Hydrothermal derived protoporphyrin IX nanoparticles for inactivation and imaging of bacteria strains

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.

Alkylated EDTA potentiates antibacterial photodynamic activity of protoporphyrin

Antibiotic resistance has garnered significant attention due to the scarcity of new antibiotics in development. Protoporphyrin IX (PpIX)-mediated photodynamic therapy shows promise as a novel antibacterial strategy, serving as an alternative to antibiotics. However, the poor solubility of PpIX and its tendency to aggregate greatly hinder its photodynamic efficacy. In this study, we demonstrate that alkylated EDTA derivatives (aEDTA), particularly C14-EDTA, can enhance the solubility of PpIX by facilitating its dispersion in aqueous solutions. The combination of C14-EDTA and PpIX exhibits potent antibacterial activity against Staphylococcus aureus (S. aureus) when exposed to LED light irradiation. Furthermore, this combination effectively eradicates S. aureus biofilms, which are known to be strongly resistant to antibiotics, and demonstrates high therapeutic efficacy in an animal model of infected ulcers. Mechanistic studies reveal that C14-EDTA can disrupt PpIX crystallization, increase bacterial membrane permeability and sequester divalent cations, thereby improving the accumulation of PpIX in bacteria. This, in turn, enhances reactive oxygen species (ROS) production and the antibacterial photodynamic activity. Overall, this effective strategy holds great promise in combating antibiotic-resistant strains.

Bimodal Antimicrobial Surfaces of Phytic Acid-Prussian Blue Nanoparticles-Cationic Polymer Networks

Surface modification plays a pivotal role in tailoring the functionalities of a solid material. Introduction of antimicrobial function on material surfaces can provide additional protection against life-threatening bacterial infections. Herein, a simple and universal surface modification method based on surface adhesion and electrostatic interaction of phytic acid (PA) is developed. PA is first functionalized with Prussian blue nanoparticles (PB NPs) via metal chelation and then conjugates with cationic polymers (CPs) through electrostatic interaction. With the aid of surface adherent PA and gravitation effect, the as-formed PA-PB-CP network aggregates are deposited on the solid materials in a substrate-independent manner. Synergistic bactericidal effects of "contact-killing" induced by the CPs and localized photothermal effect caused by the PB NPs endow the substrates with strong antibacterial performance. Membrane integrity, enzymatic activity, and metabolism function of the bacteria are disturbed in contact with the PA-PB-CP coating under near-infrared (NIR) irradiation. The PA-PB-CP modified biomedical implant surfaces exhibit good biocompatibility and synergistic antibacterial effect under NIR irradiation, and eliminate the adhered bacteria both in vitro and in vivo.

Recent advances in engineered polymeric materials for efficient photodynamic inactivation of bacterial pathogens

Nowadays, infectious diseases persist as a global crisis by causing significant destruction to public health and the economic stability of countries worldwide. Especially bacterial infections remain a most severe concern due to the prevalence and emergence of multi-drug resistance (MDR) and limitations with existing therapeutic options. Antibacterial photodynamic therapy (APDT) is a potential therapeutic modality that involves the systematic administration of photosensitizers (PSs), light, and molecular oxygen (O₂) for coping with bacterial infections. Although the existing porphyrin and non-porphyrin PSs were effective in APDT, the poor solubility, limited efficacy against Gram-negative bacteria, and non-specific distribution hinder their clinical applications. Accordingly, to promote the efficiency of conventional PSs, various polymer-driven modification and functionalization strategies have been adopted to engineer multifunctional hybrid phototherapeutics. This review assesses recent advancements and state-of-the-art research in polymer-PSs hybrid materials developed for APDT applications. Further, the key research findings of the following aspects are considered in-depth with constructive discussions: i) PSs-integrated/functionalized polymeric composites through various molecular interactions; ii) PSs-deposited coatings on different substrates and devices to eliminate healthcare-associated infections; and iii) PSs-embedded films, scaffolds, and hydrogels for regenerative medicine applications.

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Synthetic strategies of engineered polymer-based hybrid materials integrated with photosensitizers for APDT.

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Utilization of photosensitizer-incorporated polymeric materials in health care applications.

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Challenges and opportunities in the future development of polymeric biomaterials with improved photo-bactericidal properties.

Antimicrobial photodynamic inactivation of wastewater microorganisms by halogenated indole derivative capped zinc oxide

Novel 5-bromoindole (5B)-capped zinc oxide (ZnO) nanoparticles (5BZN) were synthesized to improve the antibacterial, antibiofilm, and disinfection processes for the control of microorganisms in wastewater treatment. When exposed to 5BZN, the biofilm density and cell attachment were reduced dramatically, as measured by scanning electron microscopy (SEM). The 5BZN were also investigated for photodynamic treatment of multidrug-resistant (MDR) bacteria and toxicity. The combination of 5B and ZnO exhibited strong antibacterial and antibiofilm activities against MDR bacteria even at low doses (20 μg/mL). After 12.5 mW/cm² blue LED irradiation, the composite 5BZN showed superior photodynamic inactivation of two wastewater MDR, Enterobacter tabaci E2 and Klebsiella quasipneumoniae SC3, with cell densities reduced by 3.9 log CFU/mL and 4.7 log CFU/mL, respectively, after 120 min. The mechanism of bacterial inactivation was studied using a scavenging investigation, and H₂O₂ was identified mainly as the reactive species for bacterial inactivation. The 5BZN exhibited higher photodynamic inactivation towards the total coliform bacteria in wastewater effluents under a blue LED light intensity of 12.5 mW/cm² with almost complete inactivation of the coliform bacteria cells within 40 min. Furthermore, when 5BZN (100 mg/L) was added to the reactor, the level of tetracycline antibiotic degradation was increased by 63.6% after 120 min. The toxicity test, animal model nematode studies and seed germination assays, showed that 5BZN is harmless, highlighting its tremendous potential as a self-healing agent in large-scale photodynamic disinfection processes.

Cationic porphyrin-based nanoparticles for photodynamic inactivation and identification of bacteria strains

The emergence of antibiotic drug resistance has undermined the efficacy of antibiotics, and is becoming a severe threat to public health. To combat antibiotic drug resistance and to replace traditional antibiotic treatment, an alternative strategy based on antibacterial photodynamic therapy (APDT), which has broad applicability, high efficiency and less potential of developing antibiotic drug resistance, has been developed. In this work, the cationic porphyrin-based nanoparticles (NPs) were prepared by epoxy-amine chain extension polymerization of diepoxy-terminated poly(ethylene glycol) (PEG) and tetraamino-containing porphyrin, followed by quaternization with methyl iodine and butyl bromide. The as-obtained cationic porphyrin NPs preserved the photophysical properties of porphyrin derivatives, and can efficiently generate singlet oxygen (¹O₂) under 635 nm laser irradiation. The cationic porphyrin-based NPs displayed intrinsic antibacterial properties, and exhibited strong APDT effect on Gram-positive bacteria by destroying the bacterial cell membranes. Upon incubation with different bacterial strains, it was found that they could be utilized to identify Gram-positive bacteria by observing the sedimentation behavior of their mixtures, and visualizing their co-cultured and centrifugal bacteria cakes. In addition, the cationic porphyrin-based NPs had good hemocompatibility and low dark cytotoxicity.

Visible light-driven photoelectrocatalysis for simultaneous removal of oxytetracycline and Cu (II) based on plasmonic Bi/Bi2O3/TiO2 nanotubes

A visible light-driven photoelectrocatalytic system was constructed based on Bi/Bi₂O₃/TiO₂ nanotubes (NTs) to treat wastewater containing oxytetracycline and Cu²⁺ mixed pollutants. The surface morphology, crystal phase, elemental composition, light absorption property and photoelectrochemical activity of the synthesized Bi/Bi₂O₃/TiO₂ NTs were investigated. The composite film, Bi/Bi₂O₃/TiO₂ NTs was used for the photoelectrochemical removal of oxytetracycline, and it had excellent visible light photoelectrocatalytic performance. Under optimal conditions, the composite film was simultaneously used to remove coexisting oxytetracycline-Cu²⁺. The study results show that the reduction of Cu²⁺ on cathode was promoted by oxytetracycline while the degradation of oxytetracycline on photoanode was slightly suppressed by Cu²⁺. Also, possible photoelectrocatalytic degradation pathways for oxytetracycline-Cu²⁺ were analyzed by HPLC-MS.

Vancomycin-Functionalized Porphyrinic Metal-Organic Framework PCN-224 with Enhanced Antibacterial Activity against Staphylococcus Aureus

A vancomycin (Van) modification strategy on a porphyrinic metal-organic framework (MOF) PCN-224 is presented. The obtained Van-PCN-224 gives the combined advantages of porphyrinic MOF and Van with high photosensitive activity and excellent targeted antibacterial activity against Staphylococcus aureus. The features make Van-PCN-224 promising for antimicrobial therapy.

Protoporphyrin IX (PpIX) loaded PLGA nanoparticles for topical Photodynamic Therapy of melanoma cells

INTRODUCTION

Nanoparticles (Np) can increase drug efficacy and overcome problems associated with solubility and aggregation in a solution of PpIX.

PURPOSE

Evaluate if Np interferes in the photophysical and photobiological capacity of the PpIX comparing with free PpIX intended for topical PDT of melanoma.

METHODS

In vitro photophysical evaluation of Np-PpIX was carried out through singlet oxygen (₁O²) quantum yield. In vitro cytotoxicity and phototoxicity assays have used murine melanoma cell culture.

RESULTS

The quantum yield of singlet oxygen has shown that Np did not influence the formation capacity of this reactive species. In the dark, all PpIX-Nps concentrations were less cytotoxic compared to free drugs. At a higher light dose (1500 mJ.cm²) 3.91 μg / mL PpIX had similar % viable cells for free and Np (∼34 %) meaning Nps did not interfere in the photodynamic effect of PpIX. However, at 7.91 μg / mL the phototoxicity increased for both (5.8 % viable cells for free versus 21.7 % for Nps). Despite the higher phototoxicity of free PpIX at this concentration, greater cytotoxicity in the dark was obtained (∼49 % viable cells for free versus ∼90.6 % Np) which means Nps protect the tumor tissue from the photodynamic action of PpIX.

CONCLUSIONS

Np is a potential delivery system for melanoma skin cancer, since it maintained the photophysical properties of PpIX and excellent in vitro phototoxicity effect against melanoma cells, reducing cell viability ∼80 % (7.91 μg / mL PpIX in Nps) and provides safe PDT (due to lower cytotoxicity in the dark).

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.

Enhanced photodynamic inactivation for Gram-negative bacteria by branched polyethylenimine-containing nanoparticles under visible light irradiation

Antibiotic pollution has been a serious global public health concern in recent years, photodynamic inactivation is one of the most promising and innovative methods for antibacterial applications that avoids antibiotic abuse and minimizes risks of antibiotic resistance. However, limited by the weak interaction between the photosensitizers and Gram-negative bacteria, the effect of photodynamic inactivation cannot be fully exerted. Herein, photosensitizer chlorin e6-loaded polyethyleneimine-based micelle was constructed. The synergy of electrostatic and hydrophobic interactions between the nanoparticles and the bacterial surface promoted the anchoring of nanoparticles onto the bacteria, resulting in enhanced photoinactivation activities on Gram-negative bacteria. As expected, an eminent antibacterial effect was also observed on the Gram-positive bacteria Staphylococcus aureus. The cellular uptake results showed that photosensitizer was firmly anchored to the bacterial cell surface of Escherichia coli or Staphylococcus aureus by the introduction of branched polyethylenimine-containing nanoparticles. The light-triggered generation of reactive oxygen species, mainly singlet oxygen, from the membrane-bound nanoparticles caused irreversible damage to the bacterial outer membrane, achieving enhanced bactericidal efficiency than free photosensitizer. The study would provide an efficient and promising antimicrobial alternative to prevent overuse of antibiotics and have enormous potential for human healthcare and the environment remediation.

Fast and High-Throughput Evaluation of Photodynamic Effect by Monitoring Specific Protein Oxidation with MALDI-TOF Mass Spectrometry

In antibacterial practices by photodynamic treatment, bacteria are incubated with photosensitizers and then oxidized to death by generating reactive oxygen species (ROS) under light irradiation. Generally, Luria-Bertani (LB) agar colony is a conventional method to evaluate the photodynamic effect. However, this method is time consuming, easily disturbed by pollutants, and limited to the analysis of a pure bacteria sample. Herein, we introduce a novel method of photodynamic effect evaluation through in situ detection of specific protein oxidation by matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) with only 1 μL of sample in a fast (less than 1 min per sample) and high-throughput (up to 384 samples per run) way. The oxidation rates of specific proteins stayed highly consistent with bactericidal rates and thus MALDI-TOF MS might be able to replace the LB agar colony to evaluate the photodynamic effect. With the present method, several experimental conditions including different photosensitizer types, dosage controls, and different illumination times were easily screened to optimize photodynamic effect. Photodynamic effects of various bacteria species, cancer cells, and even mixture samples were also evaluated. The results demonstrate the promising application of MALDI-TOF MS in evaluating the photodynamic effect of each component in a mixture sample without any separation or purification, which could not be achieved by the traditional LB agar colony method.

Insight into light-driven antibacterial cotton fabrics decorated by in situ growth strategy

Development of ease-fabricated and effectively self-disinfecting textile materials for antimicrobial and infection prevention has been urgently desired by both consumers and industry. However, some nonresponsive antibacterial agents finished fabrics may be harmful to human. To address this issue, we developed a facile finishing method to endow woven cotton fabrics (WCF) with light-driven antibacterial property. Here in, porphyrinic metal-organic frameworks (PCN-224) were in situ synthesized on WCF (termed PCN-224/WCF) and PCN-224/WCF was proven to be used for antibacterial photodynamic inactivation (aPDI). aPDI studies indicated no difference in bacterial inactivation, the inactivation was 99.9999% of Gram-negative Escherichia coli 8099 and Pseudomonas aeruginosa CMCC (B) 10104 as well as Gram-positive Staphylococcus aureus ATCC-6538 and Bacillus subtilis CMCC (B) 63501 under visible light illumination (500 W, 15 cm vertical distance, λ ≥ 420 nm, 45 min). Cytotoxicity tests revealed PCN-224/WCF had low biological toxicity and good biocompatibility. Mechanism study revealed that singlet oxygen (¹O₂) was produced by PCN-224/WCF and caused severe damage to bacteria which was observed from the SEM images. This study provided a facile guideline to functionalize cotton fabrics with responsive bactericidal property which showed great potential for new generation of textiles with practical applications.

Silver-decorated, light-activatable polymeric antimicrobials for combined chemo-photodynamic therapy of drug-resistant bacterial infection

In this article, we describe a silver-decorated, light-activatable polymeric antimicrobial with strong synergistic chemo-photodynamic effect to combat bacterial infections.

Nanocarriers in photodynamic therapy-in vitro and in vivo studies

Photodynamic therapy (PDT) is a minimally invasive technique which has proven to be successful in the treatment of several types of tumors. This relatively simple method exploits three inseparable elements: phototoxic compound (photosensitizer [PS]), light source, and oxygen. Upon irradiation by light with specified wavelength, PS generates reactive oxygen species, which starts the cascade of reactions leading to cell death. The positive therapeutic outcome of PDT may be limited due to several aspects, including low water solubility of PSs, hampering their effective administration and blood circulation, as well as low tumor specificity, inefficient cellular uptake and activation energies requiring prolonged illumination times. One of the promising approaches to overcome these obstacles involves the use of carrier systems modulating pharmacokinetics and pharmacodynamics of the PSs. In the present review, we summarized current in vitro and in vivo studies regarding the use of nanoparticles as potential delivery devices for PSs to enhance their cellular uptake and cytotoxic properties, and thus-the therapeutic outcome of PDT. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Carbon dot-DNA-protoporphyrin hybrid hydrogel for sustained photoinduced antimicrobial activity

An assembly of hybrid hydrogel derived from Carbon Dot (CD), Protoporphyrin IX (PpIX) and DNA is reported here. PpIX and CD were covalently conjugated to 5'-phosphate termini of Cytosine (C) rich single strand DNA (ssDNA) separately. The CD-DNA-PpIX hybrid hydrogel was assembled through the formation of intercalated motif (i-motif) DNA network structure from CD-DNA and PpIX-DNA conjugates where CD act as crosslinkers in the hydrogel as well as energy donor to excite the photosensitizer (PS), PpIX. While hydrogel derived from only PpIX-DNA conjugate showed an inadequate sol-gel transition, the same could be precisely achieved from the CD-DNA-PpIX hybrid hydrogel by controlled pH adjustment. Distinct photophysical properties of CD and PpIX including fluorescence emission potentially enable tracking of the PS loading and hydrogel dissolution that was visually detectable under UV illumination. Reactive Oxygen Species (ROS) generation and subsequent killing of gram-positive bacteria (Staphylococcus aureus (S. aureus)) were observed following excitation of PpIX (acceptor) in the hybrid hydrogel either through energy transfer from CD or by direct irradiation of PpIX with visible light. Complete dissolution of hydrogel and sustained release of PpIX and subsequent ROS generation was achieved over 10-11 days that could kill S. aureus systematically. This study provides a promising strategy to address self-quenching and solubility of PS for its sustained release in Antimicrobial Photodynamic Therapy (A-PDT) applications through smart hydrogel formulation.

A maltoheptaose-decorated BODIPY photosensitizer for photodynamic inactivation of Gram-positive bacteria

A maltoheptaose-decorated BODIPY with high singlet oxygen generation efficacy was synthesized for photodynamic inactivation of Gram-positive bacteria in planktonic forms and biofilms.