Studies of silica-hybrid nanoparticles with targeting and photodynamic capabilities for the topical therapy of melanoma

The topical treatment of skin cancer is a better alternative to systemic therapy. This is because of the accessibility of the cancerous tissue compared to deeper tissues. However, when it comes to melanoma, the topical treatment in clinics has been restricted by the limited penetration of drugs through the skin to the melanoma site. Of the possible modes of topical treatment, photodynamic therapy is the most promising, as it offers the added advantage of selectivity of therapy. However, for melanoma, photodynamic therapy is not yet used in clinics as the approved photosensitizers are unable to permeate deep enough into the skin, and the light wavelength used to activate them is not penetrative enough to reach the melanoma site. Furthermore, the photosensitizers that can absorb at longer wavelengths tend to be strongly hydrophobic and of high molecular weight, resulting in an inability to penetrate the skin barrier. Selectivity can be further improved by adding targeting ability to the particles. For melanoma, two small molecular inhibitors, Dabrafenib and Trametinib, have been identified as targeting chemotherapeutic drugs. These very promising inhibitors, however, suffer from several drawbacks, including their low bioavailability when systemically administered. A topical approach to deliver these inhibitors would be beneficial. In order to solve the problems faced in the topical treatment of melanoma using photodynamic therapy and targeted therapy, this work explored the use of nanotechnology, in particular a class of materials called organic-inorganic hybrid mesoporous nanoparticles. This class of nanomaterials are an extension of the conventional mesoporous silica nanoparticles, in which the silica skeleton of the nanoparticle can be modified organically, giving the nanoparticle functional xiii abilities while freeing up the mesopores for additional drug loading. Such particles have not been explored for topical therapy previously. The synthesis procedure and chemicals required were first optimised. Variables such as the TMOS to PC ratio and the inhibitor ratio were studied in terms of photodynamic efficiency, and optimized. Following which, the nanoparticle was characterised in depth using various techniques. It was shown to have a good singlet oxygen quantum yield of 0.42 and excellent photostability. Its small size and surface area enables more interaction of the generated ROS with intracellular biomolecules, improving overall efficacy of photodynamic therapy, and also the permeation through skin. The final product (PcNP@Drug) was first tested in vitro against the melanoma cell lines (BRAFV600E, BRAFwt) and healthy skin cells. It was effective against BRAFV600E cells, proving its efficacy and specificity towards the targeted BRAFV600E cells, while not affecting the healthy or BRAFwt cells as much. The combination analysis was also conducted, and it was observed that photodynamic therapy and the two inhibitors worked synergistically together for the BRAFV600E mutant cells. Various assays such as live/dead, in vitro ROS generation assays were also conducted and it was shown that ROS can be generated in cells as well, and the cells could die. Subsequently, the penetration ability of PcNP@Drug was tested on full-thickness porcine skin and was observed that with the use of microneedles, the penetration was much higher than without.. The microneedle approach to topical administration has the benefit of reducing drug build-up in the epidermis, and thus minimize damage to healthy cells. The PcNP@Drug nanoplatform was then xiv tested on living mice and it was proven that the nanosystem was able to not only permeate through into the melanoma subcutaneous growths, but the combined targeted therapy and photodynamic therapy was able to inhibit tumour growth. The results obtained in this study show that this PcNP@Drug nanosystem can be used as a topical method for treating the deeper-seated malignancies in skin, with reduced damage to healthy cells, especially in conjunction with the microneedle approach.Doctor of Philosoph

Environment‐adaptive coassembly/self‐sorting and stimulus‐responsiveness transfer based on cholesterol building blocks

Manipulating the property transfer in nanosystems is a challenging task since it requires switchable molecular packing such as separate aggregation (self‐sorting) or synergistic aggregation (coassembly). Herein, a unique manipulation of self‐sorting/coassembly aggregation and the observation of switchable stimulus‐responsiveness transfer in a two component self‐assembly system are reported. Two building blocks bearing the same cholesterol group give versatile topological structures in polar and nonpolar solvents. One building block (cholesterol conjugated cynanostilbene, CCS) consists of cholesterol conjugated with a cynanostilbene unit, and the other one (C10CN) is comprised of cholesterol connected with a naphthalimide group having a flexible long alkyl chain. Their assemblies including gel, crystalline plates, and vesicles are obtained. In gel and crystalline plate phases, the self‐sorting behavior dominates, while synergistic coassembly occurs in vesicle phase. Since CCS having the cyanostilbene group can respond to the light irradiation, it undergoes light‐induced chiral amplification. C10CN is thermally responsive, whereby its supramolecular chirality is inversed upon heating. In coassembled vesicles, it is interestingly observed that their responsiveness can be transferred by each other, i.e., the C10CN segment is sensitive to the light irradiation, while CCS is thermoresponsive. This unprecedented behavior of the property transfer may shine a light to the precise fabrication of smart materials.Published versio

NIR-light-activated combination therapy with a precise ratio of photosensitizer and prodrug using a host-guest strategy

The co-delivery of photosensitizers with prodrugs sensitive to reactive oxygen species (ROS) for light-triggered ROS generation and cascaded prodrug activation has drawn tremendous attention. However, the absence of a feasible method to deliver the two components at a precise ratio has impaired the application potential. Herein, we report an efficient method to produce a nanosized platform for the delivery of an optimized ratio of the two components by the means of host–guest strategy for maximizing the combination therapy efficacy of cancer treatment. The key features of this host–guest strategy for the combination therapy are that the ratio between photosensitizer and ROS-sensitive prodrug can be easily tuned, near-infrared (NIR) irradiation can sensitize the photosensitizer and activate the paclitaxel prodrug for its release, and the accumulation process can be tracked by NIR imaging to maximize the efficacy of photodynamic and chemotherapy.NRF (Natl Research Foundation, S’pore)ASTAR (Agency for Sci., Tech. and Research, S’pore)MOE (Min. of Education, S’pore)Accepted versio

Cu_2–<i>x</i>S Nanocrystals Cross-Linked with Chlorin e6-Functionalized Polyethylenimine for Synergistic Photodynamic and Photothermal Therapy of Cancer

Achieving an integrated system for combinational therapy of cancer with enhanced efficacy is always a challenge. A multifunctional system (CCeT nanoparticles (NPs)) for a synergistic photodynamic and photothermal cancer therapy was successfully developed. This system is composed of Cu_2–<i>x</i>S nanoclusters functionalized with chlorin e6 (Ce6)-conjugated branched polyethylenimine (PEI-Ce6) and mitochondria-targeting 3-(carboxypropyl)­triphenylphosphonium bromide (TPP-COOH). The colocalization of the resulted CCeT NPs inside the mitochondria of cancer cells was proven. The CCeT NPs exhibited significant photodynamic therapy (PDT) efficacy due to efficient singlet oxygen (¹O₂) generation triggered by a 630 nm laser. This system also showed excellent photothermal conversion capability upon the irradiation of 808 nm laser for photothermal therapy (PTT). In particular, the platform achieved nearly 100% inhibitory rate of the tumor growth in vivo through combinational PDT and PTT. Thus, the CCeT NPs could efficiently inhibit the tumor growth in vitro and in vivo by combinational PDT and PTT, offering synergistic therapeutic efficiency as compared to PTT or PDT alone

Microneedle-assisted topical delivery of photodynamically active mesoporous formulation for combination therapy of deep-seated melanoma

Topical treatment using photodynamic therapy (PDT) for many types of skin cancers has largely been limited by the inability of existing photosensitizers to penetrate into the deep skin tissue. To overcome these problems, we developed a mesoporous nanovehicle with dual loading of photosensitizers and clinically relevant drugs for combination therapy, while utilizing microneedle technology to facilitate their penetration into deep skin tissue. Sub-50 nm photodynamically active mesoporous organosilica nanoparticles were synthesized with photosensitizers covalently bonded to the silica matrix, which dramatically increased the quantum yield and photostability of these photosensitizers. The mesopores of the nanoparticles were further loaded with small-molecule inhibitors, i. e., dabrafenib and trametinib, that target the hyperactive mitogen-activated protein kinase (MAPK) pathway for melanoma treatment. As-prepared empty nanovehicle was cytocompatible with normal skin cells in the dark, while NIR-irradiated drug-loaded nanovehicle showed a synergistic killing effect on skin cancer cells mainly through reactive oxygen species and caspase-activated apoptosis. The nanovehicle could significantly inhibit the proliferation of tumor cells in a 3D spheroid model in vitro. Porcine skin fluorescence imaging demonstrated that microneedles could facilitate the penetration of nanovehicle across the epidermis layer of skin to reach deep-seated melanoma sites. Tumor regression studies in a xenografted melanoma mouse model confirmed superior therapeutic efficacy of the nanovehicle through combinational PDT and targeted therapy.Nanyang Technological UniversityNational Research Foundation (NRF)This research is supported by the Singapore National Research Foundation Investigatorship (NRF-NRFI2018-03) and the NTU-Northwestern Institute for Nanomedicine

MTH1 inhibitor amplifies the lethality of reactive oxygen species to tumor in photodynamic therapy

Although photodynamic therapy (PDT) has been clinically applied tumor hypoxia still greatly restricts the performance of this oxygen-dependent oncological treatment. The delivery of oxygen donors to tumor may produce excessive reactive oxygen species (ROS) and damage the peripheral tissues. Herein, we developed a strategy to solve the hypoxia issue by enhancing the lethality of ROS. Before PDT, the ROS-defensing system of the cancer cells was obstructed by an inhibitor to MTH1, which is a key for the remediation of ROS-caused DNA damage. As a result, both nuclei and mitochondrial DNA damages were increased, remarkably promoting cellular apoptosis. The therapeutic results demonstrated that the performance of PDT can be improved by the MTH1 inhibitor, leading to efficient cancer cell killing effect in the hypoxic tumor. This strategy makes better use of the limited oxygen, holding the promise to achieve satisfactory therapeutic effect by PDT without generating redundant cytotoxic ROS.Agency for Science, Technology and Research (A*STAR)National Research Foundation (NRF)Published versionThis research is supported by the Singapore National Research Foundation Investigatorship (NRF-NRFI2018-03) and the Singapore Agency for Science, Technology and Research (A*STAR) AME IRG grant (A1883c0005). This work is also supported by the National Science Foundation of China (81702998 and 81701766)

Combined Photodynamic and Photothermal Therapy Using Cross-Linked Polyphosphazene Nanospheres Decorated with Gold Nanoparticles

A rational combination of photodynamic therapy (PDT) and photothermal therapy (PTT) could achieve a synergistic therapeutic effect to enhance therapeutic efficacy in the cancer treatment. Herein, polyphosphazene nanospheres as a novel kind of photosensitizer carriers were synthesized by anchoring and isolating photosensitizing porphyrin monomers covalently in the cross-linked structure. Gold nanoparticles were then immobilized on the surface of the nanospheres to introduce the photothermal performance. The hybrid system was eventually conjugated by polyethylene glycol to decrease its cytotoxicity. The morphology analysis showed that the nanospheres were covered by homogeneously dispersed gold nanoparticles. In this way, the resulted system could afford efficient photodynamic and photothermal effect simultaneously, as confirmed by the cancer cell killing studies. The cell experiments demonstrated that the as-prepared polyphosphazene nanospheres with inherent fluorescence could be internalized by HeLa cells, showing high performance of combined PDT and PTT under suitable light irradiation. Thus, this integrated system presents its effectiveness to achieve combined PDT and PTT for enhanced cancer therapeutics

Independent of EPR effect : a smart delivery nanosystem for tracking and treatment of nonvascularized intra-abdominal metastases

Nanoparticle-based delivery systems (NDS) have impacted the field of cancer therapy on account of the enhanced permeability and retention (EPR) effect that promotes passive accumulation in tumors through the tumor vasculature after intravenous (IV) administration. However, transplanted tumor xenografts on animal models used to justify the feasibility of EPR effect are quite different from clinical tumors in many aspects, a fact that becomes an impediment for NDS to succeed clinical trials. Particularly, early-stage tumor metastases are usually nonvascularized and incapable of conforming the EPR effect after IV injection. Therefore, it is necessary to develop smart NDS to deliver drugs in an EPR-independent route. Herein, an NDS-based treatment approach for intra-abdominal metastases from ovarian carcinoma is reported. Instead of IV injection, intraperitoneal (IP) injection was employed to directly apply the NDS to the metastatic lesions. The NDS was tailor-made with targeting groups to actively target the tumor nidus and redox-responsive drug release to reduce systematic toxicity. Comparing with IV administration, the IP injected NDS could be enriched in metastatic tumor more efficiently, leading to superior therapeutic outcome in vivo. This study provides a successful protocol of EPR independent NDS-based cancer treatment, which may facilitate the clinical translation of nanoparticle-based cancer therapeutics.NRF (Natl Research Foundation, S’pore)Accepted versio