In vitro investigation of methylene blue-bearing, electrostatically assembled aptamer–silica nanocomposites as potential photodynamic therapeutics

Novel Application of Photo-Crosslinked Urocanic-Acid-Modified Chitosan in Corneal Wounds

In the last few years, the use of tissue adhesives in corneal perforation has gained immense popularity in clinical practices. The present study aimed to devise a new application of urocanic-acid-modified chitosan (CS) with methylene blue (MB) as a photosensitizer for the development of a photo-crosslinked tissue adhesive. In particular, the curing time was controlled with the aid of a 650 nm red diode. Under the same irradiation condition, the mechanical properties were tuned using the photosensitizer at different concentrations. In vitro tests revealed that the gel was ductile and biocompatible. The application of the gel to a perforated cornea model stopped the leakage of aqueous humor, immediately after the gel was photo-crosslinked. The blue appearance of the gel provided high precision when applied to corneal wounds. Importantly, the crosslinked gel became transparent within 24 h, owing to the dissipation of MB from tears, and the gel spontaneously sloughed off without artificial removal. Altogether, the study reported the development of a novel photo-crosslinkable urocanic-acid-modified CS gel that exhibited significant potential to be utilized in the healing of corneal perforation.

Stable Encapsulation of Methylene Blue in Polysulfide Organosilica Colloids for Fluorescent Tracking of Nanoparticle Uptake in Cells

Methylene blue (MB), a century-old drug and a fluorescent dye, has a long history of diverse applications, both in drug therapy and as a tissue-staining agent. However, MB is inherently unstable when exposed to light and reducing agents. In this study, we aim to prepare and characterize polysulfide-based organosilica colloidal particles for efficient, stable, and protective encapsulation of MB. Disulfide- and tetrasulfide-containing organosilane congeners were used as organosilica precursors for direct synthesis of organosilica colloids based on the silica ouzo effect. MB was spontaneously entrapped into the colloidal particles during the particle formation process. The following properties of the colloidal MB were evaluated: particle size, surface charge, atomic distribution, encapsulation efficiency, MB release, photodynamic activity, thiol and ascorbate reactivity, and cytotoxicity. The DLS measurements show that the size of colloidal MB is tunable in a range of 100 nm to 1 μm. SEM images reveal spherical particles with composition-dependent particle sizes of 70-120 nm (coefficient of variation: 15-18%). MB was encapsulated in the colloidal particles with a maximal efficiency of 95%. The release of MB from the colloids was <1% at 4 h and <3.5% at 48 h. The colloidal particles show much reduced photodynamic activity, low reactivity toward reducing agents, and low cytotoxicity. Accordingly, the colloidal MB was proposed and further investigated as a fluorescent particle tracer for the study of cell-nanoparticle interactions. In conclusion, MB can be efficiently and stably loaded into polysulfide organosilica colloidal particles using a simple and convenient physical route.

Overcoming barriers in photodynamic therapy harnessing nano-formulation strategies

Photodynamic therapy (PDT) has been extensively investigated for decades for tumor treatment because of its non-invasiveness, spatiotemporal selectivity, lower side-effects, and immune activation ability. It can be a promising treatment modality in several medical fields, including oncology, immunology, urology, dermatology, ophthalmology, cardiology, pneumology, and dentistry. Nevertheless, the clinical application of PDT is largely restricted by the drawbacks of traditional photosensitizers, limited tissue penetrability of light, inefficient induction of tumor cell death, tumor resistance to the therapy, and the severe pain induced by the therapy. Recently, various photosensitizer formulations and therapy strategies have been developed to overcome these barriers. Significantly, the introduction of nanomaterials in PDT, as carriers or photosensitizers, may overcome the drawbacks of traditional photosensitizers. Based on this, nanocomposites excited by various light sources are applied in the PDT of deep-seated tumors. Modulation of cell death pathways with co-delivered reagents promotes PDT induced tumor cell death. Relief of tumor resistance to PDT with combined therapy strategies further promotes tumor inhibition. Also, the optimization of photosensitizer formulations and therapy procedures reduces pain in PDT. Here, a systematic summary of recent advances in the fabrication of photosensitizers and the design of therapy strategies to overcome barriers in PDT is presented. Several aspects important for the clinical application of PDT in cancer treatment are also discussed.

Anticancer Photodynamic Therapy Properties of Sulfur-Doped Graphene Quantum Dot and Methylene Blue Preparations in MCF-7 Breast Cancer Cell Culture

Photodynamic therapy (PDT) is a field with many applications including chemotherapy. Graphene quantum dots (GQDs) exhibit a variety of unique properties and can be used in PDT to generate singlet oxygen that destroys pathogenic bacteria and cancer cells. The PDT agent, methylene blue (MB), like GQDs, has been successfully exploited to destroy bacteria and cancer cells by increasing reactive oxygen species generation. Recently, combinations of GQDs and MB have been shown to destroy pathogenic bacteria via increased singlet oxygen generation. Here, we performed a spectrophotometric assay to detect and measure the uptake of GQDs, MB and several GQD-MB combinations in MCF-7 breast cancer cells. Then, we used a cell counting method to evaluate the cytotoxicity of GQDs, MB and a 1:1 GQD:MB preparation. Singlet oxygen generation in cells was then detected and measured using singlet oxygen sensor green. The dye, H₂ DCFDA, was used to measure reactive oxygen species production. We found that GQD and MB uptake into MCF-7 cells occurred, but that MB, followed by 1:1 GQD:MB, caused superior cytotoxicity and singlet oxygen and reactive oxygen species generation. Our results suggest that methylene blue's effect against MCF-7 cells is not potentiated by GQDs, either in light or dark conditions.

A chemiluminescence biosensor for the detection of thrombin based on the aptamer composites

An efficient, rapid, simple and ultrasensitive chemiluminescence (CL) approach was proposed for thrombin detection based on the aptamer-thrombin recognition. The aptamer composites were synthesized in this work using graphene oxide (GO) as the backing material. The thrombin was adsorbed on the aptamer composites based on the aptamer-thrombin recognition. Thus, thrombin could be quantified by the difference value of the CL intensity between supernate of the sample and the mixture which composed of thrombin and coexisted substances. The CL intensity exhibits a stable response to thrombin over a concentration range from 2.5×10^-10 to 1×10^-9mol·L^-1 with a detection limit as low as 8.3×10^-11mol·L^-1, the relative standard deviation (RSD) was found to be 4.9% for 11 determinations of 1.25×10^-9mol·L^-1 thrombin. Finally, the applicability of the method was verified by applying to serum samples. The recoveries were in the range of 90.3-101.0% with RSD of 2.6-3.2%.

Anti-MUC1 aptamer: A potential opportunity for cancer treatment

Mucin 1 (MUC1) is a protein usually found on the apical surface of most normal secretory epithelial cells. However, in most adenocarcinomas, MUC1 is overexpressed, so that it not only appears over the entire cell surface, but is also shed as MUC1 fragments into the blood stream. These phenomena pinpoint MUC1 as a potential target for the diagnosis and treatment of cancer; consequently, interest has increased in MUC1 as a molecular target for overcoming cancer therapy challenges. MUC1 currently ranks second among 75 antigen candidates for cancer vaccines, and different antibodies or aptamers against MUC1 protein are proving useful for tracing cancer cells in the emerging field of targeted delivery. The unique properties of MUC1 aptamers as novel targeting agents, and the revolutionary role that MUC1 now plays in cancer therapy, are the focus of this review. Recent advancements in MUC1-targeted cancer therapy are also assessed.

Complexing Methylene Blue with Phosphorus Dendrimers to Increase Photodynamic Activity

The efficiency of photodynamic therapy is limited mainly due to low selectivity, unfavorable biodistribution of photosensitizers, and long-lasting skin sensitivity to light. However, drug delivery systems based on nanoparticles may overcome the limitations mentioned above. Among others, dendrimers are particularly attractive as carriers, because of their globular architecture and high loading capacity. The goal of the study was to check whether an anionic phosphorus dendrimer is suitable as a carrier of a photosensitizer-methylene blue (MB). As a biological model, basal cell carcinoma cell lines were used. We checked the influence of the MB complexation on its singlet oxygen production ability using a commercial fluorescence probe. Next, cellular uptake, phototoxicity, reactive oxygen species (ROS) generation, and cell death were investigated. The MB-anionic dendrimer complex (MB-1an) was found to generate less singlet oxygen; however, the complex showed higher cellular uptake and phototoxicity against basal cell carcinoma cell lines, which was accompanied with enhanced ROS production. Owing to the obtained results, we conclude that the photodynamic activity of MB complexed with an anionic dendrimer is higher than free MB against basal cell carcinoma cell lines.

Novel folic acid conjugated Fe3O4-ZnO hybrid nanoparticles for targeted photodynamic therapy

A novel folic acid conjugated core-shell hybrid iron oxide-zinc oxide nanoparticle was developed for applications as a photosensitier (PS) in photodynamic therapy. Photodegradation studies on methylene blue demonstrated significantly enhanced photophysical properties of the produced nano-PSs, due to the charge recombination via electron trapping by dissolved Fe³⁺. A time and dose dependant toxicity associated with the nano-PSs was observed upon exposure to human epithelial colorectal adenocarcinoma (Caco-2) cells in the dark. UV irradiation of the synthesised nano-PSs resulted in a significant photo-killing effect with drastic reduction in Caco-2 cell viability to as low as 6%. Reduction in viability upon exposure was due fundamentally to cellular interactions with light irradiated PSs as the influence of radiation alone was subtracted. FA conjugation further enhanced the photo-killing effect.

Materials for selective photo-oxygenation vs. photocatalysis: preparation, properties and applications in environmental and health fields

Photosensitizing materials made of organic dyes embedded in various supports are compared to usual supported TiO₂-based photocatalysts.