Light-Activatable Red Blood Cell Membrane-Camouflaged Dimeric Prodrug Nanoparticles for Synergistic Photodynamic/Chemotherapy

Recent Advances in Cell Membrane-Camouflaged Nanoparticles for Cancer Phototherapy

Phototherapy including photothermal therapy (PTT) and photodynamic therapy (PDT) employs phototherapeutic agents to generate heat or cytotoxic reactive oxygen species (ROS), and has therefore garnered particular interest for cancer therapy. However, the main challenges faced by conventional phototherapeutic agents include easy recognition by the immune system, rapid clearance from blood circulation, and low accumulation in target sites. Cell-membrane coating has emerged as a potential way to overcome these limitations, owing to the abundant proteins on the surface of cell membranes that can be inherited to the cell membrane-camouflaged nanoparticles. This review summarizes the recent advances in the development of biomimetic cell membrane-camouflaged nanoparticles for cancer phototherapy. Different sources of cell membranes can be used to coat nanoparticles uisng different coating approaches. After cell-membrane coating, the photophysical properties of the original phototherapeutic nanoparticles remain nearly unchanged; however, the coated nanoparticles are equipped with additional physiological features including immune escape, in vivo prolonged circulation time, or homologous targeting, depending on the cell sources. Moreover, the coated cell membrane can be ablated from phototherapeutic nanoparticles under laser irradiation, leading to drug release and thus synergetic therapy. By combining other supplementary agents to normalize tumor microenvironment, cell-membrane coating can further enhance the therapeutic efficacy against cancer.

A New Era of Cardiac Cell Therapy: Opportunities and Challenges

Myocardial infarction (MI), caused by coronary heart disease (CHD), remains one of the most common causes of death in the United States. Over the last few decades, scientists have invested considerable resources on the study and development of cell therapies for myocardial regeneration after MI. However, due to a number of limitations, they are not yet readily available for clinical applications. Mounting evidence supports the theory that paracrine products are the main contributors to the regenerative effects attributed to these cell therapies. The next generation of cell-based MI therapies will identify and isolate cell products and derivatives, integrate them with biocompatible materials and technologies, and use them for the regeneration of damaged myocardial tissue. This review discusses the progress made thus far in pursuit of this new generation of cell therapies. Their fundamental regenerative mechanisms, their potential to combine with other therapeutic products, and their role in shaping new clinical approaches for heart tissue engineering, are addressed.

Self-destructive PEG–BODIPY nanomaterials for photodynamic and photothermal therapy

Amphiphilic photosensitizers are made from boron dipyrromethene and poly(ethylene glycol) by using a thioketal linker, which is reactive oxygen species-responsive for photodynamic and photothermal therapy.

Polydopamine-modified ROS-responsive prodrug nanoplatform with enhanced stability for precise treatment of breast cancer

Development of smart stimuli-responsive prodrug nanomaterials for fast drug release and efficient antitumor therapy has attracted great attention in recent years. However, the inherent instability of naked prodrugs in the blood is an important challenge limiting their biomedical applications. Although a number of strategies have been taken to prevent prodrugs from hydrolyzing due to blood composition, most of these strategies are unsatisfactory. Here, we designed an extraordinary ROS-triggered prodrug nanoplatform fabricated by using a single thioether linker to conjugate PTX with 6-maleimidocaproic acid (MAL), resulting in the PTX-S-MAL prodrug self-assembling into uniform size nanoparticles; then the prodrug nanoplatform was modified with a polydopamine coating and PEGylation to confer high solubility and stability. In in vitro experiments, the polydopamine-modified ROS-responsive prodrug nanosystem showed a high sensitivity in term of various H₂O₂ concentrations, and the PDA coating on the surface of the prodrug nanosystem didn't affect the drug release properties. Moreover, the excellent polydopamine-modified ROS-triggered prodrug nanoplatform selectively and rapidly releases PTX in response to the ROS overproduced in tumor cells, but showed less cytotoxicity against normal cells. In in vivo experiments, the prepared polydopamine-modified prodrug-nanosystem obviously enhances the stability and tumor accumulation of prodrug, producing a remarkably improved breast cancer treatment with minimal side effects. Our studies demonstrated that this modified nanoplatform could significantly improve chemotherapy efficiency, which will find great potential in cancer treatment.

Development of smart stimuli-responsive prodrug nanomaterials for fast drug release and efficient antitumor therapy has attracted great attention in recent years.

ROS-sensitive biomimetic nanocarriers modulate tumor hypoxia for synergistic photodynamic chemotherapy

The biomimetic NPs@i-RBM have the potential to overcome hypoxia-limited PDT, and significantly improve the anticancer efficacy by synergistic PDT and hypoxia-activated chemotherapy.

Light-responsive nanomedicine for biophotonic imaging and targeted therapy

Nanoparticles (NPs) play a key role in nanomedicine in multimodal imaging, drug delivery and targeted therapy of human diseases. Consequently, due to the attractive properties of NPs including high stability, high payload, multifunctionality, design flexibility, and efficient delivery to target tissues, nanomedicine employs various types of NPs to enhance targeting and treatment efficacy. In this review, we primarily focus on light-responsive materials, such as fluorophores, photosensitizers, semiconducting polymers, carbon structures, gold particles, quantum dots, and upconversion crystals, for their biomedical applications. Armed with these nanomaterials, NPs represent a growing potential in biophotonic imaging (luminescence, photoacoustic, surface enhanced Raman scattering, and optical coherence tomography) as well as targeted therapy (photodynamic therapy, photothermal therapy, and light-responsive drug release).

A polymer-free, biomimicry drug self-delivery system fabricated via a synergistic combination of bottom-up and top-down approaches

Compared to conventional carrier-assistant drug delivery systems (DDSs), drug self-delivery systems (DSDSs) have advantages of unprecedented drug loading capacity, minimized carrier-related toxicity and ease of preparation. However, the colloidal stability and blood circulation time of DSDSs still need to be improved. Here we report on the development of a novel biomimicry drug self-delivery system by the integration of a top-down cell membrane complexing technique into our self-delivery multifunctional nano-platform made from bottom-up approach that contains 100% active pharmaceutical ingredients (API) of Pheophorbide A and Irinotecan conjugates (named PI). Compared to conventional cell membrane coated nanoparticles with polymer framework as core and relatively low drug loading, this system consisting of red blood cell membrane vesicles complexed PI (RBC-PI) is polymer-free with up to 50% API loading. RBC-PI exhibited 10 times higher area under curve in pharmacokinetic study and much lower macrophage uptake compared with the parent PI nanoparticles. RBC-PI retained the excellent chemophototherapeutic effects of the PI nanoparticles, but possessed superior anti-cancer efficacy with prolonged blood circulation, improved tumor delivery, and enhanced photothermal effects in animal models. This system represents a novel example of using cell membrane complexing technique for effective surface modification of DSDSs. This is also an innovative study to form a polymer-free cell membrane nanoparticle complexing with positive surface charged materials. This biomimicry DSDS takes advantages of the best features from both systems to make up for each other's shortcomings and posed all the critical features for an ideal drug delivery system.

Functional Polymer Nanocarriers for Photodynamic Therapy

Photodynamic therapy (PDT) is an appealing therapeutic modality in management of some solid tumors and other diseases for its minimal invasion and non-systemic toxicity. However, the hydrophobicity and non-selectivity of the photosensitizers, inherent serious hypoxia of tumor tissues and limited penetration depth of light restrict PDT further applications in clinic. Functional polymer nanoparticles can be used as a nanocarrier for accurate PDT. Here, we elucidate the mechanism and application of PDT in cancer treatments, and then review some strategies to administer the biodistribution and activation of photosensitizers (PSs) to ameliorate or utilize the tumor hypoxic microenvironment to enhance the photodynamic therapy effect.

A high therapeutic efficacy of polymeric prodrug nano-assembly for a combination of photodynamic therapy and chemotherapy

Combination of photodynamic therapy and chemotherapy has been emerging as a new strategy for cancer treatment. Conventional photosensitizer tends to aggregate in aqueous media, which causes fluorescence quenching, reduces reactive oxygen species (ROS) production, and limits its clinical application to photodynamic therapy. Traditional nanoparticle drug delivery system for chemotherapy also has its disadvantages, such as low drug loading content, drug leakage, and off-target toxicity for normal tissues. Here, we developed a reduction-sensitive co-delivery micelles TB@PMP for combinational therapy, which composed of entrapping a red aggregation-induced emission fluorogen (AIEgen) for photodynamic therapy and PMP that contains a reduction-sensitive paclitaxel polymeric prodrug for chemotherapy. AIEgen photosensitizer illustrates a much improved photostability and ROS production efficiency in aggregate state and PMP loads a high dose of paclitaxel and carries a smart stimuli-triggered drug release property. This co-delivery system provides a better option that replaces AIEgen photosensitizer for cancer diagnosis and therapy.

Xiaoqing Yi et al. report a co-drug delivery micelle system that demonstrates a high therapeutic efficacy for cancer. This system shows a much improved drug load, photostability, and production of reactive oxygen species, compared to traditional photosensitizer-loaded nanoparticles.

Prospects and Challenges of Phospholipid-Based Prodrugs

Nowadays, the prodrug approach is used already at the early stages of drug development. Lipidic prodrug approach is a growing field for improving a number of drug properties/delivery/therapy aspects, and can offer solutions for various unmet needs. This approach includes drug moiety bound to the lipid carrier, which can be triglyceride, fatty acids, steroid, or phospholipid (PL). The focus of this article is PL-based prodrugs, which includes a PL carrier covalently bound to the active drug moiety. An overview of relevant physiological lipid processing pathways and absorption barriers is provided, followed by drug delivery/therapeutic application of PL-drug conjugates, as well as computational modeling techniques, and a modern bioinformatics tool that can aid in the optimization of PL conjugates. PL-based prodrugs have increased lipophilicity comparing to the parent drug, and can therefore significantly improve the pharmacokinetic profile and overall bioavailability of the parent drug, join the endogenous lipid processing pathways and therefore accomplish drug targeting, e.g., by lymphatic transport, drug release at specific target site(s), or passing the blood-brain barrier. Moreover, an exciting gateway for treating inflammatory diseases and cancer is presented, by utilizing the PL sn-2 position in the prodrug design, aiming for PLA₂-mediated activation. Overall, a PL-based prodrug approach shows great potential in improving different drug delivery/therapy aspects, and is expected to grow.

Erythrocyte Membrane Cloaked Metal-Organic Framework Nanoparticle as Biomimetic Nanoreactor for Starvation-Activated Colon Cancer Therapy

Shutting down glucose supply by glucose oxidase (GOx) to starve tumors has been considered to be an attractive strategy in cancerous starvation therapy. Nevertheless, the in vivo applications of GOx-based starvation therapy are severely restricted by the poor GOx delivery efficiency and the self-limiting therapeutic effect. Herein, a biomimetic nanoreactor has been fabricated for starvation-activated cancer therapy by encapsulating GOx and prodrug tirapazamine (TPZ) in an erythrocyte membrane cloaked metal-organic framework (MOF) nanoparticle (TGZ@eM). The fabricated TGZ@eM nanoreactor can assist the delivery of GOx to tumor cells and then exhaust endogenous glucose and O₂ to starve tumors efficiently. Importantly, the resulting tumor hypoxia by GOx-based starvation therapy further initiates the activation of TPZ, which is released from the nanoreactor in the acid lyso/endosome environment, for enhanced colon cancer therapy. More importantly, by integrating the biomimetic surface modification, the immunity-escaping and prolonged blood circulation characteristics endow our nanoreactor dramatically improved cancer targeting ability. The in vitro and in vivo outcomes indicate our biomimetic nanoreactor exhibits a strong synergistic cascade effect for colon cancer therapy in an accurate and facile manner.

Targeting myeloid regulators by paclitaxel-loaded enzymatically degradable nanocups

Tumor microenvironment is characterized by immunosuppressive mechanisms associated with the accumulation of immune regulatory cells - myeloid-derived suppressor cells (MDSC). Therapeutic depletion of MDSC has been associated with inhibition of tumor growth and therefore represents an attractive approach to cancer immunotherapy. MDSC in cancer are characterized by enhanced enzymatic capacity to generate reactive oxygen and nitrogen species (RONS) which have been shown to effectively degrade carbonaceous materials. We prepared enzymatically openable nitrogen-doped carbon nanotube cups (NCNC) corked with gold nanoparticles and loaded with paclitaxel as a therapeutic cargo. Loading and release of paclitaxel was confirmed through electron microscopy, Raman spectroscopy and LC-MS analysis. Under the assumption that RONS generated by MDSCs can be utilized as a dual targeting and oxidative degradation mechanism for NCNC, here we report that systemic administration of paclitaxel loaded NCNC delivers paclitaxel to circulating and lymphoid tissue MDSC resulting in the inhibition of growth of tumors (B16 melanoma cells inoculated into C57BL/6 mice) in vivo. Tumor growth inhibition was associated with decreased MDSC accumulation quantified by flow cytometry that correlated with bio-distribution of gold-corked NCNC resolved by ICP-MS detection of residual gold in mouse tissue. Thus, we developed a novel immunotherapeutic approach based on unique nanodelivery vehicles, which can be loaded with therapeutic agents that are released specifically in MDSC via NCNC selective enzymatic "opening" affecting change in the tumor microenvironment.

Cell Membrane-Camouflaged Nanoparticles: A Promising Biomimetic Strategy for Cancer Theragnostics

Biomimetic functionalization of nanoparticles through camouflaging with cellular membranes has emerged as a promising strategy for cancer theragnostics. Cellular membranes used for camouflaging nanoparticles are generally isolated from blood cells, immune cells, cancer cells, and stem cells. The camouflaging strategy of wrapping nanoparticles with cellular membranes allows for superior tumor targeting through self-recognition, homotypic targeting and prolonged systematic circulation, thereby aiding in effective tumor therapy. In this review, we emphasized the various types of cellular membrane-camouflaged nanoparticles, their mechanisms in targeted therapy and various biomimetic strategies for anti-cancer therapy.

Photoresponsive Drug/Gene Delivery Systems

Light as an external stimulus can be precisely manipulated in terms of irradiation time, site, wavelength, and density. As such, photoresponsive drug/gene delivery systems have been increasingly pursued and utilized for the spatiotemporal control of drug/gene delivery to enhance their therapeutic efficacy and safety. In this review, we summarized the recent research progress on photoresponsive drug/gene delivery, and two major categories of delivery systems were discussed. The first category is the direct responsive systems that experience photoreactions on the vehicle or drug themselves, and different materials as well as chemical structures responsive to UV, visible, and NIR light are summarized. The second category is the indirect responsive systems that require a light-generated mediator signal, such as heat, ROS, hypoxia, and gas molecules, to cascadingly trigger the structural transformation. The future outlook and challenges are also discussed at the end.

Hierarchical nanocomposites of graphene oxide and PEGylated protoporphyrin as carriers to load doxorubicin hydrochloride for trimodal synergistic therapy

We report a supramolecular hierarchical nanocomposite for combination photodynamic, photothermal, and chemotherapy.

Reprogramming axial ligands facilitates the self-assembly of a platinum(iv) prodrug: overcoming drug resistance and safer in vivo delivery of cisplatin

We herein reprogrammed axial ligands of platinum(iv) prodrugs, conferring the constructed prodrug entities with the ability to self-assemble in aqueous solution.