Friends against the Foe: Synergistic Photothermal and Photodynamic Therapy against Bacterial Infections

Research progress on MXenes in polysaccharide-based hemostasis and wound healing: A review

Traumatic events occur frequently in daily life, and hemostasis and infection prevention represent key challenges in trauma care. Polysaccharide-based materials (chitosan, cellulose, etc.) are widely used as hemostasis materials due to their excellent designability and biocompatibility. However, their insufficient antibacterial activity and limited hemostatic capabilities diminish their effectiveness in wound care. As emerging two-dimensional nanomaterials, MXene offers promising solutions to these limitations. With superior hydrophilicity, antibacterial properties and biocompatibility, MXene enhances the performance of polysaccharide-based hemostasis materials. This review summarizes the characteristics and synthesis methods of MXenes and outlines recent advances in MXene/polysaccharide composites for promoting wound healing by controlling bleeding and preventing infection. Additionally, we discuss the preparation methods, the mechanisms of action, and challenges in practical applications of MXene/polysaccharide composites, and propose future research directions. By integrating the advantages of MXenes and polysaccharides, we hope to provide a more effective solution for the research of polysaccharide-based hemostatic materials.

Cationic porphyrin-based covalent organic frameworks for enhanced phototherapy and targeted chemotherapy of bacterial infections

Bacterial infections significantly impede wound healing and threaten global public health. Porphyrin covalent organic frameworks (COFs) have shown promise as phototherapy antibacterial materials. However, the inherent π-π stacking interactions between the monomers also lead to aggregation and quenching of photosensitizers, thereby reducing the production of singlet oxygen (1O2) and compromising their antibacterial efficacy. Herein, we designed and prepared a novel cationic porphyrin-based COFs nanoplatform (TAPP-VIO), utilizing photosensitive TAPP and cationic VIO as structural units. This multifunctional nanoplatform is specifically tailored for targeted phototherapy and chemotherapy against bacterial infections. Upon irradiation, TAPP unit in TAPP-VIO generates heat and 1O2, which effectively disrupt bacterial structure and cause cell death. The incorporation of VIO unit introduces electrostatic repulsion between layers, mitigating π-π stacking effects and enhancing 1O2 production. Additionally, the positive charge imparted by the VIO unit enables TAPP-VIO to bind efficiently to negatively charged bacterial surfaces, immobilizing the bacteria and reducing their motility, thereby improving the overall efficacy of phototherapy. Under identical experimental conditions and concentrations, TAPP-VIO exhibits a 1O2 generation capacity that is 179 % higher than that of nonionic porphyrin COF. Moreover, the temperature increase induced by TAPP-VIO is 85 % of that observed with nonionic porphyrin COF (TAPP-MMA-Da), which is conducive to enhancing the phototherapeutic effects while minimizing heat-induced damage to healthy tissues. In summary, our study presents a straightforward approach to developing non-antibiotic antibacterial nanoagents, and the as-prepared TAPP-VIO is a promising candidate drug suitable for clinical trials in the future.

Hybrid Nanoplatforms Based on Photosensitizers and Metal/Covalent Organic Frameworks for Improved Cancer Synergistic Treatment Nano-Delivery Systems

Researchers have extensively investigated photosensitizer (PS) derivatives for various applications due to their superior photophysical and electrochemical properties. However, inherent problems, such as instability and self-quenching under physiological conditions, limit their biological applications. Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) represent two relatively new material types. These materials have high surface areas and permanent porosity, and they show a tremendous deal of potential for applications like these. This review summarizes key synthesis processes and highlights recent advancements in integrating PS-based COF and MOF nanocarriers for biomedical applications while addressing potential obstacles and prospects.

Blazing Carbon Dots: Unfolding its Luminescence Mechanism to Photoinduced Biomedical Applications

Carbon dots (CDs) are carbon-based nanomaterials that have garnered immense attention owing to their exceptional photophysical and optoelectronic properties. They have been employed extensively for biomedical imaging and phototherapy due to their superb water dispersibility, low toxicity, outstanding biocompatibility, and exceptional tissue permeability. This review summarizes the structural classification of CDs, the classification of CDs according to precursor sources, and the luminescence mechanism of CDs. The modification in CDs via various doping routes is comprehensively reviewed, and the effect of such alterations on their photophysical properties, such as absorbance, photoluminescence (PL), and reactive oxygen species generation ability, is also highlighted. This review strives to summarize the role of CDs in cellular imaging and fluorescence lifetime imaging for cellular metabolism. Subsequently, recent advancements and the future potential of CDs as nanotheranostic agents have been discussed. Herein, we have discussed the role of CDs in photothermal, photodynamic, and synergistic therapy of anticancer, antiviral, and antibacterial applications. The overall summary of the review highlights the prospects of CD-based research in bioimaging and biomedicine.

Polydopamine-assisted decoration of silver nanoparticles on gold nanorods for photothermal and chemical antimicrobial applications

AuNRs@PDA@AgNPs were prepared by assembling AgNPs on AuNRs with the assistance of PDA, realizing synergistic photothermal and chemical sterilization.

Recent Advances in Porphyrin-Based Covalent Organic Frameworks for Synergistic Photodynamic and Photothermal Therapy

Porphyrin's excellent biocompatibility and modifiability make it a widely studied photoactive material. However, its large π-bond conjugated structure leads to aggregation and precipitation in physiological solutions, limiting the biomedical applications of porphyrin-based photoactive materials. It has been demonstrated through research that fabricating porphyrin molecules into nanoscale covalent organic frameworks (COFs) structures can circumvent issues such as poor dispersibility resulting from hydrophobicity, thereby significantly augmenting the photoactivity of porphyrin materials. Porphyrin-based COF materials can exert combined photodynamic and photothermal effects, circumventing the limitations of photodynamic therapy (PDT) due to hypoxia and issues in photothermal therapy (PTT) from heat shock proteins or the adverse impact of excessive heat on the protein activity of normal tissue. Furthermore, the porous structure of porphyrin COFs facilitates the circulation of oxygen molecules and reactive oxygen species and promotes sufficient contact with the lesion site for therapeutic functions. This review covers recent progress regarding porphyrin-based COFs in treating malignant tumors and venous thrombosis and for antibacterial and anti-inflammatory uses via combined PDT and PTT. By summarizing relevant design strategies, ranging from molecular design to functional application, this review provides a reference basis for the enhanced phototherapy application of porphyrin-based COFs as photoactive materials. This review aims to offer valuable insights for more effective biomedical applications of porphyrin-based COFs through the synthesis of existing experimental data, thereby paving the way for their future preclinical utilization.

Nanotechnology-Based Strategies for Safe and Effective Immunotherapy

Cancer immunotherapy using immune checkpoint blockades has emerged as a promising therapeutic approach. However, immunotherapy faces challenges such as low response rates in solid tumors, necessitating strategies to remodel the immune-suppressive tumor microenvironment (TME) into an immune-activated state. One of the primary approaches to achieve this transformation is through the induction of immunogenic cell death (ICD). Herein, we discussed strategies to maximize ICD induction using nanoparticles. In particular, this review highlighted various studies integrating chemotherapy, radiation therapy (RT), photodynamic therapy (PDT), and photothermal therapy (PTT) with nanoparticle-based immunotherapy. The research covered in this review aims to provide valuable insights for future studies on nanoparticle-assisted immunotherapy.

A targeting nanoplatform for chemo-photothermal synergistic therapy of small-cell lung cancer

The precise delivery of drugs to tumor sites and the thermoresistance of tumors remain major challenges in photothermal therapy (PTT). Somatostatin receptor 2 (SSTR2) is proposed as an ideal target for the precise treatment of SCLC. We developed a targeting nano-drug delivery system comprising anti-SSTR2 monoclonal antibody (MAb) surface-modified nanoparticles co-encapsulating Cypate and gambogic acid (GA). The formed SGCPNs demonstrated excellent monodispersity, physiological stability, preferable biocompatibility, and resultant efficient photothermal conversion efficacy. SGCPNs were quickly internalized by SSTR2-overexpressing SCLC cells, triggering the release of GA under acidic and near-infrared (NIR) laser irradiation environments, leading to their escape from lysosomes to the cytosol and then diffusion into the nucleus. SGCPNs can not only decrease the cell survival rate but also inhibit the activity of heat shock protein 90 (HSP90). SGCPNs can be precisely delivered to xenograft tumors of SSTR2-positive SCLC in vivo. Upon NIR laser irradiation, therapy of SGCPNs showed significant tumor regression. In conclusion, SGCPNs provide a new chemo-photothermal synergistic treatment strategy for targeting SCLC.

NIR-intervened thermally accelerated urease-propelled MOF nanosubmarine for antibiotic-free antibacterial inhibition via single-wavelength synergistic PDT/PTT

The increasing resistance of bacteria to antibiotics poses a serious threat to global human health. Herein, we have developed a thermal-accelerated biomacromolecular urease-driven MOF-based nanomotor (ZIF-8@PDA@ICG@Ur) mediated via NIR-intervened antimicrobial therapy. In this system, we have attempted for the first time to introduce an easy-to-operate light combination therapy strategy (only one light source is required) into an enzyme-driven MOF motor system to achieve antibiotic-free antibacterial therapy. The purpose of this research is to utilize the increased thermal energy from the photothermal effect to enhance the activity of urease, boost the driving force, which further increases the contact efficiency of the nanocarrier with the bacteria to enhance the bacterial killing power. In 50 mM urea solution, the rate of nanomotor movement was increased by about 1.24 times under NIR light irradiation compared to that without light. In addition, the synergistic effect of enhanced autonomous movement, NIR-controlled on-demand phototherapy and zinc ions release achieved 99.99 % antibacterial activity without antibiotics. The developed NIR-intervened design in this manuscript endows urease-based nanomotors with attractive propulsion feature and contributes to a novel strategy for against diseases caused by bacterial infections.

Near infrared photothermal inactivation of Candida albicans assisted by plasmonic nanorods

The use of photothermal processes has been proven effective in the control of microbial infections. Simultaneously, the localized surface plasmon resonance phenomena in metallic nanoparticles have been explored as an alternative strategy to achieve highly efficient localized heating. In this work, we propose the use of selected nanoheaters to improve the efficiency of fungal photothermal inactivation of Candida albicans through size optimization of plasmonic gold nanorods. Here, the optical heating of polyethylene glycol coated gold nanorods of varying sizes is evaluated, both theoretically and experimentally. A size-dependent computational approach was applied to identify metallic nanorods with maximized thermal performance at 800 nm, followed by the experimental comparison of optimal and suboptimal nanoheaters. Comparison among samples show temperatures of up to 53.0 °C for 41×10 nm gold nanorods against 32.3 °C for 90×25 nm, a percentage increase of ∼63% in photothermal inactivation assessments. Our findings reveal that gold nanorods of 41×10 nm exhibit superior efficiency in near-infrared (800 nm) photothermal inactivation of fungi, owing to their higher light-thermal conversion efficiency. The identification of high performance metallic nanoheaters may lead to the reduction of the nanoparticle dose used in plasmonic-based procedures and decrease the laser exposure time needed to induce cell death. Moreover, our results provide insights to better exploit plasmonic nanoparticles on photothermal inactivation protocols.

A comprehensive guide on screening and selection of a suitable AMP against biofilm-forming bacteria

Lately, antimicrobial resistance (AMR) is increasing at an exponential rate making it important to search alternatives to antibiotics in order to combat multi-drug resistant (MDR) bacterial infections. Out of the several antibacterial and antibiofilm strategies being tested, antimicrobial peptides (AMPs) have shown to give better hopes in terms of a long-lasting solution to the problem. To select a desired AMP, it is important to make right use of available tools and databases that aid in identification, classification, and analysis of the physiochemical properties of AMPs. To identify the targets of these AMPs, it becomes crucial to understand their mode-of-action. AMPs can also be used in combination with other antibacterial and antibiofilm agents so as to achieve enhanced efficacy against bacteria and their biofilms. Due to concerns regarding toxicity, stability, and bioavailability, strategizing drug formulation at an early-stage becomes crucial. Although there are few concerns regarding development of bacterial resistance to AMPs, the evolution of resistance to AMPs occurs extremely slowly. This comprehensive review gives a deep insight into the selection of the right AMP, deciding the right target and combination strategy along with the type of formulation needed, and the possible resistance that bacteria can develop to these AMPs.

Material-based treatment strategies against intraosseous implant biofilm infection

Implant-associated infections present a significant clinical obstacle for orthopedic practitioners, with bacterial biofilm formation serving as a pivotal factor in the initiation, progression, and management of such infections. Conventional approaches have proven inadequate in fully eradicating biofilm-related infections. Consequently, novel material-based therapeutic strategies have been developed, encompassing the utilization of antimicrobial agents, delivery vehicles, and synergistic antibacterial systems. In this review, we provide a succinct overview of recent advancements in anti-biofilm strategies, with the aim of offering insights that may aid in the treatment of intraosseous implant infections.

Near-Infrared Light-Mediated Antibacterial Photodynamic Therapy Based on Erythrosine-Functionalized Mesoporous Silica-Coated Upconversion Nanoplatform

Infectious diseases caused by bacteria pose a serious threat to public health, and more worryingly, the unregulated application of antibiotics accelerates the emergence of bacterial resistance, presenting a major challenge to the effective treatment of infectious diseases caused by bacteria. Therefore, there is an urgent necessity to develop efficient and safe antimicrobial systems. Photodynamic therapy (PDT) is an attractive therapeutic approach that does not induce bacterial resistance. However, the clinical application of PDT has been limited by several factors, including the lower tissue penetration depth of photoactivation under visible light irradiation and the uncertain biosafety of photosensitizers (PS). This work presents an near infrared (NIR)-triggered core-shell upconversion nanoparticle-based PDT system composed of mesoporous silica-coated lanthanide-doped upconversion nanoparticles loaded with the photosensitizer erythrosine (UCSE). Upon NIR-triggering, erythrosine generates highly efficient reactive oxygen species that disrupt the cell membranes of Staphylococcus aureus and Escherichia coli, exhibiting a potent photodynamic antimicrobial effect. It is worth noting that the UCSE also exhibits excellent biosafety. In conclusion, we present an efficient NIR-triggered nanoantimicrobial system with excellent antimicrobial capacity and biosafety, which is a new therapeutic strategy for the control of bacterial infectious diseases.

Preparation of MPN@Zein-PpIX Membrane and Its Antibacterial Properties

For antibacterial purposes, a photothermal and photodynamic antibacterial membrane was prepared through electrospinning. We used zein as the substrate and introduced Protoporphyrin IX (PpIX) into the protein structure. Then, we used electrospinning technology to weave the modified zein into a fiber structure. We finally introduced a metallic polyphenol network (MPN) coating on the fiber surface to form the final membrane: MPN@Zein-PpIX. Then, we investigated the photothermal and photodynamic properties of the membrane and assessed its antibacterial activity with in vitro agar plate counting methods. The MPN@Zein-PpIX membrane exhibited good singlet oxygen generation and excellent photothermal conversion. Additionally, it showed good antibacterial capacity in vitro, owing to the combination of photothermal and photodynamic properties. Our research provides a simple approach to prepare a multifunctional membrane with excellent antibacterial ability. We used the electrospinning technique to anchor PpIX onto zein to produce a fiber membrane (Zein-PpIX) that can be adhered in situ to improve the biocompatibility of PpIX, and the MPN makes the membrane surface more hydrophilic and more accessible to adhere to biological tissues. The MPN@Zein-PpIX membrane provided new ideas for combining PDT and PTT, and it had great potential for use in the antibacterial application field.

Photodynamic therapy alone or in combination to counteract bacterial infections

INTRODUCTION

Antibacterial photodynamic therapy presents a promising alternative to antibiotics, with potential against multidrug-resistant bacteria, offering broad-spectrum action, reduced resistance risk, and improved tissue selectivity.

AREAS COVERED

This manuscript reviews patent literature in the field of antibacterial photodynamic therapy through the period of 2019-2023. All data are from the US and European patent databases and SciFinder.

EXPERT OPINION

Antibacterial photodynamic therapy (PDT) is an appealing approach for treating bacterial infections, especially biofilm-related ones, by releasing reactive oxygen species (ROS) upon light activation. Its success is driven by a growing variety of photosensitizers (PSs) with tailored properties, like water solubility, controllable surface charge, and ROS generation efficiency. Among them, Aggregation Induced Emission (AIE)-type PSs are promising, demonstrating enhanced efficacy when aggregated in biological environments. However, the penetration of pristine PSs into bacterial biofilms within deep tissues or complex anatomical regions is limited, reducing their antibacterial effectiveness. To address this, nanotechnology has been integrated into antibacterial PDT to synthesize various nano-PSs. This adaptability allows seamless integration with other antimicrobial treatments, offering a comprehensive approach to combat localized infections, especially in dentistry and dermatology. By combining PSs with complementary therapies, antibacterial PDT offers a multifaceted strategy for effective microbial control and management.

Polydopamine-curcumin coating of titanium for remarkable antibacterial activity via synergistic photodynamic and photothermal properties

Combined photothermal therapy (PTT) and photodynamic therapy (PDT) has emerged as a novel and effective antibacterial strategy. In order to endow titanium (Ti) with antibacterial properties, the Ti-PDA-Cur composite was prepared using the excellent adhesion properties of polydopamine (PDA) to load curcumin (Cur) on the surface of Ti. The Ti-PDA-Cur coating can produce singlet oxygen (1O2) and heat under 405 + 808 nm light irradiation, which can effectively kill Staphylococcus aureus and Escherichia coli. Moreover, the cytotoxicity and hemolysis rate of Ti-PDA-Cur were low, indicating its good biocompatibility. Therefore, this study provided a new strategy for the development of new Ti implants.

Construction of gelatin/alginate hydrogels doped hemicyanine derivatives for photodynamic antibacterial application

Hydrogel systems based on natural polymer materials have provided alternative opportunities for preparing antimicrobial dressings. A composite antibacterial hydrogel system containing gelatin (Gel), alginate (Alg) and hemicyanine derivatives with different chain lengths (C3, C6 and C10) was constructed. The composite hydrogels have excellent swelling ability and low degradability due to the classical three-dimensional network structure. Because of the photosensitization ability of C3, C6 and C10, hydrogels containing these molecules can also effectively produce reactive oxygen species (ROS) under light. Importantly, the hydrogel containing C3 molecules that have higher spatial extension structure and shorter alkyl chain than C6 and C10 shows better photo-responsive antibacterial effect against drug-resistant Escherichia coli. The bacterial killing activity of the composite hydrogel system could be regulated by changing the alkyl chain length of the photosensitizers. This effective and photo-responsive composite hydrogel system is expected to be used for bacteria-infected wound repair and promoting wound healing.

Advances in Development of Novel Therapeutic Strategies against Multi-Drug Resistant Pseudomonas aeruginosa

Pseudomonas aeruginosa (P. aeruginosa) with multi-drug resistance (MDR) is a major cause of serious healthcare-associated infections, leading to high morbidity and mortality. This opportunistic pathogen is responsible for various infectious diseases, such as those seen in cystic fibrosis, ventilator-associated pneumonia, urinary tract infection, otitis externa, and burn and wound injuries. Due to its relatively large genome, P. aeruginosa has great diversity and can use various molecular mechanisms for antimicrobial resistance. For example, outer membrane permeability can contribute to antimicrobial resistance and is determined by lipopolysaccharide (LPS) and porin proteins. Recent findings on the regulatory interaction between peptidoglycan and LPS synthesis provide additional clues against pathogenic P. aeruginosa. This review focuses on recent advances in antimicrobial agents and inhibitors targeting LPS and porin proteins. In addition, we explore current and emerging treatment strategies for MDR P. aeruginosa, including phages, vaccines, nanoparticles, and their combinatorial therapies. Novel strategies and their corresponding therapeutic agents are urgently needed for combating MDR pathogens.

Photodynamic Suppression of Enterococcus Faecalis in Infected Root Canals with Indocyanine Green, TroloxTM and Near-Infrared Light

Recently, our group showed that additional supplementation of Trolox™ (vitamin E analogue) can significantly enhance the antimicrobial photodynamic effect of the photosensitizer Indocyanine green (ICG). Up to now, the combined effect has not yet been investigated on Enterococcus faecalis in dental root canals. In the present in vitro study, eighty human root canals were inoculated with E. faecalis and subsequently subjected to antimicrobial Photodynamic Therapy (aPDT) using ICG (250, 500, 1000 µg/mL) and near-infrared laser light (NIR, 808 nm, 100 Jcm-2). Trolox™ at concentrations of 6 mM was additionally applied. As a positive control, irrigation with 3% NaOCl was used. After aPDT, root canals were manually enlarged and the collected dentin debris was subjected to microbial culture analysis. Bacterial invasion into the dentinal tubules was verified for a distance of 300 µm. aPDT caused significant suppression of E. faecalis up to a maximum of 2.9 log counts (ICG 250 µg/mL). Additional application of TroloxTM resulted in increased antibacterial activity for aPDT with ICG 500 µg/mL. The efficiency of aPDT was comparable to NaOCl-irrigation inside the dentinal tubules. In conclusion, ICG significantly suppressed E. faecalis. Additional application of TroloxTM showed only minor enhancement. Future studies should also address the effects of TroloxTM on other photodynamic systems.

Construction of mPt/ICG-αA nanoparticles with enhanced phototherapeutic activities for multidrug-resistant bacterial eradication and wound healing

The emergence of multidrug-resistant (MDR) bacterial infections calls for novel strategies for effective bacterial inhibition and wound healing. Phototherapeutic approaches are promising in treating bacterial infection because of their high efficiency, noninvasiveness, and few side effects; however, their antibacterial effect is limited by the formation of biofilms in wounds. Herein, we report novel composite nanoparticles (mPt/ICG-αA NPs) combining mesoporous platinum (mPt) nanoparticles, indocyanine green (ICG) and α-amylase (αA) for combating MDR bacteria and treating wound infection, which integrates a triple bacterial inhibition mechanism arising from the combination of photodynamic therapy (PDT), photothermal therapy (PTT) and α-amylase enzymatic activities. The combination of mPt and ICG significantly enhances the effect of PTT and the temperature can be increased up to 80.8 °C to induce efficacious bacterial degeneration. Meanwhile, mPt/ICG-αA (mPIA) NPs with a low concentration of 25 μg mL-1 exhibited a remarkable catalase activity (CAT) and could continuously decompose endogenous H2O2 into O2 in a hypoxic microenvironment, thereby enhancing the PDT effect to achieve broad-spectrum bactericidal activity. mPIA NPs showed excellent MDR antibacterial efficiency against both Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli), and the bactericidal rate reached up to 99.0% and 97.2% with single 808 nm near-infrared light irradiation, respectively. mPIA NPs also exhibited an excellent ability to destroy biofilms and biocompatibility. Animal experiments further suggested that mPIA NPs could achieve the successful repairment of wounds infected with S. aureus in living systems, while this platform demonstrated negligible toxicity towards mice. Considering the superior performances of mPIA NPs, the synergistic αA-CAT-PDT-PTT boosted therapeutic activity presented in the current work provides a promising method to effectively fight against biofilm-related infectious diseases and wound healing.

Recent Progress of Photothermal Therapy Based on Conjugated Nanomaterials in Combating Microbial Infections

Photothermal therapy has the advantages of non-invasiveness, low toxicity, simple operation, a broad spectrum of antibacterial ability, and non-proneness to developing drug resistance, which provide it with irreplaceable superiority in fighting against microbial infection. The effect of photothermal therapy is closely related to the choice of photothermal agent. Conjugated nanomaterials are potential candidates for photothermal agents because of their easy modification, excellent photothermal conversion efficiency, good photostability, and biodegradability. In this paper, the application of photothermal agents based on conjugated nanomaterials in photothermal antimicrobial treatment is reviewed, including conjugated small molecules, conjugated oligomers, conjugated polymers, and pseudo-conjugated polymers. At the same time, the application of conjugated nanomaterials in the combination of photothermal therapy (PTT) and photodynamic therapy (PDT) is briefly introduced. Finally, the research status, limitations, and prospects of photothermal therapy using conjugated nanomaterials as photothermal agents are discussed.