of about 100 nm is composed of an inner hydrophobic core of 30 nm and peripheral polysaccharide macromolecules. The OTP NP killed 99.9 % of E. coli and S. aureus within 1.5 light cycles at a concentration of 200 μg/mL. Concurrently, OTP NP exhibited excellent cytocompatibility at a concentration of 1 mg/mL (about 5 folds bactericidal concentration). Particularly, except for the recognized antibacterial mechanism of photodynamic therapy, a novel mechanism of bacterial membrane damage was discovered: the bacterial cell membrane was peeled off and formed spherical particles that aggregated around the bacteria to accelerate bacterial apoptosis under the combined action of ROS and nanomaterials. Moreover, the slightly soluble drug levofloxacin (Lev) as a model drug was loaded into OTP NP to test its carrier function, providing a practicable strategy to design multifunctional polysaccharide-based photodynamic antibacterial materials.

N,N-dimethyl chitosan oligosaccharide (DMCOS) promotes antifungal activity by causing mitochondrial damage

By modifying chitosan oligosaccharide (COS) with the Eschweiler-Clarke reaction, the chitosan oligosaccharide derivative DMCOS was synthesized. FT-IR, 1D and 2D NMR spectra, MALDI-ToF MS, and elemental analysis were applied to analyze the structure of DMCOS, which revealed that the primary amines were converted into tertiary amines after methylation. DMCOS displayed less thermal stability than COS. In comparison to COS, it was discovered that DMCOS possessed more potent antimicrobial activity against four bacterial strains (Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa) and three yeast strains (Candida albicans, Candida tropicalis, and Candida parapsilosis). The antioxidant studies indicated that DMCOS had less antioxidant activity than COS. Consequently, ROS level elevated in C. albicans cells following treatment with DMCOS, which decreased mitochondrial membrane potential. It was recalled that DMCOS may kill C. albicans by causing mitochondrial damage. In addition, DMCOS was demonstrated to be non-cytotoxic.