A versatile bacterial membrane-binding chimeric peptide with enhanced photodynamic antimicrobial activity

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.

Advances in the targeted theragnostics of osteomyelitis caused by Staphylococcus aureus

Bone infections caused by Staphylococcus aureus may lead to an inflammatory condition called osteomyelitis, which results in progressive bone loss. Biofilm formation, intracellular survival, and the ability of S. aureus to evade the immune response result in recurrent and persistent infections that present significant challenges in treating osteomyelitis. Moreover, people with diabetes are prone to osteomyelitis due to their compromised immune system, and in life-threatening cases, this may lead to amputation of the affected limbs. In most cases, bone infections are localized; thus, early detection and targeted therapy may prove fruitful in treating S. aureus-related bone infections and preventing the spread of the infection. Specific S. aureus components or overexpressed tissue biomarkers in bone infections could be targeted to deliver active therapeutics, thereby reducing drug dosage and systemic toxicity. Compounds like peptides and antibodies can specifically bind to S. aureus or overexpressed disease markers and combining these with therapeutics or imaging agents can facilitate targeted delivery to the site of infection. The effectiveness of photodynamic therapy and hyperthermia therapy can be increased by the addition of targeting molecules to these therapies enabling site-specific therapy delivery. Strategies like host-directed therapy focus on modulating the host immune mechanisms or signaling pathways utilized by S. aureus for therapeutic efficacy. Targeted therapeutic strategies in conjunction with standard surgical care could be potential treatment strategies for S. aureus-associated osteomyelitis to overcome antibiotic resistance and disease recurrence. This review paper presents information about the targeting strategies and agents for the therapy and diagnostic imaging of S. aureus bone infections.

Toluidine blue O photosensitizer combined with caffeic acid improves antibacterial performance by increasing the permeability of cell membrane

Photodynamic therapy has always been an antibacterial tool for solving multi-drug resistant bacteria problem, but the side effects and the low efficiency due to the high aggregation and low solubility of photosensitizers limit its application. Due to the anti-inflammatory effect of caffeic acid, two novel photosensitizers (CA-1-TBO, CA-TBO) were synthesized by conjugating caffeic acid with toluidine blue O (TBO). The structures have been characterized by 1HNMR and high-resolution mass spectrometry. The UV-vis absorption, fluorescence spectra and the octanol-water partition coefficient of two photosensitizers were measured to evaluate their photophysical properties and hydrophilic/hydrophobic properties. Compared with parent TBO, the two modified photosensitizers have shown a higher quantum yield and kinetics constants of singlet oxygen, which has been supported by the simulation results of density functional theory. As drug-resistant representatives of gram-positive and gram-negative bacteria, respectively, S. aureus and P. aeruginosa have been used for in vitro antibacterial experiments. The sterilization efficiencies of the two modified photosensitizers far exceed that of parent TBO. The results of the octanol-water partition coefficient and fluorescence quantification showed that modified photosensitizers CA-1-TBO and CA-TBO could be more accumulated than parent TBO. Based on scanning electron microscopy images, protein gel electrophoresis, and the conductivity of the bacterial solution, the possible mechanism of improved antibacterial photodynamic efficiencies could be induced by membrane permeability due to the caffeic acid effect. The findings demonstrate the significant potential of natural phenolic compounds in the development of photosensitizer molecules with characteristics such as more efficient, biocompatible and less side effects.

Conjugation of antimicrobial peptides to enhance therapeutic efficacy

The growing prevalence of antimicrobial resistance (AMR) has brought with it a continual increase in the numbers of deaths from multidrug-resistant (MDR) infections. Since the current arsenal of antibiotics has become increasingly ineffective, there exists an urgent need for discovery and development of novel antimicrobials. Antimicrobial peptides (AMPs) are considered to be a promising class of molecules due to their broad-spectrum activities and low resistance rates compared with other types of antibiotics. Since AMPs also often play major roles in elevating the host immune response, the molecules may also be called "host defense peptides." Despite the great promise of AMPs, the majority remain unsuitable for clinical use due to issues of structural instability, degradation by proteases, and/or toxicity to host cells. Moreover, AMP activities in vivo can be influenced by many factors, such as interaction with blood and serum biomolecules, physiological salt concentrations or different pH values. To overcome these limitations, structural modifications can be made to the AMP. Among several modifications, physical and chemical conjugation of AMP to other biomolecules is widely considered an effective strategy. In this review, we discuss structural modification strategies related to conjugation of AMPs and their possible effects on mode of action. The conjugation of fatty acids, glycans, antibiotics, photosensitizers, polymers, nucleic acids, nanoparticles, and immobilization to biomaterials are highlighted.

Increasing the Selectivity of Light-Active Antimicrobial Agents - Or How To Get a Photosensitizer to the Desired Target

Photosensitizers combine the inherent reactivity of reactive oxygen species with the sophisticated reaction control of light. Through selective targeting, these light-active molecules have the potential to overcome certain limitations in drug discovery. Ongoing advances in the synthesis and evaluation of photosensitizer conjugates with biomolecules such as antibodies, peptides, or small-molecule drugs are leading to increasingly powerful agents for the eradication of a growing number of microbial species. This review article, therefore, summarizes challenges and opportunities in the development of selective photosensitizers and their conjugates described in recent literature. This provides adequate insight for newcomers and those interested in this field.

Exploring the mechanism of photosensitizer conjugation on membrane perturbation of antimicrobial peptide: A multiscale molecular simulation study

Antimicrobial peptides (AMPs) exert their biological functions by perturbation with cellular membrane. Conjugation of AMPs with photosensitizer (PS) is a promising strategy for enhancing the efficacy and reducing systemic toxicity of AMPs. However, it is still elusive how the conjugated PS impacts the perturbation of AMPs on cell membrane from molecular level. Here, we addressed this issue by a multiscale computational strategy on pyropheophorbide-a (PPA) conjugated K6L9 (PPA-K6L9), a PS-AMP conjugate developed by us previously. Our atomistic molecular dynamics (MD) simulations revealed that the porphyrin moiety of PPA enhanced the stability of the conjugate in a lipid bilayer membrane model. Moreover, such moiety also maintained the amphipathic structure of K6L9, which is crucial for membrane pore formation. Coarse-grained MD simulations further showed that the conjugates aggregated in membrane environment and formed more stable toroidal pores with respect to K6L9 alone, suggesting the conjugation of PPA may enhance the membrane-disruption activity of K6L9. Consistent with this, our cellular experiments confirmed that PPA-K6L9 was more toxic to 4 T1 tumor cells than K6L9. This study provides insights into the mechanism by which PS-AMP conjugates disrupt cellular membranes and could aid in the design of more potent AMP conjugates.

NIR-II xanthene dyes with structure-inherent bacterial targeting for efficient photothermal and broad-spectrum antibacterial therapy

Development of novel broad-spectrum sterilization is an efficient strategy that can overcome drug resistance and avoid antibiotics abuse toward bacterial-infected diseases. Photothermal therapy (PTT) in the second near-infrared (NIR-II) therapeutic window with an increased tissue penetration and elevated maximal permissible exposure has attracted considerable attention in antibacterial applications. However, the lack of bacterial-targeted photothermal agents limits their further development. Herein, we developed three xanthene derivatives (CNs) with intense light harvesting ability around 1180 nm. Their bulky planar conformations facilitated the formation of H-aggregates with outstanding photothermal conversion ability and good photostability in the NIR-II therapeutic bio window. By manipulating side chains of CNs, their liposomes exhibited different surface charges, ranging from negative to positive. Remarkably, the intermolecular hydrogen bonding of CN3 dimer drived the positively charged xanthene skeleton exposed to the periphery, which endowed it natural bacterial targeting potency. Therefore, CN3 possessed a good NIR-II photothermal and broad-spectrum sterilization against Gram-positive and Gram-negative bacteria. The photothermal antibacterial activities for S. aureus and E. coli were 99.4% and 99.2%, respectively, promoting significant wound healing in bacteria-infected mice with superior biocompatibility. This structure-inherent bacterial targeting strategy as a proof-of-concept shows an efficient broad-spectrum bacterial inactivation, indicating more encouraging NIR-II photothermal antibacterial therapy. STATEMENT OF SIGNIFICANCE: Photothermal therapy (PTT) in the second near-infrared region (NIR-II, 1000-1700 nm) enables the treatment of deep inflammation more satisfactory due to higher tissue penetration depth. In this work, three new NIR-II xanthene derivatives (CNs) with intense light harvesting ability around 1180 nm were developed. CNs showed typical H-aggregated performance with bulky planar conformations and outstanding photothermal conversion ability. Density functional theory calculations revealed that the intermolecular hydrogen bonding of CN3 dimer drived the exposure of positively charged xanthene skeleton to periphery of dimer. Therefore, CN3 NPs possessed natural bacterial targeting potency and excellent NIR-II photothermal and broad-spectrum sterilization, and so as to significantly promote the wound healing of Gram-positive / negative bacteria infected mice.

Bacitracin-Engineered BSA/ICG Nanocomplex with Enhanced Photothermal and Photodynamic Antibacterial Activity

To reduce the drug resistance of bacteria and enhance the antibacterial ability in bacterial infection therapy, we designed a new antibacterial nanoagent. In this system, a photosensitizer (indocyanine green, ICG) was loaded in bovine serum albumin (BSA) through hydrophobic-interaction-induced self-assembly to form stable BSA@ICG nanoparticles. Furthermore, a positively charged antibacterial peptide bacitracin (Bac) was physically immobilized onto the surface of BSA@ICG to generate a bacterial-targeted nanomedicine BSA@ICG@Bac through electrostatic interactions. Afterward, its photodynamic and photothermal activities were intensely evaluated. Moreover, its bactericidal efficiency was assessed via in vitro antibacterial assays and bacterial biofilm destruction tests. First, the obtained BSA@ICG@Bac showed both good singlet oxygen generation property and high photothermal conversion efficiency. In addition, it showed enhanced photodynamic and photothermal antibacterial capacities and biofilm-removing ability in vitro due to Bac modification. To sum up, our research provided an economic and less-time-consuming approach to preparing antibacterial nanomedicines with excellent antibacterial ability. Therefore, the prepared antibacterial nanomedicines have great potential to be utilized in clinical trials in the future.

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.

Use of Photodynamic Therapy Associated with Antimicrobial Peptides for Bacterial Control: A Systematic Review and Meta-Analysis

Considering the challenges related to antimicrobial resistance, other strategies for controlling infections have been suggested, such as antimicrobial photodynamic therapy (aPDT) and antimicrobial peptides (AMP). This study aims to perform a systematic review and meta-analysis to obtain evidence on the antimicrobial effectiveness of aPDT associated with AMP and establish in vitro knowledge on this topic for further study designs. The PubMed, Scopus, Web of Science, Science Direct, Scielo, and Cochrane Library databases were searched. Two independent and calibrated researchers (Kappa = 0.88) performed all the systematic steps according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The odds ratio (OR) was used as the effect measure. The Peto method was used to perform the meta-analysis due to the sparse data. Twenty studies were included in the present review. The result was significant (OR = 0.14/p = 0.0235/I-squared = 0%), showing better outcomes of aPDT associated with peptides than those of aPDT alone for controlling the microbial load. Only 20% of the studies included evaluated this approach in a biofilm culture. Combined treatment with aPDT and AMP highly increased the ability of microbial reduction of Gram-positive and Gram-negative bacteria. However, additional blind studies are required to evaluate the efficacy of this therapy on microbial biofilms.

A Photosensitized Singlet Oxygen (1O2) Toolbox for Bio-Organic Applications: Tailoring 1O2 Generation for DNA and Protein Labelling, Targeting and Biosensing

Singlet oxygen (1O2) is the excited state of ground, triplet state, molecular oxygen (O2). Photosensitized 1O2 has been extensively studied as one of the reactive oxygen species (ROS), responsible for damage of cellular components (protein, DNA, lipids). On the other hand, its generation has been exploited in organic synthesis, as well as in photodynamic therapy for the treatment of various forms of cancer. The aim of this review is to highlight the versatility of 1O2, discussing the main bioorganic applications reported over the past decades, which rely on its production. After a brief introduction on the photosensitized production of 1O2, we will describe the main aspects involving the biologically relevant damage that can accompany an uncontrolled, aspecific generation of this ROS. We then discuss in more detail a series of biological applications featuring 1O2 generation, including protein and DNA labelling, cross-linking and biosensing. Finally, we will highlight the methodologies available to tailor 1O2 generation, in order to accomplish the proposed bioorganic transformations while avoiding, at the same time, collateral damage related to an untamed production of this reactive species.

Self-Deliverable Peptide-Mediated and Reactive-Oxygen-Species-Amplified Therapeutic Nanoplatform for Highly Effective Bacterial Inhibition

An "antibiotic-free strategy" provides a viable option to address bacterial infections, especially for the "superbug" challenge. However, the undesirable antibacterial activity of antibiotic-free agents hinders their practical applications. In this study, we developed a combination antibacterial strategy of coupling peptide-drug therapy with chemodynamic therapy (CDT) to achieve the effective bacterial inhibition. An amphiphilic oligopeptide (LAOOH-OPA) containing a therapeutic unit of D(KLAK)2 peptide and a hydrophobic linoleic acid hydroperoxide (LAHP) was designed. The positively charged D(KLAK)2 peptide with an α-helical conformation enabled rapid binding with microbial cells via electrostatic interaction and subsequent membrane insertion to deactivate the bacterial membrane. When triggered by Fe2+, moreover, LAHP could generate singlet oxygen (1O2) to elicit lipid bilayer leakage for enhanced bacteria inhibition. In vitro assays demonstrated that the combination strategy possessed excellent antimicrobial activity not only merely toward susceptible strains (Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli) but also toward methicillin-resistant Staphylococcus aureus (MRSA). On the mouse skin abscess model induced by S. aureus, self-assembled LAOOH-OPA exhibited a more significant bacteria reduction (1.4 log10 reduction) in the bioburden compared to that of the standard vancomycin (0.9 log10 reduction) without apparent systemic side effects. This combination antibacterial strategy shows great potential for effective bacterial inhibition.

Light-Stimulated Carbon Dot Hydrogel: Targeting and Clearing Infectious Bacteria In Vivo

Infectious bacteria evolve fast into resistance to conventional antimicrobial agents, whereas treatments for drug resistance bacteria progress more slowly. Here, we report a universally applicable photoactivated antimicrobial modality through light-responsive carbon dot-embedding soft hyaluronic acid hydrogel (CDgel). Because of the innate nature of the infectious bacteria that produce hyaluronidase, applied hyaluronic acid-based CDgel breaks down via bacteria and releases carbon dots (CDs) into the infectious sites. The released CDs possess photodynamic capabilities under light irradiation, inducing ¹O₂ generation and growth inhibition of the infectious bacteria, S. aureus and E. coli (∼99% and ∼97%, respectively), in vitro. In particular, these photodynamic effects of CDs from CDgel have been shown to accelerate the healing of infected wounds in vivo, showing a higher wound regeneration rate as compared to that of untreated wounds. Our work demonstrates that the biocompatible and shape-controllable CDgel possesses therapeutic potential as a treatment modality for the light-driven control of drug-resistant bacterial infections.

Latest trends on photodynamic disinfection of Gram-negative bacteria: photosensitizer's structure and delivery systems

Antimicrobial resistance is threatening to overshadow last century's medical advances. Etiological agents of previously eradicated infectious diseases are now resurgent as multidrug-resistant strains, especially for Gram-negative strains. Finding new therapeutic solutions is a real challenge for our society. In this framework, Photodynamic Antimicrobial ChemoTherapy relies on the generation of toxic reactive oxygen species in the presence of light, oxygen, and a photosensitizer molecule. The use of reactive oxygen species is common for disinfection processes, using chemical agents, such as chlorine and hydrogen peroxide, and as they do not have a specific molecular target, it decreases the potential of tolerance to the antimicrobial treatment. However, light-driven generated reactive species result in an interesting alternative, as reactive species generation can be easily tuned with light irradiation and several PSs are known for their low environmental impact. Over the past few years, this topic has been thoroughly studied, exploring strategies based on single-molecule PSs (tetrapyrrolic compounds, dipyrrinate derivatives, metal complexes, etc.) or on conjunction with delivery systems. The present work describes some of the most relevant advances of the last 6 years, focusing on photosensitizers design, formulation, and potentiation, aiming for the disinfection of Gram-negative bacteria.

The Trp-rich Antimicrobial Amphiphiles With Intramolecular Aromatic Interactions for the Treatment of Bacterial Infection

Antibiotic resistance is emerging as a hot issue with the abuse and overuse of antibiotics, and the shortage of effective antimicrobial agents against multidrug resistant bacteria creates a huge problem to treat the threatening nosocomial skin and soft tissue infection. Antimicrobial peptides (AMPs) exhibite enormous potential as one of the most promising candidates of antibiotic to fight against pathogenic infections because of its unique membrane penetration mechanism to kill pathogens, whereas the clinical application of AMPs still faces the challenges of production cost, stability, safety, and design strategy. Herein, a series of Trp-rich peptides was designed following the principle of paired Trp plated at the ith and ith+4 position on the backbone of peptides, based on the template (VKKX)4, where X represents W, A, or L, to study the effect of intramolecular aromatic interactions on the bioactivity of AMPs. Through comparing the antimicrobial performance, hemolysis, cytotoxicity, and stability, VW5 which is equipped with the characters of direct antimicrobial efficacy (GM=1.68μM) and physical destruction of bacterial membrane (SEM and electron microscopy) stood out from the engineering peptides. VW5 also performed well in mice models, which could significantly decrease the bacterial colony (VW5 vs infection group, 12.72±2.26 vs 5.52±2.01×109CFU/abscess), the area of dermo-necrosis (VW5 vs infection group, 0.74±0.29 vs 1.86±0.98mm2) and the inflammation cytokine levels at the abscess site without causing toxicity to the skin. Overall, this study provides a strategy and template to diminish the randomness in the exploration and design of novel peptides.

Tetrahedral DNA nanostructure improves transport efficiency and anti-fungal effect of histatin 5 against Candida albicans

OBJECTIVES

Anti-microbial peptides (AMPs) have been comprehensively investigated as a novel alternative to traditional antibiotics against microorganisms. Meanwhile, Tetrahedral DNA nanostructures (TDNs) have gained attention in the field of biomedicine for their premium biological effects and transportation efficiency as delivery vehicles. Hence, in this study, TDN/Histatin 5 (His-5) was synthesized and the transport efficiency and anti-fungal effect were measured to evaluate the promotion of His-5 modified by TDNs.

MATERIALS AND METHODS

Tetrahedral DNA nanostructures/His-5 complex was prepared via electrostatic attraction and characterized by transmission electron microscopy (TEM), polyacrylamide gel electrophoresis (PAGE), dynamic light scattering (DLS) and electrophoretic light scattering (ELS). The anti-fungal effect of the TDN/His-5 complex was evaluated by determining the growth curve and colony-forming units of C. albicans. The morphological transformation of C. albicans was observed by light microscope and scanning electron microscope (SEM). Immunofluorescence was performed, and potassium efflux was detected to mechanistically demonstrate the efficacy of TDN/His-5.

RESULTS

The results showed that Histatin 5 modified by TDNs had preferable stability in serum and was effectively transported into C. albicans, leading to the increased formation of intracellular reactive oxygen species, higher potassium efflux and enhanced anti-fungal effect against C. albicans.

CONCLUSIONS

Our study showed that TDN/His-5 was synthesized successfully. And by the modification of TDNs, His-5 showed increased transport efficiency and improved anti-fungal effect.

Amplify antimicrobial photo dynamic therapy efficacy with poly-beta-amino esters (PBAEs)

Light-activated antimicrobial agents (photosensitisers) are promising alternatives to antibiotics for the treatment of skin infections and wounds through antimicrobial photo dynamic therapy (aPDT); utilisation of this technique is still restricted by general low efficacy requiring long exposure time (in the order of tens of minutes) that make the treatment very resource intensive. We report for the first time the possibility of harvesting the cell penetrating properties of poly-beta-amino esters (PBAEs) in combination with toluidine blue O (TBO) to shorten aPDT exposure time. Candidates capable of inactivation rates 30 times quicker than pure TBO were discovered and further improvements through PBAE backbone optimisation could be foreseen. Efficacy of the complexes was PBAE-dependent on a combination of TBO uptake and a newly discovered and unexpected role of PBAEs on reactive species production. Chemometric approach of partial least square regression was employed to assess the critical PBAE properties involved in this newly observed phenomenon in order to elicit a possible mechanism. The superior antimicrobial performance of this new approach benefits from the use of well established, low-cost and safe dye (TBO) coupled with inexpensive, widely tested and biodegradable polymers also known to be safe. Moreover, no adverse cytotoxic effects of the PBAEs adjuvated TBO delivery have been observed on a skin cells in vitro model demonstrating the safety profile of this new technology.

Design of Photosensitizing Agents for Targeted Antimicrobial Photodynamic Therapy

Photodynamic inactivation of microorganisms has gained substantial attention due to its unique mode of action, in which pathogens are unable to generate resistance, and due to the fact that it can be applied in a minimally invasive manner. In photodynamic therapy (PDT), a non-toxic photosensitizer (PS) is activated by a specific wavelength of light and generates highly cytotoxic reactive oxygen species (ROS) such as superoxide (O2-, type-I mechanism) or singlet oxygen (1O2*, type-II mechanism). Although it offers many advantages over conventional treatment methods, ROS-mediated microbial killing is often faced with the issues of accessibility, poor selectivity and off-target damage. Thus, several strategies have been employed to develop target-specific antimicrobial PDT (aPDT). This includes conjugation of known PS building-blocks to either non-specific cationic moieties or target-specific antibiotics and antimicrobial peptides, or combining them with targeting nanomaterials. In this review, we summarise these general strategies and related challenges, and highlight recent developments in targeted aPDT.

The Red Color of Life Transformed - Synthetic Advances and Emerging Applications of Protoporphyrin IX in Chemical Biology

Protoporphyrin IX (PPIX) is the porphyrin scaffold of heme b, a ubiquitous prosthetic group of proteins responsible for oxygen binding (hemoglobin, myoglobin), electron transfer (cytochrome c) and catalysis (cytochrome P450, catalases, peroxidases). PPIX and its metallated derivatives frequently find application as therapeutic agents, imaging tools, catalysts, sensors and in light harvesting. The vast toolkit of accessible porphyrin functionalization reactions enables easy synthetic modification of PPIX to meet the requirements for its multiple uses. In the past few years, particular interest has arisen in exploiting the interaction of PPIX and its synthetic derivatives with biomolecules such as DNA and heme-binding proteins to evolve molecular devices with new functions as well as to uncover potential therapeutic toeholds. This review strives to shine a light on the most recent developments in the synthetic chemistry of PPIX and its uses in selected fields of chemical biology.

Cell Membrane Coating Technology: A Promising Strategy for Biomedical Applications

Cell membrane coating technology is an approach to the biomimetic replication of cell membrane properties, and is an active area of ongoing research readily applicable to nanoscale biomedicine. Nanoparticles (NPs) coated with cell membranes offer an opportunity to unite natural cell membrane properties with those of the artificial inner core material. The coated NPs not only increase their biocompatibility but also achieve effective and extended circulation in vivo, allowing for the execution of targeted functions. Although cell membrane-coated NPs offer clear advantages, much work remains before they can be applied in clinical practice. In this review, we first provide a comprehensive overview of the theory of cell membrane coating technology, followed by a summary of the existing preparation and characterization techniques. Next, we focus on the functions and applications of various cell membrane types. In addition, we collate model drugs used in cell membrane coating technology, and review the patent applications related to this technology from the past 10 years. Finally, we survey future challenges and trends pertaining to this technology in an effort to provide a comprehensive overview of the future development of cell membrane coating technology.

Susceptibility of oral bacteria to antibacterial photodynamic therapy

Effective methods for managing the oral microbiome are necessary to ensure not only the oral but also the systemic health of a human body. The purpose of this study was to determine the sensitivity of four photosensitizers (PSs) to blue light in six representative oral bacterial species that cause intraoral diseases. The following six strains were investigated: Actinomyces israelii, Enterococcus faecium, Fusobacterium nucleatum, Lactobacillus gasseri, Streptococcus mutans, Veillonella parvula. PS stock solutions (1 mg/ml) were prepared by dissolving curcumin and protoporphyrin-IX in dimethyl sulfoxide, and resazurin and riboflavin in distilled water. The inoculation of 20 ml of a bacterial suspension cultured for 24 hours was mixed with 1,980 ml of each test solution, and then a light source was placed in front of the mixture. The irradiation wavelength was 405 nm and its applied energy was 25.3 J. The independent-samples t-test and one-way analysis of variance within groups were performed to compare the antibacterial effects in the four PSs. The antibacterial susceptibility when using different PSs and visible blue-light irradiation differed between the bacterial strains. Antibacterial photodynamic therapy that includes light exposure and PSs can be used to control the oral bacteria strains related to oral disease.

Cell membrane engineering with synthetic materials: Applications in cell spheroids, cellular glues and microtissue formation

Biologically inspired materials with tunable bio- and physicochemical properties provide an essential framework to actively control and support cellular behavior. Cell membrane remodeling approaches benefit from the advances in polymer science and bioconjugation methods, which allow for the installation of un-/natural molecules and particles on the cells' surface. Synthetically remodeled cells have superior properties and are under intense investigation in various therapeutic scenarios as cell delivery systems, bio-sensing platforms, injectable biomaterials and bioinks for 3D bioprinting applications. In this review article, recent advances in the field of cell surface remodeling via bio-chemical means and the potential biomedical applications of these emerging cell hybrids are discussed. STATEMENT OF SIGNIFICANCE: Recent advances in bioconjugation methods, controlled/living polymerizations, microfabrication techniques and 3D printing technologies have enabled researchers to probe specific cellular functions and cues for therapeutic and research purposes through the formation of cell spheroids and polymer-cell chimeras. This review article highlights recent non-genetic cell membrane engineering strategies towards the fabrication of cellular ensembles and microtissues with interest in 3D in vitro modeling, cell therapeutics and tissue engineering. From a wider perspective, these approaches may provide a roadmap for future advances in cell therapies which will expedite the clinical use of cells, thereby improving the quality and accessibility of disease treatments.