Real-Time Visualization of Lysosome Destruction Using a Photosensitive Toluidine Blue Nanogel

Hijacking the hyaluronan assisted iron endocytosis to promote the ferroptosis in anticancer photodynamic therapy

Photodynamic therapy (PDT) eradicates tumor cells by the light-stimulated reactive oxygen species, which also induces lipid peroxidation (LPO) and subsequently ferroptosis, an iron-depended cell death. Ferroptosis has a tremendous therapeutic potential in cancer treatment, however, the ferroptosis efficiency is largely limited by the available iron in cells. Through hijacking the CD44-mediated iron endocytosis of hyaluronan (HA), here PDT with enhanced ferroptosis was realized by a HA@Ce6 nanogel self-assembled from HA, a photosensitizer Chlorin e6 (Ce6) and Fe3+ as cross-linkers. Taking advantages of HA's natural affinity towards CD44, HA@Ce6 enabled a targeted Ce6 delivery in CD44-overexpressed breast cancer cells and meanwhile enhanced iron uptake to "fuel" ferroptosis together with the light-stimulated LPO. Further, HA@Ce6 demonstrated an excellent anticancer PDT efficacy and ferroptosis induction in the murine 4 T1 xenograft model. This HA@Ce6 successfully exploited the role of HA in iron transport to sensitize ferroptosis, providing a potent strategy to facilitate the anticancer PDT.

Facile preparation of toluidine blue-loaded DNA nanogels for anticancer photodynamic therapy

Photodynamic therapy (PDT) provides an effective therapeutic option for different types of cancer in addition to surgery, radiation, and chemotherapy. The treatment outcome of PDT is largely determined by both the light and dark toxicity of photosensitizers (PSs), which can be technically improved with the assistance of a drug delivery system, especially the nanocarriers. Toluidine blue (TB) is a representative PS that demonstrates high PDT efficacy; however, its application is largely limited by the associated dark toxicity. Inspired by TB's noncovalent binding with nucleic acids, in this study, we demonstrated that DNA nanogel (NG) could serve as an effective TB delivery vehicle to facilitate anticancer PDT. The DNA/TB NG was constructed by the simple self-assembly between TB and short DNA segments using cisplatin as a crosslinker. Compared with TB alone, DNA/TB NG displayed a controlled TB-releasing behavior, effective cellular uptake, and phototoxicity while reducing the dark toxicity in breast cancer cells MCF-7. This DNA/TB NG represented a promising strategy to improve TB-mediated PDT for cancer treatments.

Developing a far-red fluorogenic beta-galactosidase probe for senescent cell imaging and photoablation

A methylene blue (MB)-based beta-galactosidase (β-gal) activatable molecule, Gal-MB, was developed for senescence imaging and light-triggered senolysis. When in contact with LacZ β-gal or senescence-associated β-gal (SA-β-gal), the photoinsensitive Gal-MB becomes fluorescent. Gal-MB also offered selective phototoxicity toward LacZ β-gal expressing cells and drug-induced senescent cells, which express SA-β-gal, after light illumination at 665 nm.

A methylene blue (MB)-based beta-galactosidase (β-gal) activatable molecule, Gal-MB, was developed for senescence imaging and light-triggered senolysis.

A Hybrid Nanogel to Preserve Lysosome Integrity for Fluorescence Imaging

Fluorescence imaging of lysosomes provides a powerful tool to probe the lysosome physiology in living cells, yet the continuous light exposure inevitably causes lysosome damage and phototoxicity, which remains a formidable challenge. Here the long-term lysosome tracking with minimized photodamage was realized using a multifunctional nanoprobe, a platinum nanoparticle, and a quinacrine co-loaded nanogel. To construct the hybrid nanogel, cisplatin first functioned as cross-linker to withhold all components and then was reduced to a platinum nanoparticle in situ by ethanol. The platinum nanoparticle enabled a long-term quinacrine fluorescence imaging of lysosome by scavenging the light induced reactive oxygen species which could damage lysosomal membranes.

TB@PLGA Nanoparticles for Photodynamic/Photothermal Combined Cancer Therapy with Single Near-Infrared Irradiation

Background

Phototherapy has significant potential as an effective treatment for cancer. However, the application of a multifunctional nanoplatform for photodynamic therapy (PDT) and photothermal therapy (PTT) at a single excitation wavelength remains a challenge.

Materials and Methods

The double emulsion solvent evaporation method was used to prepare toluidine blue@poly lactic-co-glycolic acid (TB@PLGA) nanoparticles (NPs). The biocompatibility of TB@PLGA NPs was evaluated, and a 660 nm luminescence was used as the light source. The photothermal effect, photothermal stability, and singlet oxygen yield of NPs in an aqueous solution verified the feasibility of NPs as a PTT/PDT synergistic therapy drug.

Results

TB@PLGA NPs were successfully prepared and characterized. In vitro experiments demonstrated that TB@PLGA NPs can cause massive necrosis of tumor cells and induce apoptosis through a photodynamic mechanism under 660 nm laser irradiation. The TB@PLGA NPs also achieved optimal tumor inhibition effect in vivo.

Conclusion

The TB@PLGA NPs prepared in this study were applied as a dual-mode phototherapeutic agent under single laser irradiation. Both in vitro and in vivo experiments demonstrated the good potential of PTT/PDT for tumor inhibitors.

Self-Assembled Nanogels Based on Ionic Gelation of Natural Polysaccharides for Drug Delivery

The polysaccharides (PS) have been widely used as biomaterials in drug delivery, due to their excellent biocompatibility, ease of functionalization, and intrinsic biological activities. Among the various PS-based biomaterials, the self-assembled PS nanogels (NG) featuring facile preparation are attracting evergrowing interests in various biomedical applications. Specifically, NG derived from the self-assembly of natural PS well maintain both the physicochemical and biological properties of PS while avoiding the chemical modification or alteration of PS structure, representing a potent drug delivery system for various therapeutic agents. In this review, the natural PS, such as chitosan, alginate, and hyaluronan, for self-assembled NG construction and their advantages in the applications of drug delivery have been summarized. The residues, such as amine, carboxyl, and hydroxyl groups, on these PS provide multiple sites for both ionic cross-linking and metal coordination, which greatly contribute to the formation of self-assembled NG as well as the drug loading, thus enabling a wide biomedical application of PS NG, especially for drug delivery. Future developments and considerations in the clinical translation of these self-assembled PS NG have also been discussed.

Hyaluronan-based Multifunctional Nano-carriers for Combination Cancer Therapy

Hyaluronan (HA) is a natural linear polysaccharide that has excellent hydrophilicity, biocompatibility, biodegradability, and low immunogenicity, making it one of the most attractive biopolymers used for biomedical researches and applications. Due to the multiple functional sites on HA and its intrinsic affinity for CD44, a receptor highly expressed on various cancer cells, HA has been widely engineered to construct different drug-loading nanoparticles (NPs) for CD44-targeted anti-tumor therapy. When a cocktail of drugs is co-loaded in HA NP, a multifunctional nano-carriers could be obtained, which features as a highly effective and self-targeting strategy to combat cancers with CD44 overexpression. The HA-based multidrug nano-carriers can be a combination of different drugs, various therapeutic modalities, or the integration of therapy and diagnostics (theranostics). Up to now, there are many types of HA-based multidrug nano-carriers constructed by different formulation strategies, including drug co-conjugates, micelles, nano-gels and hybrid NP of HA and so on. This multidrug nano-carrier takes the full advantages of HA as an NP matrix, drug carriers and targeting ligand, representing a simplified and biocompatible platform to realize the targeted and synergistic combination therapy against the cancers. In this review, recent progress of HA-based multidrug nano-carriers for combination cancer therapy is summarized and the potential challenges for translational applications have been discussed.

Lysosome-Targeted Gold Nanotheranostics for In Situ SERS Monitoring pH and Multimodal Imaging-Guided Phototherapy

The integration of surface-enhanced Raman spectrum (SERS) and fluorescence-photoacoustic multimodal imaging in near-infrared photothermal therapy is highly desirable for cancer theranostic. However, typically, gold nanotheranostics usually require an additional modification of fluorophores and complex design refinements. In this work, by integrating surface-modified cysteine-hydroxyl merocyanine (CyHMC) molecules onto AuNRs, a novel lysosome-targeted gold-based nanotheranostics AuNRs-CyHMC that combines the specificity of Raman spectrum, the speed of fluorescence imaging, and deep penetration of photoacoustic imaging was successfully fabricated. Interestingly, fluorescence and Raman signals in this AuNRs-CyHMC system do not interfere, but it has pH-sensitive Raman signals and self-fluorescence localization ability under different excitation wavelengths. Fluorescence co-localization experiments further confirmed the lysosome-targeting ability of AuNRs-CyHMC. Typically, the proposed nanotheranostics were capable of SERS monitoring pH changes in both phosphate-buffered saline and living cells. Meanwhile, in vitro and in vivo experiments revealed that AuNRs-CyHMC possessed excellent fluorescence-photoacoustic performance and could be used for multimodal imaging-guided photothermal therapy. Furthermore, our work implied that gold nanotheranostics can provide great potential for cancer diagnosis and treatment.

Selective photo-ablation of glioma cells using an enzyme activatable photosensitizer

An activatable photosensitizer based on methylene blue was developed and validated for its efficacy in the selective killing of γ-glutamyl transpeptidase expressing cells. The ¹O₂ deactivation via bond breakage, rapid in situ enzymatic photosensitivity conversion, long lysosomal retention, and nucleus relocation collectively contribute to its strong and selective photodynamic effects.

Natural Hydrogels Applied in Photodynamic Therapy

Natural hydrogels are three-dimensional (3D) water-retaining materials with a skeleton consisting of natural polymers, their derivatives or mixtures. Natural hydrogels can provide sustained or controlled drug release and possess some unique properties of natural polymers, such as biodegradability, biocompatibility and some additional functions, such as CD44 targeting of hyaluronic acid. Natural hydrogels can be used with photosensitizers (PSs) in photodynamic therapy (PDT) to increase the range of applications. In the current review, the pertinent design variables are discussed along with a description of the categories of natural hydrogels available for PDT.

The Arctic Cylindrocystis (Zygnematophyceae, Streptophyta) Green Algae are Genetically and Morphologically Diverse and Exhibit Effective Accumulation of Polyphosphate

The green algal genus Cylindrocystis is widespread in various types of environments, including extreme habitats. However, very little is known about its diversity, especially in polar regions. In the present study, we isolated seven new Cylindrocystis-like strains from terrestrial and freshwater habitats in Svalbard (High Arctic). We aimed to compare the new isolates on a molecular (rbcL and 18S rDNA), morphological (light and confocal laser scanning microscopy), and cytological (Raman microscopy) basis. Our results demonstrated that the Arctic Cylindrocystis were not of a monophyletic origin and that the studied strains clustered within two clades (tentatively named the soil and freshwater/glacier clades) and four separate lineages. Morphological data (cell size, shape, and chloroplast morphology) supported the presence of several distinct taxa among the new isolates. Moreover, the results showed that the Arctic Cylindrocystis strains were closely related to strains originating from the temperate zone, indicating high ecological versatility and successful long-distance dispersal of the genus. Large amounts of inorganic polyphosphate (polyP) grains were detected within the chloroplasts of the cultured Arctic Cylindrocystis strains, suggesting effective luxury uptake of phosphorus. Additionally, various intracellular structures were identified using Raman microscopy and cytochemical and fluorescent staining. This study represents the first attempt to combine molecular, morphological, ecological, and biogeographical data for Arctic Cylindrocystis. Our novel cytological observations partially explain the success of Cylindrocystis-like microalgae in polar regions.

A Multiresponsive Nanohybrid to Enhance the Lysosomal Delivery of Oxygen and Photosensitizers

Photodynamic therapy (PDT) is a promising cancer ablation method, but its efficiency is easily affected by several factors, such as the insufficient delivery of photosensitizers, low oxygen levels as well as long distance between singlet oxygen and intended organelles. A multifunctional nanohybrid, named MGAB, consisting of gelatin-coated manganese dioxide and albumin-coated gold nanoclusters, was designed to overcome these issues by improving chlorin e6 (Ce6) delivery and stimulating oxygen production in lysosomes. MGAB were quickly degraded in a high hydrogen peroxide, high protease activity, and low pH microenvironment, which is closely associated with tumor growth. The Ce6-loaded MGAB were picked up by tumor cells through endocytosis, degraded within the lysosomes, and released oxygen and photosensitizers. Upon near-infrared light irradiation, the close proximity of oxygen with photosensitizer within lysosomes enabled the production of cytotoxic singlet oxygen, resulting in more effective PDT.