Enhancement of 5-aminolevulinic acid phototoxicity by encapsulation in polysaccharides based nanocomplexes for photodynamic therapy application

Utilizing a high-throughput visualization screening technology to develop a genetically encoded biosensor for monitoring 5-aminolevulinic acid production in engineered Escherichia coli

5-Aminolevulinic acid (5-ALA) is a non-protein amino acid widely used in agriculture, animal husbandry and medicine. Currently, microbial cell factories are a promising production pathway, but the lack of high-throughput fermentation strain screening tools often hinders the exploration of engineering strategies to increase cell factory yields. Here, mutant AC103-3H was screened from libraries of saturating mutants after response-specific engineering of the transcription factor AsnC of L-asparagine (Asn). Based on mutant AC103-3H, a whole-cell biosensor EAC103-3H with a specific response to 5-ALA was constructed, which has a linear dynamic detection range of 1-12 mM and a detection limit of 0.094 mM, and can be used for in situ screening of potential high-producing 5-ALA strains. With its support, overexpression of the C5 pathway genes using promoter engineering assistance resulted in a 4.78-fold enhancement of 5-ALA production in the engineered E. coli. This study provides an efficient strain screening tool for exploring approaches to improve the 5-ALA productivity of engineered strains.

A Review of the Efficacy of Nanomaterial-Based Natural Photosensitizers to Overcome Multidrug Resistance in Cancer

Natural photosensitizers (PS) are compounds derived from nature, with photodynamic properties. Natural PSs have a similar action to that of commercial PSs, where cancer cell death occurs by necrosis, apoptosis, and autophagy through ROS generation. Natural PSs have garnered great interest over the last few decades because of their high biocompatibility and good photoactivity. Specific wavelengths could cause phytochemicals to produce harmful ROS for photodynamic therapy (PDT). However, natural PSs have some shortcomings, such as reduced solubility and lower uptake, making them less appropriate for PDT. Nanotechnology offers an opportunity to develop suitable carriers for various natural PSs for PDT applications. Various nanoparticles have been developed to improve the outcome with enhanced solubility, optical adsorption, and tumor targeting. Multidrug resistance (MDR) is a phenomenon in which tumor cells develop resistance to a wide range of structurally and functionally unrelated drugs. Over the last decade, several researchers have extensively studied the effect of natural PS-based photodynamic treatment (PDT) on MDR cells. Though the outcomes of clinical trials for natural PSs were inconclusive, significant advancement is still required before PSs can be used as a PDT agent for treating MDR tumors. This review addresses the increasing literature on MDR tumor progression and the efficacy of PDT, emphasizing the importance of developing new nano-based natural PSs in the fight against MDR that have the required features for an MDR tumor photosensitizing regimen.

ALA/Ag2S/MnO2 Hybrid Nanoparticles for Near-Infrared Image-Guided Long-Wavelength Phototherapy of Breast Cancer

The combination of photothermal therapy (PTT) and photodynamic therapy (PDT) based on temperature increase and the formation of reactive oxygen species (ROS), respectively, is an exciting avenue to provide local and improved therapy of tumors with minimal off-site toxicity. 5-Aminolevulinic acid (ALA) is one of the most popular PDT pro-drugs, and its efficiency improves significantly when delivered to tumors with nanoparticles (NPs). But the tumor site's hypoxic environment is a handicap for the oxygen-consuming PDT process. In this work, highly stable, small, theranostic NPs composed of Ag₂S quantum dots and MnO₂, electrostatically loaded with ALA, were developed for enhanced PDT/PTT combination of tumors. MnO₂ catalyzes endogenous H₂O₂ to O₂ conversion and glutathione depletion, enhancing ROS generation and ALA-PDT efficiency. Ag₂S quantum dots (AS QDs) conjugated with bovine serum albumin (BSA) support MnO₂ formation and stabilization around Ag₂S. AS-BSA-MnO₂ provided a strong intracellular near-infrared (NIR) signal and increased the solution temperature by 15 °C upon laser irradiation at 808 nm (215 mW, 10 mg/mL), proving the hybrid NP as an optically trackable, long-wavelength PTT agent. In the in vitro studies, no significant cytotoxicity was observed in the absence of laser irradiation in healthy (C2C12) or breast cancer cell lines (SKBR3 and MDA-MB-231). The most effective phototoxicity was observed when AS-BSA-MnO₂-ALA-treated cells were co-irradiated for 5 min with 640 nm (300 mW) and 808 nm (700 mW) due to enhanced ALA-PDT combined with PTT. The viability of cancer cells decreased to approximately 5-10% at 50 μg/mL [Ag], corresponding to 1.6 mM [ALA], whereas at the same concentration, individual PTT and PDT treatments decreased the viability to 55-35%, respectively. The late apoptotic death of the treated cells was mostly correlated with high ROS levels and lactate dehydrogenase. Overall, these hybrid NPs overcome tumor hypoxia, deliver ALA to tumor cells, and provide both NIR tracking and enhanced PDT + PTT combination therapy upon short, low-dose co-irradiation at long wavelengths. These agents that may be utilized for treating other cancer types are also highly suitable for in vivo investigations.

Photodynamic Therapy for the Treatment of Fungal Infections

Cutaneous fungal infections are common in humans and are associated with significant physical and psychological distress to patients. Although conventional topical and/or oral anti-fungal medications are commonly recommended treatments, drug resistance has emerged as a significant concern in this patient population, and safer, more efficacious, and cost-effective alternatives are warranted. Recent studies have reported effectiveness of photodynamic therapy (PDT) against fungal infections without severe adverse effects. In this review, we briefly discuss the mechanisms underlying PDT, current progress, adverse effects, and limitations of this treatment in the management of superficial and deep fungal infections.

Chitosan/hyaluronan nanogels co-delivering methotrexate and 5-aminolevulinic acid: A combined chemo-photodynamic therapy for psoriasis

Psoriasis does not respond adequately to the monotherapy, tailoring combined strategies for synergistical treatment remains challenging. We fabricated chitosan/hyaluronan nanogels to co-load methotrexate (MTX) and 5-aminoleavulinic acid (ALA), i.e., MTX-ALA NGs, for a combined chemo-photodynamic therapy for psoriasis. Compared with MTX-ALA suspension, the NGs enhanced the penetration and retention of MTX and ALA through and into the skin in vitro and in vivo (p < 0.001). NGs enhanced the cellular uptake (p < 0.001), protoporphyrin IX conversion (p < 0.001), and reactive oxygen species generation (3.93-fold), subsequently exerted the synergistical anti-proliferation and apoptosis on lipopolysaccharide-irritated HaCaT cells with the apoptosis rate of 78.6%. MTX-ALA NGs efficiently ameliorated the skin manifestations and down-regulated the proinflammatory cytokines of TNF-α and IL-17A in imiquimod-induced psoriatic mice (p < 0.001). Importantly, MTX-ALA NGs reduced the toxicities of oral MTX to the liver and kidney. The results support that MTX-ALA NG is a convenient, effective, and safe combined chemo-photodynamic strategy for psoriasis treatment.

Transferrin receptors/magnetic resonance dual-targeted nanoplatform for precise chemo-photodynamic synergistic cancer therapy

Various drug delivery strategies to improve cancer therapeutic efficacy have been actively investigated. One major challenge is to improve the targeting ability. Here elaborately designed nanocarriers (NCs) named as Tf-5-ALA-PTX-NCs are demonstrated to address this problem. In this nanostructure, paclitaxel (PTX) and 5-aminolevulinic acid (5-ALA) were co-encapsulated within magnetic nanocarriers to achieve synergistic chemotherapy and photodynamic therapy, while transferrin (Tf) was conjugated with modified copolymer Pluronic P123 and embedded in the surface of the nanocarriers, which endows nanocarriers with Tf targeting and magnetic targeting to enhance the anti-tumor outcome. Results demonstrated that Tf-5-ALA-PTX-NCs significantly enhanced the targeting drug delivery to MCF-7 cells and synergistically induced apoptosis and death of MCF-7 cells in vitro and highly efficient tumor ablation in vivo. Intriguingly, Tf-5-ALA-PTX-NCs have a controllable "on/off" switch to enhance the drug release. The dual-targeted nanocarriers would be a promising versatile anti-tumor drug delivery and imaging-guided cancer chemo-photodynamic synchronization therapy strategy.

Cetuximab-Ag2S quantum dots for fluorescence imaging and highly effective combination of ALA-based photodynamic/chemo-therapy of colorectal cancer cells

Colorectal cancer (CRC) has a poor prognosis and urgently needs better therapeutic approaches. 5-Aminolevulinic acid (ALA) induced protoporphyrin IX (PpIX) based photodynamic therapy (PDT) is already used in the clinic for several cancers but not yet well investigated for CRC. Currently, systemic administration of ALA offers a limited degree of tumour selectivity, except for intracranial tumours, limiting its wider use in the clinic. The combination of effective ALA-PDT and chemotherapy may provide a promising alternative approach for CRC treatment. Herein, theranostic Ag₂S quantum dots (AS-2MPA) optically trackable in near-infrared (NIR), conjugated with endothelial growth factor receptor (EGFR) targeting Cetuximab (Cet) and loaded with ALA for PDT monotherapy or ALA/5-fluorouracil (5FU) for the combination therapy are proposed for enhanced treatment of EGFR(+) CRC. AS-2MPA-Cet exhibited excellent targeting of the high EGFR expressing cells and showed a strong intracellular signal for NIR optical detection in a comparative study performed on SW480, HCT116, and HT29 cells, which exhibit high, medium and low EGFR expression, respectively. Targeting provided enhanced uptake of the ALA loaded nanoparticles by strong EGFR expressing cells and formation of higher levels of PpIX. Cells also differ in their efficiency to convert ALA to PpIX, and SW480 was the best, followed by HT29, while HCT116 was determined as unsuitable for ALA-PDT. The therapeutic efficacy was evaluated in 2D cell cultures and 3D spheroids of SW480 and HT29 cells using AS-2MPA with either electrostatically loaded, hydrazone or amide linked ALA to achieve different levels of pH or enzyme sensitive release. Most effective phototoxicity was observed in SW480 cells using AS-2MPA-ALA-electrostatic-Cet due to enhanced uptake of the particles, fast ALA release and effective ALA-to-PpIX conversion. Targeted delivery reduced the effective ALA concentration significantly which was further reduced with codelivery of 5FU. Delivery of ALA via covalent linkages was also effective for PDT, but required a longer incubation time for the release of ALA in therapeutic doses. Phototoxicity was correlated with high levels of reactive oxygen species (ROS) and apoptotic/necrotic cell death. Hence, both AS-2MPA-ALA-Cet based PDT and AS-2MPA-ALA-Cet-5FU based chemo/PDT combination therapy coupled with strong NIR tracking of the nanoparticles demonstrate an exceptional therapeutic effect on CRC cells and excellent potential for synergistic multistage tumour targeting therapy.

pH-Sensitive Folic Acid Conjugated Alginate Nanoparticle for Induction of Cancer-Specific Fluorescence Imaging

In cancer nanomedicine, numerous studies have been conducted on the surface modification and transport capacity of nanoparticles (NPs); however, biological barriers, such as enzymatic degradation or non-specific delivery during circulation, remain to be cleared. Herein, we developed pH-sensitive NPs that degrade in an acidic environment and release 5-aminolevulinic acid (5ALA) to the target site. NPs were prepared by conjugating alginate with folic acid, followed by encapsulation of 5ALA through a water-in-oil (W/O) emulsion method. The alginate-conjugated folic acid nanoparticles (AF NPs) were homogeneous in size, stable for a long time in aqueous suspension without aggregation, and non-toxic. AF NPs were small enough to efficiently infiltrate tumors (<50 nm) and were specifically internalized by cancer cells through receptor-mediated endocytosis. After the intracellular absorption of NPs, alginate was deprotonated in the lysosomes and released 5ALA, which was converted to protoporphyrin IX (PpIX) through mitochondrial heme synthesis. Our study outcomes demonstrated that AF NPs were not degraded by enzymes or other external factors before reaching cancer cells, and fluorescent precursors were specifically and accurately delivered to cancer cells to generate fluorescence.

Solubilization of Hexyl Aminolevulinate by Surfactants for Tumor Fluorescence Detection

Hexyl aminolevulinate (HAL) is a lipophilic derivative of 5-aminolevulinic acid (5-ALA) and can induce more protoporphyrin IX (PpIX) formation and stronger fluorescence intensity (FI) than 5-ALA, which will greatly facilitate photodynamic diagnosis and therapy. The main drawback of HAL is its low solubility in neutral aqueous media. In this study, surfactants were used to increase HAL solubility in the cell culture medium and serum, followed by in vitro fluorescence formation measurement in human pancreatic cancer cells (SW1990) and in vivo fluorescence detection in tumor-bearing mice. The results showed that Tween 80 (TW80) and Kolliphor® HS 15 (HS15) increased the solubility of HAL in the selected media. Although TW80 and HS15 exhibited in vitro cytotoxicity at high concentrations (5 mg mL^-1 ), they facilitated fluorescent signal formation at the early stage of cell incubation. When surfactants were used, the FI should be determined without the routine washing process because surfactant-containing culture medium caused the loss of synthesized PpIX during the washing process. When HAL dissolved in TW80 solution was injected intraperitoneally into pancreatic cancer-bearing mice at a dose of 50 mg kg^-1 , the tumors exhibited red fluorescence, which indicated that systemic administration of surfactant-solubilized HAL might be applicable for tumor fluorescence detection in vivo.

Photodynamic therapy combined with antifungal drugs against chromoblastomycosis and the effect of ALA-PDT on Fonsecaea in vitro

Background

Chromoblastomycosis is a chronic skin and subcutaneous fungal infection caused by dematiaceous fungi and is associated with low cure and high relapse rates. In southern China, Fonsecaea monophora and Fonsecaea pedrosoi are the main causative agents.

Principal findings

We treated 5 refractory and complex cases of chromoblastomycosis with 5-aminolevulinic acid photodynamic therapy (ALA-PDT) combined with oral antifungal drugs. The lesions improved after 4 to 9 sessions of ALA-PDT treatment at an interval of one or two weeks, and in some cases, mycological testing results became negative. The isolates were assayed for susceptibility to antifungal drugs and ALA-PDT in vitro, revealing sensitivity to terbinafine, itraconazole and voriconazole, with ALA-PDT altering the cell wall and increasing reactive oxygen species production.

Conclusions

These results provide the basis for the development of a new therapeutic approach, and ALA-PDT combined with oral antifungal drugs constitutes a promising alternative method for the treatment of refractory and complex cases of chromoblastomycosis.

Chromoblastomycosis, a neglected tropical disease, is one of the most frequently encountered subcutaneous mycoses. The disease is usually caused by traumatic inoculation of a specific group of dematiaceous fungi. Chromoblastomycosisis characterized by slowly expanding skin lesions and is associated with low cure and high relapse rates. In recent years, effective methods, such as photodynamic therapy (PDT), have been employed for inhibiting the pathogen’s activity. The authors treated 5 refractory and complex cases of chromoblastomycosis with 5-aminolevulinic acid photodynamic therapy (ALA-PDT) combined with oral antifungal drugs. The lesions improved after 4 to 9 sessions of ALA-PDT treatment at an interval of one or two weeks, and in some cases, mycological testing results became negative. The authors also found that ALA-PDT alter the fungi cell wall and increase reactive oxygen species production. This research provides the basis for the development of a new therapeutic approach, and ALA-PDT combined with oral antifungal drugs constitutes a promising alternative method for the treatment of refractory and complex cases of chromoblastomycosis.

Branched poly (lactic acid) microparticles for enhancing the 5-aminolevulinic acid phototoxicity

An innovative microcarrier based on a carboxy-enriched and branched polylactic acid derivative was developed to enhance the in vitro phototoxicity of the photosensitizer and prodrug 5-aminolevulinic. Microparticles, prepared by double emulsion technique and loaded with the prodrug were carefully characterized and the effect of the polymer structure on the chemical, physical and biological properties of the final product was evaluated. Results showed that microparticles have a spherical shape and ability to allocate up to 30 μg of the photosensitizer per mg of carrier despite their difference in solubility. Release studies performed in various simulated physiological conditions demonstrate the influence of the branched structure and the presence of the additional carboxylic groups on the release rate and the possibility to modulate it. In vitro assays conducted on human epithelial adenocarcinoma cells proved the not cytotoxicity of the carriers in a wide range of concentrations. The hemocompatibility and surface proteins adsorption were evaluated at different microparticles concentrations to evaluate the safety and estimate the possible microparticles residential time in the bloodstream. The advantages, of loading 5-aminolevulinic acid in the prepared carrier has been deeply described in terms of enhanced phototoxicity, compared to the free 5-aminolevulinic acid formulation after irradiation with light at 635 nm. The obtained results demonstrate the advantages of the prepared derivative compared to the linear polylactide for future application in photodynamic therapy based on the photosensitizer 5-aminolevulinic acid.

Nanoparticles based on glycyrrhetinic acid modified porphyrin for photodynamic therapy of cancer

Nanoparticles were prepared from amphiphilic glycyrrhetinic acid–porphyrin conjugates (TPP–GA) and applied for the photodynamic therapy of cancer.