Synthesis, Characterization, and Antimicrobial Efficacy of Photomicrobicidal Cellulose Paper

Rapid virus inactivation by nanoparticles-embedded photodynamic surfaces

The persistent threat of viral epidemics poses significant risks to human health, highlighting the urgent need for antiviral surfaces to mitigate viral transmission through bioaerosols and surface contamination. However, there is still a scarcity of readily accessible antiviral coatings to address this critical concern. In this study, we demonstrate that photodynamic nanoparticle-embedded surfaces can swiftly inactivate both enveloped and non-enveloped viruses. We prepared core-shell structured methylene blue (MB)-loaded SiO2 nanoparticles with a high reactive oxygen species (ROS) yield (0.47 ± 0.02). The superior ROS production was maintained after modifying these nanoparticles onto air filter fibers, likely due to the prevention of aggregation-caused quenching effects. Three viruses, including both enveloped and non-enveloped types, were rapidly inactivated within just 12 min (>6 log units) under medium light intensity (660 nm, 30 mW/cm2). Mechanistic studies revealed that envelope glycoproteins are the primary targets for this rapid inactivation. Thus, photodynamic nanoparticle-embedded surfaces offer a straightforward and adaptable strategy in the fight against viral epidemics.

InP-Based Quantum Dots as Photosensitizers in Photodynamic Antimicrobial Materials

Ligand-functionalized InP-based quantum dots (QDs) have been developed as an innovative class of nontoxic photosensitizer suitable for antimicrobial applications, aimed at reducing or preventing pathogen transmission from one host to another via high contact surfaces. A hot injection method followed by functionalization via ligand exchange with 9-anthracene carboxylic acid (ACA) yielded the desired core/shell InP/ZnSe/ZnS QDs. Transmission electron microscopy (TEM) revealed these QDs to be uniform in size (∼3.2 nm), with light absorption across the entire visible spectrum (λmax ∼550 nm). Under light excitation at 550 nm, the generation of singlet oxygen (1O2) was evidenced by its characteristic phosphorescence signal at 1278 nm, indicating successful energy transfer from the QDs to surface-anchored ACA ligands, in accordance with a type II mechanism for a photodynamically generated singlet oxygen. The InP/ZnSe/ZnS core/shell QDs were applied to cellulose via dip coating, and the resultant QDs-loaded material was assessed for antimicrobial photodynamic inactivation (aPDI) of both Gram-positive [methicillin-resistant Staphylococcus aureus (MRSA; ATCC-44), vancomycin-resistant Enterococcus faecium (VRE; ATCC-2320)] and Gram-negative [multidrug-resistant Acinetobacter baumannii (MDRAB; ATCC-1605), NDM-1 positive Klebsiella pneumoniae (KP; ATCC-2146)] bacteria under illumination (400-700 nm; 85 mW/cm2; 90 min). The highest inactivation was observed for MRSA, achieving at least 99.999% inactivation (5 log units). Antiviral photodynamic inactivation on human coronavirus 229E (HCoV-229E) and feline calicivirus (FCV) demonstrated complete viral inactivation (to the detection limit). Cytotoxicity studies showed that the QDs are nontoxic to mammalian cells in the dark. Together, these results confirm the promising potential of ligand-functionalized InP-based QDs to be employed as nontoxic photosensitizers as materials in self-sterilizing surfaces.

Antimicrobial Activity of Amino-Modified Cellulose Nanofibrils Decorated with Silver Nanoparticles

Silver nanoparticles (Ag NPs) conjugated with amino-functionalized cellulose nanofibrils (NH2-CNFs) were in situ-prepared by reducing silver ions with free amino groups from NH2-CNFs. The spectroscopy and transmission electron microscopy measurements confirmed the presence of non-agglomerated nanometer-in-size Ag NPs within micrometer-large NH2-CNFs of high (20 wt.-%) content. Although the consumption of amino groups during the formation of Ag NPs lowers the ζ-potential and surface charge of prepared inorganic-organic hybrids (from +31.3 to +19.9 mV and from 2.4 to 1.0 mmol/g at pH 7, respectively), their values are sufficiently positive to ensure electrostatic interaction with negatively charged cell walls of pathogens in acidic and slightly (up to pH ~8.5) alkaline solutions. The antimicrobial activity of hybrid microparticles against various pathogens (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans) is comparable with pristine NH2-CNFs. However, a long-timescale use of hybrids ensures the slow and controlled release of Ag+ ions to surrounding media (less than 1.0 wt.-% for one month).

Multimodal integrated and broadband light-driven antibacterial cellulose fabric based on π-π coupling enhanced intermolecular FRET

Fabrication of antimicrobial photodynamic therapy (aPDT) materials based on organic photosensitizers has garnered considerable attention within functional textiles. However, the UV- or narrow-band absorption range of the photosensitizers results in poor photon utilization of the fabrics, limiting the photodynamic efficiency and wasting solar energy. In this study, a broadband light-driven antibacterial cellulose fabric (CF-ZnPc/NAD) was developed by loading carboxyl-modified zinc(II) phthalocyanine photosensitizer (CAZnPc) and cationic 1,8-naphthalimide fluorescent molecule (NAD) on the fabric via covalent binding and electrostatic adsorption assembly, facilitating the intermolecular π-π coupling and fluorescence resonance energy transfer (FRET) process. There is a 2.54-fold increase in photo-induced ROS generation capacity of CF-ZnPc/NAD via the FRET process compared to that of CF-ZnPc, and it also exhibited a strong photothermal effect (PTT), wherein the temperature of the fabric increased from 24.5 to 53.5 °C within 80 s of illumination (λ > 400 nm, 75 mW/cm2). CF-ZnPc/NAD exhibited strong light-harvesting capacity and a combination of aPDT and PTT, achieving excellent antibacterial performance against Staphylococcus aureus (Gram-positive, S. aureus) and Escherichia coli (Gram-negative, E.coli) with 99.99 % bacterial reduction under 90 min of illumination (λ > 400 nm, 10 ± 1 mW/cm2). This study demonstrates a novel and facile strategy for successfully fabricating high-performance antibacterial cellulose fabrics with potential biomedical prospects.

Facile Synthesis of Cu-Doped TiO2 Particles for Accelerated Visible Light-Driven Antiviral and Antibacterial Inactivation

In this work, we present a facile and scalable hydrolysis-based route for the synthesis of copper-doped TiO2 particles for highly effective light-activated antiviral and antibacterial applications. The performance of the synthesized Cu-doped TiO2 particles is then evaluated using solution-phase antimicrobial photodynamic inactivation assays. We demonstrate that the Cu-doped TiO2 particles can successfully inactivate a wide range of pathogens with exposure to light for 90 min, including bacteria ranging from methicillin-resistant Staphylococcus aureus (99.9999%, ∼6 log units) to Klebsiella pneumoniae (99.93%, ∼3.3 log units), and viruses including feline calicivirus (99.94%, ∼3.4 log units) and HCoV-229E (99.996%, ∼4.6 log units), with the particles demonstrating excellent robustness toward photobleaching. Furthermore, a spray-coated polymer film, loaded with the synthesized Cu-doped TiO2 particles achieves inactivation of methicillin-resistant S. aureus up to 99.998% (∼4.8 log units). The presented results provide a clear advance forward in the use of metal-doped TiO2 for aPDI applications, including the scalable synthesis (kg/day) of well-characterized and robust particles, their facile incorporation into a nontoxic, photostable coating that may be easily and cheaply applied to a multitude of surfaces, and a broad efficacy against drug-resistant Gram-positive and Gram-negative bacteria, as well as against enveloped and nonenveloped viruses.

Easy and versatile cellulosic support inhibiting broad spectrum strains: synergy between photodynamic antimicrobial therapy and polymyxin B

Despite advances achieved in the health field over the last decade, infections caused by resistant bacterial strains are an increasingly important societal issue that needs to be addressed. New approaches have already been developed to overcome this problem. Photodynamic antimicrobial chemotherapy (PACT) could provide a promising alternative method to eradicate microbes. This approach has already inspired the development of innovative surfaces. Interesting results were achieved against Gram-positive bacteria, but it also appeared that Gram-negative strains, especially Pseudomonas aeruginosa, were less sensitive to PACT. However, materials coated with cationic porphyrins have already proven their wide-spectrum activity, but these materials were not suitable for industrial-scale production. The main aim of this work was the design of a large-scale evolutionary material based on PACT and antibiotic prophylaxis. Transparent regenerated cellulose has been simply impregnated with a usual cationic porphyrin (N-methylpyridyl) and an antimicrobial peptide (polymyxin B). In addition to its photophysical properties, this film exhibited a wide-spectrum bactericidal activity over 4 days despite daily application of fresh bacterial inoculums. The efficiency of PACT and polymyxin B combination could help to reduce the emergence of bacterial multi-resistant strains and we believe that this kind of material would provide an excellent opportunity to prevent bacterial contamination of bandages or packaging.

Cationic Porphyrins as Antimicrobial and Antiviral Agents in Photodynamic Therapy

Antimicrobial photodynamic therapy (APDT) has received a great deal of attention due to its unique ability to kill all currently known classes of microorganisms. To date, infectious diseases caused by bacteria and viruses are one of the main sources of high mortality, mass epidemics and global pandemics among humans. Every year, the emergence of three to four previously unknown species of viruses dangerous to humans is recorded, totaling more than 2/3 of all newly discovered human pathogens. The emergence of bacteria with multidrug resistance leads to the rapid obsolescence of antibiotics and the need to create new types of antibiotics. From this point of view, photodynamic inactivation of viruses and bacteria is of particular interest. This review summarizes the most relevant mechanisms of antiviral and antibacterial action of APDT, molecular targets and correlation between the structure of cationic porphyrins and their photodynamic activity.

Effect of photodynamic therapy on multidrug-resistant Acinetobacter baumannii: A scoping review

BACKGROUND

Acinetobacter baumannii is a Gram-negative, non-fermenting coccobacillus of the Moraxellaceae family. It is an opportunistic pathogen responsible for several hospital-acquired infections (HAIs) associated with skin and tissue infections at surgical sites, catheter-associated urinary tract infections, and central line catheters. Multidrug-resistant (MDR) A. baumannii has caused hospital outbreaks that are difficult to eradicate and represent one of the leading producers of HAIs. MDR-A. baumannii presents a broad range of resistance to different antimicrobials, including carbapenems. Due to the low sensitivity to conventional antibiotic therapies, it is necessary to identify other therapeutic options. Antimicrobial photodynamic therapy (aPDT) is a promising alternative and complementary approach to address the shortage of antimicrobials in MDR-A. baumannii. APDT combines a photosensitizer agent, light, and oxygen to achieve a bactericidal/bacteriostatic effect. The effect is given by producing reactive oxygen species (ROS) that produce photooxidative stress over bacterial structures, such as the envelope and the DNA.

METHODS

This study aims to systematically collect bibliographic information from databases such as PubMed, Scopus, and google scholar to analyze the relevant articles critically.

RESULTS

An increasing body of evidence demonstrates the efficacy of photodynamic inactivation in eliminating A. baumannii strains, both in vitro and in vivo.

CONCLUSIONS

The evidence supports that photodynamic inactivation is an alternative capable of eliminating strains of Acinetobacter baumannii and may considerably improve the treatment of MDR strains. Although they do exist, aPDT studies on MDR strains of A. baumannii are scarce and should increase since it is on these strains that photodynamic therapy becomes attractive.

Organic-Inorganic Hybrid Nanocomposites for Nanotheranostics: Special Focus on Preventing Emerging Variants of SARS-COV-2

The worldwide emerging cases of various respiratory viral diseases and the current escalation of novel coronavirus disease (COVID-19) make people considerably attentive to controlling these viruses through innovative methods. Most re-emerging respiratory diseases envelop RNA viruses that employ attachment between the virus and host cell to get an entry form using the host cell machinery. Emerging variants of COVD-19 also bring about a constant threat to public health as it has wide infectivity and can quickly spread to infect humans. This review focuses on insights into the current investigations to prevent the progression of incipient variants of Severe Acute Respiratory Syndrome Coronavirus (SARS-COV-2) along with similar enveloped RNA viruses that cause respiratory illness in humans and animals. Nanotheranostics is a trailblazing arena of nanomedicine that simultaneously helps prevent or treat diseases and diagnoses. Nanoparticle coating and nanofibers were extensively explored, preventing viral contaminations. Several studies have proven the virucidal activities of metal nanoparticles like copper, silver, and titanium against respiratory viral pathogens. Worldwide many researchers have shown surfaces coated with ionic nanoparticles like zinc or titanium act as potent antiviral agents against RNA viruses. Carbon nanotubes, quantum dots, silica nanoparticles (NPs), polymeric and metallic nanoparticles have also been explored in the field of nanotheranostics in viral detection. In this review, we have comprehensively discussed different types of metallic, ionic, organic nanoparticles and their hybrids showing substantial antiviral properties to stop the progression of the novel coronavirus disease focused on three key classes: prevention, diagnostics, and treatment.

Color-variable dual-dyed photodynamic antimicrobial polyethylene terephthalate (PET)/cotton blended fabrics

The urgent demand for scalable, potent, color variable, and comfortable antimicrobial textiles as personal protection equipment (PPE) to help reduce infection transmission in hospitals and healthcare facilities has significantly increased since the start of the COVID-19 pandemic. Here, we explored photodynamic antimicrobial polyethylene terephthalate/cotton (TC) blended fabrics comprised of photosensitizer-conjugated cotton fibers and polyethylene terephthalate (PET) fibers dyed with disperse dyes. A small library of TC blended fabrics was constructed wherein the PET fibers were embedded with traditional disperse dyes dominating the fabric color, thereby enabling variable color expression, while the cotton fibers were covalently coupled with the photosensitizer thionine acetate as the microbicidal agent. Physical (SEM, CLSM, TGA, XPS and mechanical strength) and colorimetric (K/S and CIELab values) characterization methods were employed to investigate the resultant fabrics, and photooxidation studies with DPBF demonstrated the ability of these materials to generate reactive oxygen species (i.e., singlet oxygen) upon visible light illumination. The best results demonstrated a photodynamic inactivation of 99.985% (~ 3.82 log unit reduction, P = 0.0021) against Gram-positive S. aureus, and detection limit inactivation (99.99%, 4 log unit reduction, P ≤ 0.0001) against Gram-negative E. coli upon illumination with visible light (60 min; ~ 300 mW/cm²; λ ≥ 420 nm). Enveloped human coronavirus 229E showed a photodynamic susceptibility of ~ 99.99% inactivation after 60 min illumination (400-700 nm, 65 ± 5 mW/cm²). The presence of the disperse dyes on the fabrics showed no significant effects on the aPDI results, and furthermore, appeared to provide the photosensitizer with some measure of protection from photobleaching, thus improving the photostability of the dual-dyed fabrics. Taken together, these results suggest the feasibility of low cost, scalable and color variable thionine-conjugated TC blended fabrics as potent self-disinfecting textiles.

Porphyrin Photosensitizers Grafted in Cellulose Supports: A Review

Cellulose is the most abundant natural biopolymer and owing to its compatibility with biological tissues, it is considered a versatile starting material for developing new and sustainable materials from renewable resources. With the advent of drug-resistance among pathogenic microorganisms, recent strategies have focused on the development of novel treatment options and alternative antimicrobial therapies, such as antimicrobial photodynamic therapy (aPDT). This approach encompasses the combination of photoactive dyes and harmless visible light, in the presence of dioxygen, to produce reactive oxygen species that can selectively kill microorganisms. Photosensitizers for aPDT can be adsorbed, entrapped, or linked to cellulose-like supports, providing an increase in the surface area, with improved mechanical strength, barrier, and antimicrobial properties, paving the way to new applications, such as wound disinfection, sterilization of medical materials and surfaces in different contexts (industrial, household and hospital), or prevention of microbial contamination in packaged food. This review will report the development of porphyrinic photosensitizers supported on cellulose/cellulose derivative materials to achieve effective photoinactivation. A brief overview of the efficiency of cellulose based photoactive dyes for cancer, using photodynamic therapy (PDT), will be also discussed. Particular attention will be devoted to the synthetic routes behind the preparation of the photosensitizer-cellulose functional materials.

Self-cleaning wearable masks for respiratory infectious pathogen inactivation by type I and type II AIE photosensitizer

Although face masks as personal protective equipment (PPE) are recommended to control respiratory diseases with the on-going COVID-19 pandemic, improper handling and disinfection increase the risk of cross-contamination and compromise the effectiveness of PPE. Here, we prepared a self-cleaning mask based on a highly efficient aggregation-induced emission photosensitizer (TTCP-PF₆) that can destroy pathogens by generating Type I and Type II reactive oxygen species (ROS). The respiratory pathogens, including influenza A virus H1N1 strain and Streptococcus pneumoniae (S. pneumoniae) can be inactivated within 10 min of ultra-low power (20 W/m²) white light or simulated sunlight irradiation. This TTCP-PF₆-based self-cleaning strategy can also be used against other airborne pathogens, providing a strategy for dealing with different microbes.

Water-soluble anionic polychloramide biocides based on maleic anhydride copolymers

Our goal was to develop film-forming polymers to extend the antimicrobial lifetimes of cleaned and disinfected surfaces. Antimicrobial polymers were prepared by first reacting poly(ethylene-alt-maleic anhydride) with isopropylamine, partially consuming the anhydride groups, followed by hydrolysis to give water-soluble, highly anionic polyamide PC3. Chlorination with NaOCl gave PC3Cl with oxidative chlorine contents up to 9 wt%. Dried, 5 µm thick, PC3Cl films, gave log 4 reductions in the concentration of Escherichia coli or Staphylococcus aureus exposed to films. A unique feature of the maleic anhydride copolymer platform was the ability to form covalent grafts to surfaces via anhydride reactions. PC3 solution was impregnated into cellulosic filter paper, heated to form ester linkages with cellulose, followed by chlorination with sodium dichloroisocyanurate dihydrate giving grafted PC3Cl. The treated paper (0.3 wt% PC3Cl) gave a log 4 reduction of E. coli concentration in 30 min.

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.

Contributions of photochemistry to bio-based antibacterial polymer materials

Surgical site infections constitute a major health concern that may be addressed by conferring antibacterial properties to surgical tools and medical devices via functional coatings. Bio-sourced polymers are particularly well-suited to prepare such coatings as they are usually safe and can exhibit intrinsic antibacterial properties or serve as hosts for bactericidal agents. The goal of this Review is to highlight the unique contribution of photochemistry as a green and mild methodology for the development of such bio-based antibacterial materials. Photo-generation and photo-activation of bactericidal materials are illustrated. Recent efforts and current challenges to optimize the sustainability of the process, improve the safety of the materials and extend these strategies to 3D biomaterials are also emphasized.

Molecular Engineering of Laser-Induced Graphene for Potential-Driven Broad-Spectrum Antimicrobial and Antiviral Applications

Worldwide, countless deaths have been caused by the coronavirus disease 2019. In addition to the virus variants, an increasing number of fatal fungal infections have been reported, which further exacerbates the scenario. Therefore, the development of porous surfaces with both antiviral and antimicrobial capacities is of urgent need. Here, a cost-effective, nontoxic, and metal-free strategy is reported for the surface engineering of laser-induced graphene (LIG). The authors covalently engineer the surface potential of the LIG from -14 to ≈+35 mV (LIG⁺ ), enabling both high-efficiency antimicrobial and antiviral performance under mild conditions. Specifically, several candidate microorganisms of different types, including Escherichia coli, Streptomyces tenebrarius, and Candida albicans, are almost completely inactivated after 10-min solar irradiation. LIG⁺ also exhibits a strong antiviral effect against human coronaviruses: 99% HCoV-OC43 and 100% HCoV-229E inactivation are achieved after 20-min treatment. Such enhancement may also be observed against other types of pathogens that are heat-sensitive and oppositely charged. Besides, the covalent modification strategy alleviates the leaching problem, and the low cytotoxicity of LIG⁺ makes it advantageous. This study highlights the synergy of surface potential and photothermal effect in the inactivation of pathogens and it provides a direction for designing porous materials for airborne disease removal and water disinfection.

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.

Toward Universal Photodynamic Coatings for Infection Control

The dual threats posed by the COVID-19 pandemic and hospital-acquired infections (HAIs) have emphasized the urgent need for self-disinfecting materials for infection control. Despite their highly potent antimicrobial activity, the adoption of photoactive materials to reduce infection transmission in hospitals and related healthcare facilities has been severely hampered by the lack of scalable and cost-effective manufacturing, in which case high-volume production methods for fabricating aPDI-based materials are needed. To address this issue here, we examined the antimicrobial efficacy of a simple bicomponent spray coating composed of the commercially-available UV-photocrosslinkable polymer N-methyl-4(4'-formyl-styryl)pyridinium methosulfate acetal poly(vinyl alcohol) (SbQ-PVA) and one of three aPDI photosensitizers (PSs): zinc-tetra(4-N-methylpyridyl)porphine (ZnTMPyP⁴⁺), methylene blue (MB), and Rose Bengal (RB). We applied these photodynamic coatings, collectively termed SbQ-PVA/PS, to a variety of commercially available materials. Scanning electron microscopy (SEM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) confirmed the successful application of the coatings, while inductively coupled plasma-optical emission spectroscopy (ICP-OES) revealed a photosensitizer loading of 0.09-0.78 nmol PS/mg material. The antimicrobial efficacy of the coated materials was evaluated against methicillin-susceptible Staphylococcus aureus ATCC-29213 and human coronavirus strain HCoV-229E. Upon illumination with visible light (60 min, 400-700 nm, 65 ± 5 mW/cm²), the coated materials inactivated S. aureus by 97-99.999% and HCoV-229E by 92-99.999%, depending on the material and PS employed. Photobleaching studies employing HCoV-229E demonstrated detection limit inactivation (99.999%) even after exposure for 4 weeks to indoor ambient room lighting. Taken together, these results demonstrate the potential for photodynamic SbQ-PVA/PS coatings to be universally applied to a wide range of materials for effectively reducing pathogen transmission.

Photodynamic Inactivation of Pseudomonas aeruginosa by PHEMA Films Loaded with Rose Bengal: Potentiation Effect of Potassium Iodide

Four formulations have been used to produce different poly(2-hydroxyethyl methacrylate) (PHEMA) thin films, containing singlet oxygen photosensitizer Rose Bengal (RB). The polymers have been characterized employing Thermogravimetric Analysis (TGA), Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) and UV-vis Absorption Spectroscopy. When irradiated with white light (400-700 nm) films generated singlet oxygen (1O2), as demonstrated by the reactivity with 1O2 trap 9,10-dimethylanthracene (DMA). Material with the highest RB loading (polymer A4, 835 nmol RB/g polymer) was able to perform up to ten cycles of DMA oxygenation reactions at high conversion rates (ca. 90%). Polymer A4 was also able to produce the complete eradication of a Pseudomonas aeruginosa planktonic suspension of 8 log10 CFU/mL, when irradiated with white light (total dose 72 J/cm2). The antimicrobial photodynamic effect was remarkably enhanced by adding potassium iodide (100 mM). In such conditions the complete bacterial reduction occurred with a total light dose of 24 J/cm2. Triiodide anion (I3-) generation was confirmed by UV-vis absorption spectroscopy. This species was detected inside the PHEMA films after irradiation and at concentrations ca. 1 M. The generation of this species and its retention in the matrix imparts long-lasting bactericidal effects to the RB@PHEMA polymeric hydrogels. The polymers here described could find potential applications in the medical context, when optimized for their use in everyday objects, helping to prevent bacterial contagion by contact with surfaces.

AIEgen-loaded nanofibrous membrane as photodynamic/photothermal antimicrobial surface for sunlight-triggered bioprotection

The outbreak of infectious diseases such as COVID-19 causes an urgent need for abundant personal protective equipment (PPE) which leads to a huge shortage of raw materials. Additionally, the inappropriate disposal and sterilization of PPE may result in a high risk of cross-contamination. Therefore, the exploration of antimicrobial materials possessing both microbe interception and self-decontamination effects to develop reusable and easy-to-sterilize PPE is of great importance. Herein, an aggregation-induced emission (AIE)-active luminogen-loaded nanofibrous membrane (TTVB@NM) sharing sunlight-triggered photodynamic/photothermal anti-pathogen functions are prepared using the electrospinning technique. Thanks to its porous nanostructure, TTVB@NM shows excellent interception effects toward ultrafine particles and pathogenic aerosols. Benefiting from the superior photophysical properties of the AIE-active dopants, TTVB@NM exhibits integrated properties of wide absorption in visible light range, efficient ROS generation, and moderate photothermal conversion performance. A series of antimicrobial evaluations reveal that TTVB@NM could effectively inactivate pathogenic aerosols containing bacteria (inhibition rate: >99%), fungi (~88%), and viruses (>99%) within only 10 min sunlight irradiation. This study represents a new strategy to construct reusable and easy-to-sterilize hybrid materials for potential bioprotective applications.

Highly Efficient and Rapid Inactivation of Coronavirus on Non-Metal Hydrophobic Laser-Induced Graphene in Mild Conditions

The prevalence of COVID-19 has caused global dysfunction in terms of public health, sustainability, and socio-economy. While vaccination shows potential in containing the spread, the development of surfaces that effectively reduces virus transmission and infectivity is also imperative, especially amid the early stage of the pandemic. However, most virucidal surfaces are operated under harsh conditions, making them impractical or potentially unsafe for long-term use. Here, it is reported that laser-induced graphene (LIG) without any metal additives shows marvelous antiviral capacities for coronavirus. Under low solar irradiation, the virucidal efficacy of the hydrophobic LIG (HLIG) against HCoV-OC43 and HCoV-229E can achieve 97.5% and 95%, respectively. The photothermal effect and the hydrophobicity of the HLIG synergistically contribute to the superior inactivation capacity. The stable antiviral performance of HLIG enables its multiple uses, showing advantages in energy saving and environmental protection. This work discloses a potential method for antiviral applications and has implications for the future development of antiviral materials.

Photodynamic Coatings on Polymer Microfibers for Pathogen Inactivation: Effects of Application Method and Composition

A substantial increase in the risk of hospital-acquired infections (HAIs) has greatly impacted the global healthcare industry. Harmful pathogens adhere to a variety of surfaces and infect personnel on contact, thereby promoting transmission to new hosts. This is particularly worrisome in the case of antibiotic-resistant pathogens, which constitute a growing threat to human health worldwide and require new preventative routes of disinfection. In this study, we have incorporated different loading levels of a porphyrin photosensitizer capable of generating reactive singlet oxygen in the presence of O₂ and visible light in a water-soluble, photo-cross-linkable polymer coating, which was subsequently deposited on polymer microfibers. Two different application methods are considered, and the morphological and chemical characteristics of these coated fibers are analyzed to detect the presence of the coating and photosensitizer. To discern the efficacy of the fibers against pathogenic bacteria, photodynamic inactivation has been performed on two different bacterial strains, Staphylococcus aureus and antibiotic-resistant Escherichia coli, with population reductions of >99.9999 and 99.6%, respectively, after exposure to visible light for 1 h. In response to the current COVID-19 pandemic, we also confirm that these coated fibers can inactivate a human common cold coronavirus serving as a surrogate for the SARS-CoV-2 virus.

A simple, inexpensive method for gas-phase singlet oxygen generation from sensitizer-impregnated filters: Potential application to bacteria/virus inactivation and pollutant degradation

Airborne infectious diseases such as the new Coronavirus 2019 (COVID-19) pose serious threat to human health. Indoor air pollution is a problem of global environmental concern as well. Singlet oxygen (¹O₂) is a reactive oxygen species that plays important role in bacteria/virus inactivation and pollutant degradation. In this study, we found that commercially available filters typically deployed in air purifier and air conditioning units, when impregnated with Rose Bengal (RB) as a ¹O₂ sensitizer, can be used for heterogeneous gas-phase generation of ¹O₂. It was confirmed that irradiation of the RB filter under oxygen gas stream produced ¹O₂, which was measured using furfuryl alcohol trapping method followed by HPLC analysis. It was also observed that the amount of ¹O₂ generated increases as the light intensity increased. Similarly, the sensitizer loading also positively influenced the ¹O₂ generation. The heterogeneous gas-phase generation of ¹O₂ can find potential applications in air purifier and air conditioning units for the purpose of bacteria/virus inactivation and/or pollutant degradation thereby improving indoor air quality.

Antimicrobial Nanomaterials and Coatings: Current Mechanisms and Future Perspectives to Control the Spread of Viruses Including SARS-CoV-2

The global COVID-19 pandemic has attracted considerable attention toward innovative methods and technologies for suppressing the spread of viruses. Transmission via contaminated surfaces has been recognized as an important route for spreading SARS-CoV-2. Although significant efforts have been made to develop antibacterial surface coatings, the literature remains scarce for a systematic study on broad-range antiviral coatings. Here, we aim to provide a comprehensive overview of the antiviral materials and coatings that could be implemented for suppressing the spread of SARS-CoV-2 via contaminated surfaces. We discuss the mechanism of operation and effectivity of several types of inorganic and organic materials, in the bulk and nanomaterial form, and assess the possibility of implementing these as antiviral coatings. Toxicity and environmental concerns are also discussed for the presented approaches. Finally, we present future perspectives with regards to emerging antimicrobial technologies such as omniphobic surfaces and assess their potential in suppressing surface-mediated virus transfer. Although some of these emerging technologies have not yet been tested directly as antiviral coatings, they hold great potential for designing the next generation of antiviral surfaces.

Nano Antiviral Photodynamic Therapy: a Probable Biophysicochemical Management Modality in SARS-CoV-2

INTRODUCTION

COVID-19 disease has shocked the world by its spread and contagiousness. At this time, there is no valid vaccine and no proven drug treatment for COVID-19 patients. Current treatments are focused on Oxygenation, Cytokine Storm management, anti-inflammatory effects, and antiviral therapy. Antiviral photodynamic therapy (aPDT) is based on the reaction between a photo-sensitive agent and a light source in the presence of oxygen which can produce oxidative and free radical agents to damage the virus' structures. Recent studies show that nanotechnology can improve aPDT's outcome. The aim of this study was to find out the potential therapeutic effects of Nano antiviral photodynamic therapy on COVID-19.

AREAS COVERED

This review evaluates Nano Antiviral Photodynamic Therapy: A Probable Biophysicochemical Management Modality in SARS-CoV-2. Data were extracted from published different studies published on PUBMED, SCOPUS, and Web of Science.

EXPERT OPINION

Studies indicating that aPDT and Nano-based aPDT can be useful in viral pulmonary complications like Influenza, SARS-CoV, and MERS, but there was no direct study on SARS-Cov-2. Recent studies showed that Nano-based aPDT could relate to control of the stages of viral infections. Altogether, further investigations for the application of nanomedicine in antimicrobial photodynamic inactivation are needed for COVID-19 Management.

Transmittance and Survival of SARS-CoV-2 in Global Trade: The Role of Supply Chain and Packaging

We are living in uncertain times and facing a paradigm shift in human health and sustainability. The number of SARS-CoV-2 victims is rising daily and all nations are going through dramatic effects and exploring various solutions to this imminent calamity facing the humanity. The world is confronting a public health issue that has forced it to come to a halt and evaluate the future of our modern society and our way of living. It can be stated that the sustainability of our societies inextricably depends on the performance of our global trade and supply chains. This review article is the first published assessment on the global trade and especially packaging’s role in the transmittance of SARS-CoV-2 virus. Surprisingly, based on our findings, the lack of knowledge on transmittance and survival of SARS-CoV-2 in supply chain and packaging is substantial. Although there are several existing and available technologies that can be used for the risk mitigation, our assessment shows a major and timely need for broad conceptual advancements and necessary understanding of the supply chain risks associated with the viral surface transmittances. The specificity to the current and possibly future pandemics demands an increasing amount of multidisciplinary research and involvement of public and private sectors. This proposed erudition is imminent and may be highly critical in safeguarding and the sustainability of the critical supply chains in our society now and in the future.

Color-Variable Photodynamic Antimicrobial Wool/Acrylic Blended Fabrics

Towards the goal of developing scalable, economical and effective antimicrobial textiles to reduce infection transmission, here we prepared color-variable photodynamic materials comprised of photosensitizer (PS)-loaded wool/acrylic (W/A) blends. Wool fibers in the W/A blended fabrics were loaded with the photosensitizer rose bengal (RB), and the acrylic fibers were dyed with a variety of traditional cationic dyes (cationic yellow, cationic blue and cationic red) to broaden their color range. Investigations on the colorimetric and photodynamic properties of a series of these materials were implemented through CIELab evaluation, as well as photooxidation and antibacterial studies. Generally, the photodynamic efficacy of these dual-dyed fabrics was impacted by both the choice, and how much of the traditional cationic dye was employed in the dyeing of the W/A fabrics. When compared with the PS-only singly-dyed material, RB-W/A, that showed a 99.97% (3.5 log units; p = 0.02) reduction of Staphylococcus aureus under visible light illumination (λ ≥ 420 nm, 60 min), the addition of cationic dyes led to a slight decrease in the photoinactivation ability of the dual-dyed fabrics, but was still able to achieve a 99.3% inactivation of S. aureus. Overall, our findings demonstrate the feasibility and potential applications of low cost and color variable RB-loaded W/A blended fabrics as effective self-disinfecting textiles against pathogen transmission.

Aza-BODIPY Probe-Decorated Mesoporous Black TiO2 Nanoplatform for the Highly Efficient Synergistic Phototherapy

As an important noninvasive tumor treatment method, phototherapy has drawn extensive research interest. However, the requirements of separate excitation wavelengths, high degree of electron-hole recombination, and low reactive oxygen species (ROS) production capability are still the major barriers. This work reports the construction of a novel nanoplatform: design and synthesis of an aza-BODIPY (AB) probe-decorated mesoporous black titanium dioxide (TiO₂) (MT) nanoparticles (NPs) for enhanced photodynamic therapy and photothermal therapy under single-wavelength near-infrared (NIR) laser irradiation for the first time. AB probe-decorated MT NPs (abbreviated as MTAB) were synthesized through the Al reduction of mesoporous anatase TiO₂ NPs and subsequent adsorption of the AB probe. The mesoporous structure of MT ensured AB loading capacity and avoided the complicated modification and synthesis processes. Heterogeneous MTAB, which possessed staggered energy levels, were assessed for their capability for effective separation of photogenerated electrons and holes for the first time. Upon NIR laser light irradiation, MTAB exhibited sufficient ROS generation, resulting in distinct tumor cell killing and tumor tissue elimination. This unique heterogeneous nanoplatform with staggered energy levels provides a new strategy to enhance ROS generation and improve the therapeutic efficacy.

Balancing the decomposable behavior and wet tensile mechanical property of cellulose-based wet wipe substrates by the aqueous adhesive

With the current global outbreak of novel coronaviruses, the fabrication of decomposable wet wipe with sufficient wet strength to meet daily use is promising but still challenging, especially when renewable cellulose was employed. In this work, a decomposable cellulose-based wet wipe substrate is demonstrated by introducing a synthetic N-vinyl pyrrolidone-glycidyl methacrylate (NVP-GMA) adhesive on the cellulose surface. Experimental results reveal that the NVP-GMA adhesive not only significantly facilitates the chemical bonding between cellulose fibers in the wet state, but also increase the surface wettability and water retention. The as-fabricated cellulose-based wet wipe substrate displays a superb water retention capacity of 1.9 times, an excellent water absorption capacity (completely wetted with 0° water contact angle), and a perfect wet tensile index of 3.32 N.m.g⁻¹. It is far better than state-of-the-art wet toilet wipe on the market (non-woven). The prepared renewable and degradable cellulose-based substrate with excellent mechanical strength has potential application prospects in diverse commercially available products such as sanitary and medical wet wipes.

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A decomposable wet wipe substrate was prepared from the bio-based materials.

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Synthetic adhesive enhanced the wet strength of the cellulose sheet.

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Enhancement of cellulose-based material was achieved under aqueous conditions.

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As-prepared cellulose substrate balanced the dispersibility and wet strength.

A cost-effective combination of Rose Bengal and off-the-shelf cationic polystyrene for the photodynamic inactivation of Pseudomonas aeruginosa

Two new photoactive materials have been prepared, characterized and tested against Pseudomonas aeruginosa bacteria (planktonic suspension). The synthesis of the polymeric photosensitizers can be made at a multigram scale, in few minutes, starting from inexpensive and readily available materials, such as Rose Bengal (photosensitizer) and ion exchange resins Amberlite® IRA 900 (macroporous) or IRA 400 (gel-type) as cationic polystyrene supports. The most notable feature of these systems is their notable bactericidal activity in the dark (4-5 log₁₀ CFU/mL reduction of the population of P. aeruginosa) which becomes enhanced upon irradiation with visible light (to reach a total reduction of 8 log₁₀ CFU/mL for the macroporous polymer at a fluence of 120 J/cm² using green light of 515 nm).

Carbon quantum dots: A bright future as photosensitizers for in vitro antibacterial photodynamic inactivation

Carbon nanomaterials have increasingly gained the attention of the nano-, photo- and biomedical communities owing to their unique photophysical properties. Here, we facilely synthesized carbon quantum dots (CQDs) in a one-pot solvothermal reaction, and demonstrated their utility as photosensitizers for in vitro antibacterial photodynamic inactivation (aPDI). The bottom-up synthesis employed inexpensive and sustainable starting materials (citric acid), used ethanol as an environmentally-friendly solvent, was relatively energy efficient, produced minimal waste, and purification was accomplished simply by filtration. The CQDs were characterized by both physical (TEM, X-ray diffraction) and spectroscopic (UV-visible, fluorescence, and ATR-FTIR) methods, which together confirmed their nanoscale dimensions and photophysical properties. aPDI studies demonstrated detection limit inactivation (99.9999 + %) of Gram-negative Escherichia coli 8099 and Gram-positive Staphylococcus aureus ATCC-6538 upon visible light illumination (λ ≥ 420 nm, 65 ± 5 mW/cm2; 60 min). Post-illumination SEM images of the bacteria incubated with the CQDs showed perforated and fragmented cell membranes consistent with damage from reactive oxygen species (ROS), and mechanistic studies revealed that the bacteria were inactivated by singlet oxygen, with no discernable roles for other ROS (e.g., superoxide or hydroxyl radicals). These findings demonstrated that CQDs can be facilely prepared, operate via a Type II mechanism, and are effective photosensitizers for in vitro aPDI.

Conjugating biomaterials with photosensitizers: advances and perspectives for photodynamic antimicrobial chemotherapy

Antimicrobial resistance is threatening to overshadow last century's medical advances. Previously eradicated infectious diseases are now resurgent as multi-drug resistant strains, leading to expensive, toxic and, in some cases, ineffective antimicrobial treatments. Given this outlook, researchers are willing to investigate novel antimicrobial treatments that may be able to deal with antimicrobial resistance, namely photodynamic therapy (PDT). PDT relies on the generation of toxic reactive oxygen species (ROS) in the presence of light and a photosensitizer (PS) molecule. PDT has been known for almost a century, but most of its applications have been directed towards the treatment of cancer and topical diseases. Unlike classical antimicrobial chemotherapy treatments, photodynamic antimicrobial chemotherapy (PACT) has a non-target specific mechanism of action, based on the generation of ROS, working against cellular membranes, walls, proteins, lipids and nucleic acids. This non-specific mechanism diminishes the chances of bacteria developing resistance. However, PSs usually are large molecules, prone to aggregation, diminishing their efficiency. This review will report the development of materials obtained from natural sources, as delivery systems for photosensitizing molecules against microorganisms. The present work emphasizes on the biological results rather than on the synthesis routes to prepare the conjugates. Also, it discusses the current state of the art, providing our perspective on the field.

Colorimetric Band-aids for Point-of-Care Sensing and Treating Bacterial Infection

Sensing bacterial infections and monitoring drug resistance are very important for the selection of treatment options. However, the common methods of sensing resistance are limited by time-consuming, the requirement for professional personnel, and expensive instruments. Moreover, the abuse of antibiotics causes the accelerated process of bacterial resistance. Herein, we construct a portable paper-based band-aid (PBA) which implements a selective antibacterial strategy after sensing of drug resistance. The colors of PBA indicate bacterial infection (yellow) and drug resistance (red), just like a bacterial resistance colorimetric card. On the basis of color, antibiotic-based chemotherapy and Zr-MOF PCN-224-based photodynamic therapy (PDT) are used on site to treat sensitive and resistant strains, respectively. Eventually, it takes 4 h to sense, and the limit of detection is 10⁴ CFU/mL for drug-resistant E. coli. Compared with traditional PDT-based antibacterial strategies, our design can alleviate off-target side effects, maximize therapeutic efficacy, and track the drug resistance in real time with the naked eye. This work develops a new way for the rational use of antibiotics. Given the low cost and easy operation of this point-of-care device, it can be developed for practical applications.

Towards microbe-targeted photosensitizers: Synthesis, characterization and in vitro photodynamic inactivation of the tuberculosis model pathogen M. smegmatis by porphyrin-peptide conjugates

Porphyrin-peptide conjugates have a breadth of potential applications, including use in photodynamic therapy, boron neutron capture therapy, as fluorescence imaging tags for tracking subcellular localization, as magnetic resonance imaging (MRI) positive-contrast reagents and as biomimetic catalysts. Here, we have explored three general routes to porphyrin-peptide conjugates using the Cu(I)-catalyzed Huisgen-Medal-Sharpless 1,3-dipolar cycloaddition of peptide-containing azides with a terminal alkyne-containing porphyrin, thereby generating porphyrin-peptide conjugates (PPCs) comprised of a cationic porphyrin coupled to short antimicrobial peptides. In addition to characterizing the PPCs using a variety of spectroscopic (UV-vis, [Formula: see text]H- and [Formula: see text]C-NMR) and mass spectrometric methods, we evaluated their efficacy as photosensitizers for the in vitro photodynamic inactivation of Mycobacterium smegmatis as a model for the pathogen Mycobacterium tuberculosis. Difficulties that needed to be overcome for the efficient synthesis of PPCs were the limited solubility of the quaternized pyridyl porphyrin in common solvents, undesired (de)metallation and transmetallation, and chromatographic purification. Photodynamic inactivation studies of a small library of PPCs against Mycobacterium smegmatis confirmed our hypothesis that the porphyrin-based photosensitizer maintains its ability to efficiently inactivate bacteria when conjugated to a small peptide by upwards of 5–6 log units (99.999[Formula: see text]%) using white light illumination (400–700 nm, 60 mW/cm[Formula: see text], 30 min). Further, hemolysis assays revealed the lack of toxicity of the PPCs against sheep blood at concentrations employed for in vitro photodynamic inactivation. Taken together, the results demonstrated the ability of PPCs to maintain their antimicrobial photodynamic inactivation efficacy when possessing a short cationic peptides for enabling the potential targeting of pathogens in vivo.

Wool/Acrylic Blended Fabrics as Next-Generation Photodynamic Antimicrobial Materials

The adoption of self-sterilizing materials to reduce infection transmission in hospitals and related healthcare facilities has been hampered by the availability of scalable, cost-effective, and potent antimicrobial textiles. Here, we investigated whether photodynamic materials comprising photosensitizer-embedded wool/acrylic blends were able to mediate the photodynamic inactivation of Gram-positive and Gram-negative bacteria. A small library of wool/acrylic (W/A) blended fabrics was constructed wherein the wool fibers were embedded with rose Bengal (RB) as a photosensitizer and the acrylic fibers were dyed with a traditional cationic yellow X-8GL dye, thereby enabling a broader color palette than was achievable with a single photosensitizer. The resultant photodynamic materials were characterized by physical (SEM, DSC, TGA, tensile strength), spectroscopic (fluorescence), colorimetric (K/S and CIELab values), and color fastness (against rubbing, washing) studies, and their photooxidation of the model substrate potassium iodide demonstrated the ability of these materials to generate microbicidal reactive oxygen species (i.e., singlet oxygen) upon illumination. Our best results yielded the photodynamic inactivation of Gram-positive S. aureus (99.98%) and B. subtilis (99.993%) by ∼4 log units upon illumination with visible light (60 min; 65 ± 5 mW/cm²; λ ≥ 420 nm), although more modest activity was observed against Gram-negative P. aeruginosa and E. coli (1-2 log units pathogen reduction). While there were no statistically significant differences for dual-dyed materials that were produced through either sequential or simultaneous dyeing steps, it was noted that high loadings of the cationic yellow X-8GL dye did inhibit the antimicrobial activity of the RB photosensitizer, with the dual-dyed materials able to mediate a 2.9 log unit reduction against S. aureus at a 1% o.w.f X-8GL loading. These findings indicate that the antimicrobial photodynamic inactivation of dual-dyed materials is independent of the dyeing process itself, yet exhibits limitations on the loading of the traditional dye with regards to the activity of the photosensitizer. Taken together, the results suggest the feasibility of photosensitizer-embedded blended fabrics produced through a one-step dyeing process as a low-cost and scalable method for creating effective self-disinfecting textiles for infection prevention, and whose inclusion of a second traditional dye for color variation will further benefit their adoption from a commercial standpoint.

Trends and targets in antiviral phototherapy

Photodynamic therapy (PDT) is a well-established treatment option in the treatment of certain cancerous and pre-cancerous lesions. Though best-known for its application in tumor therapy, historically the photodynamic effect was first demonstrated against bacteria at the beginning of the 20^th century. Today, in light of spreading antibiotic resistance and the rise of new infections, this photodynamic inactivation (PDI) of microbes, such as bacteria, fungi, and viruses, is gaining considerable attention. This review focuses on the PDI of viruses as an alternative treatment in antiviral therapy, but also as a means of viral decontamination, covering mainly the literature of the last decade. The PDI of viruses shares the general action mechanism of photodynamic applications: the irradiation of a dye with light and the subsequent generation of reactive oxygen species (ROS) which are the effective phototoxic agents damaging virus targets by reacting with viral nucleic acids, lipids and proteins. Interestingly, a light-independent antiviral activity has also been found for some of these dyes. This review covers the compound classes employed in the PDI of viruses and their various areas of use. In the medical area, currently two fields stand out in which the PDI of viruses has found broader application: the purification of blood products and the treatment of human papilloma virus manifestations. However, the PDI of viruses has also found interest in such diverse areas as water and surface decontamination, and biosafety.

BODIPY-embedded electrospun materials in antimicrobial photodynamic inactivation

Drug-resistant pathogens, particularly those that result in hospital acquired infections (HAIs), have emerged as a critical priority for the World Health Organization. To address the need for self-disinfecting materials to counter the threat posed by the transmission of these pathogens from surfaces to new hosts, here we investigated if a cationic BODIPY photosensitizer, embedded via electrospinning into nylon and polyacrylonitrile (PAN) nanofibers, was capable of inactivating both bacteria and viruses via antimicrobial photodynamic inactivation (aPDI). Materials characterization, including fiber morphology and the degree of photosensitizer loading, was assessed by scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and UV-visible diffuse reflectance spectroscopy (UV-Vis DRS), and demonstrated that the materials were comprised of nanofibers (125-215 nm avg. diameter) that were thermostable to >300 °C. The antimicrobial potencies of the resultant Nylon-BODIPY⁽⁺⁾ and PAN-BODIPY⁽⁺⁾ nanofiber materials were evaluated against four strains of bacteria recognized by the World Health Organization as either critical or high priority pathogens: Gram-positive strains methicillin-resistant S. aureus (MRSA; ATCC BAA-44) and vancomycin-resistant E. faecium (VRE; ATCC BAA-2320), and Gram-negative strains multidrug-resistant A. baumannii (MDRAB; ATCC BAA-1605) and NDM-1 positive K. pneumoniae (KP; ATCC BAA-2146). Our results demonstrated the detection limit (99.9999%; 6 log units reduction in CFU mL^-1) photodynamic inactivation of three strains upon illumination (30-60 min; 40-65 ± 5 mW cm^-2; 400-700 nm): MRSA, VRE, and MDRAB, but only minimal inactivation (47-75%) of KP. Antiviral studies employing PAN-BODIPY⁽⁺⁾ against vesicular stomatitis virus (VSV), a model enveloped virus, revealed complete inactivation. Taken together, the results demonstrate the potential for electrospun BODIPY⁽⁺⁾-embedded nanofiber materials as the basis for pathogen-specific anti-infective materials, even at low photosensitizer loadings.

Photoinactivation of ESKAPE pathogens: overview of novel therapeutic strategy

The emergence of antimicrobial drug resistance requires development of alternative therapeutic options. Multidrug-resistant strains of Enterococcus spp., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumanii, Pseudomonas aeruginosa and Enterobacter spp. are still the most commonly identified antimicrobial-resistant pathogens. These microorganisms are part of the so-called 'ESKAPE' pathogens to emphasize that they currently cause the majority of hospital acquired infections and effectively 'escape' the effects of antibacterial drugs. Thus, alternative, safer and more efficient antimicrobial strategies are urgently needed, especially against 'ESKAPE' superbugs. Antimicrobial photodynamic inactivation is a therapeutic option used in the treatment of infectious diseases. It is based on a combination of a photosensitizer, light and oxygen to remove highly metabolically active cells.

Sunlight-Driven Wearable and Robust Antibacterial Coatings with Water-Soluble Cellulose-Based Photosensitizers

Herein, a simple, effective, and general strategy is demonstrated to obtain a water-soluble and nontoxic cellulose-based photosensitizer (CPS) with enhanced photodynamic antibacterial activity through introducing protoporphyrin IX (PpIX) and quaternary ammonium salt (QAS) groups onto the cellulose backbone. The synergistic effect of the anchoring and diluting effect of the cellulose backbone and the electrostatic repulsion between QAS groups effectively inhibit the π-π stacking of PpIX groups, thus the as-prepared CPS exhibits markedly enhanced reactive oxygen species (ROS) yield. Meanwhile, the positively charged QAS groups endow the CPS with water-solubility and a strong attractive force to bacteria. As a result, the CPS can rapidly and efficiently kill drug-resistant bacteria strains, including E. coli and S. aureus, with a low light dose (2.4 J cm^-2 ) and low concentration of PpIX groups (0.35 × 10^-6 m). Benefiting from the excellent processability and formability, the CPS is readily applied as a sunlight-driven wearable and robust antibacterial coating by a spray coating and later crosslinking procedure.

Chromium Cross-Linking Based Immobilization of Silver Nanoparticle Coating on Leather Surface with Broad-Spectrum Antimicrobial Activity and Durability

Leather with durable and broad-spectrum antimicrobial properties is very attractive in applications to produce diabetic shoes. In this work, gallic acid stabilized silver nanoparticles (GA@AgNPs) were prepared as water-borne finishing agent to be spray-coated on leather surface, with subsequent immobilization onto skin collagen via chromium(III) cross-linking. Such chemical anchoring of AgNPs onto microscaled collagen fibers not only enhanced the hydrophobicity of leather surface but also converted the surface ζ-potential from a positive charge to a negative charge, resulting in the excellent microbial antiadhesive ability of GA@AgNP-coated leather because of its dual-hydrophobic and electrostatic repelling of microbial adhesion. Such GA@AgNP coating also exhibited broad-spectrum antimicrobial activity against Escherichia coli, Staphylococcus aureus, methicillin-resistant S. aureus, and Candida albicans, with killing efficiencies all higher than 99%. Moreover, the killed microbes could be easily released from this anionic GA@AgNP spray coating by simply washing, preserving, and giving long-term antimicrobial activity to leather products. Most of all, the robust immobilization of AgNPs guaranteed the durably antimicrobial activity of such GA@AgNP-coated leather against laundry, perspiration, and mechanical abrasion in real daily use.

Zinc phthalocyanine activated by conventional indoor light makes a highly efficient antimicrobial material from regular cellulose

A phthalocyanine-cellulose material quickly inactivates drug-resistant microbes under indoor light.

Revisiting Current Photoactive Materials for Antimicrobial Photodynamic Therapy

Microbial infection is a severe concern, requiring the use of significant amounts of antimicrobials/biocides, not only in the hospital setting, but also in other environments. The increasing use of antimicrobial drugs and the rapid adaptability of microorganisms to these agents, have contributed to a sharp increase of antimicrobial resistance. It is obvious that the development of new strategies to combat planktonic and biofilm-embedded microorganisms is required. Photodynamic inactivation (PDI) is being recognized as an effective method to inactivate a broad spectrum of microorganisms, including those resistant to conventional antimicrobials. In the last few years, the development and biological assessment of new photosensitizers for PDI were accompanied by their immobilization in different supports having in mind the extension of the photodynamic principle to new applications, such as the disinfection of blood, water, and surfaces. In this review, we intended to cover a significant amount of recent work considering a diversity of photosensitizers and supports to achieve an effective photoinactivation. Special attention is devoted to the chemistry behind the preparation of the photomaterials by recurring to extensive examples, illustrating the design strategies. Additionally, we highlighted the biological challenges of each formulation expecting that the compiled information could motivate the development of other effective photoactive materials.