Hypoxia-sensitive drug delivery to tumors

Tumor Microenvironment-Responsive Polymer Delivery Platforms for Cancer Therapy

Most chemotherapeutic and bioimaging agents struggle with inadequate bioavailability, primarily due to their limited biocompatibility and lack of specificity in targeting, leading to low or decreased anticancer efficacy and inaccurate imaging. To surmount these obstacles, the development of stimuli-responsive polymer delivery platforms, predominantly leveraging the tumor microenvironment (TME), has emerged as a promising strategy. Therapeutic and diagnostic agents can be released controllably at the tumor site by virtue of the bond cleavage or hydrophobic to hydrophilic transformation of TME-sensitive linkages in TME-responsive systems, thus augmenting cancer treatment and imaging precision, while simultaneously attenuating the damage to healthy tissues and false imaging signals caused by non-specific drug leakage. In this comprehensive review, we scrutinize recent studies of TME-responsive polymer delivery platforms, encompassing pH-, ROS-, GSH-, enzyme-, and hypoxia-responsive vectors, significantly from the perspective of their molecular design and responsive mechanism, and further summarizing their bio-application in drug delivery and diagnostic imaging. Moreover, this review encapsulates the critical challenges and offers an insightful perspective on the future prospects of TME-responsive polymer delivery platforms in terms of molecular and vector design.

Development of Stimuli-Responsive Polymeric Nanomedicines in Hypoxic Tumors and Their Therapeutic Promise in Oral Cancer

Hypoxic tumors pose considerable obstacles to cancer treatment, as diminished oxygen levels can impair drug effectiveness and heighten therapeutic resistance. Oral cancer, a prevalent malignancy, encounters specific challenges owing to its intricate anatomical structure and the technical difficulties in achieving complete resection, thereby often restricting treatment efficacy. The impact of hypoxia is particularly critical in influencing both the treatment response and prognosis of oral cancers. This article summarizes and examines the potential of polymer nanomedicines to address these challenges. By engineering nanomedicines that specifically react to the hypoxic tumor microenvironment, these pharmaceuticals can markedly enhance targeting precision and therapeutic effectiveness. Polymer nanomedicines enhance therapeutic efficacy while reducing side effects by hypoxia-targeted accumulation. The article emphasizes that these nanomedicines can overcome the drug resistance frequently observed in hypoxic tumors by improving the delivery and bioavailability of anticancer agents. Furthermore, this review elucidates the design and application of polymer nanomedicines for treating hypoxic tumors, highlighting their transformative potential in cancer therapy. Finally, this article gives an outlook on stimuli-responsive polymeric nanomedicines in the treatment of oral cancer.

Targeted Cancer Therapy-on-A-Chip

Targeted cancer therapy (TCT) is gaining increased interest because it reduces the risks of adverse side effects by specifically treating tumor cells. TCT testing has traditionally been performed using two-dimensional (2D) cell culture and animal studies. Organ-on-a-chip (OoC) platforms have been developed to recapitulate cancer in vitro, as cancer-on-a-chip (CoC), and used for chemotherapeutics development and testing. This review explores the use of CoCs to both develop and test TCTs, with a focus on three main aspects, the use of CoCs to identify target biomarkers for TCT development, the use of CoCs to test free, un-encapsulated TCTs, and the use of CoCs to test encapsulated TCTs. Despite current challenges such as system scaling, and testing externally triggered TCTs, TCToC shows a promising future to serve as a supportive, pre-clinical platform to expedite TCT development and bench-to-bedside translation.

Tyrosinase-Woven Melanin Nets for Melanoma Therapy through Targeted Mitochondrial Tethering and Enhanced Photothermal Treatment

Manipulating intracellular biological processes and organelles has emerged as a pivotal strategy to influence cellular physiological functions. Mitochondria, recognized as the powerhouse of cells, play a crucial role in tumorigenesis and progression. Inspired by the Nature's tyrosinase-catalyzed melanin formation within melanoma cells, here an approach is developed using a polysaccharide dually-functionalized with tyrosine and triphenylphosphine (TPP) for targeted mitochondria cross-linking in melanoma cells. This technique intricately weaves melanin nets within the cells, serving as a tether for the mitochondria and effectively decelerating tumor metabolism through nanoparticle-net transformation. Tyrosinase acts as the "needle", while the functionalized polysaccharide serves as the "string" successfully constructing nets within the cell. Furthermore, the tyrosinase-catalyzed cross-linking of tyrosine not only facilitates the production of artificial melanin but also enhances the photothermal conversion efficiency of melanoma cells, leading to decrease of the tumor growth. This study unveils a non-drug method for regulating organelle physiological activity and introduces photothermal treatment. This work not only sheds light on the manipulation of cellular functions but also holds promise for advancing cancer therapeutic strategies.

Polyhydroxyalkanoates (PHAs) and its copolymer nanocarrier application in cancer treatment: An overview and challenges

In the modern era, nanomedicine has developed novel drug-delivery strategies to improve chemotherapy. Nanotechnological-based treatment approaches for cancer through targeted tumour drug delivery and stimulus-responsive tumour microenvironment have gained tremendous success in oncology. The application of building block materials of these nanomedicines plays a vital role in cancer remediation. Despite successful application in various medical treatments, nanocarriers' lack of biodegradability and biocompatibility makes their use in a clinical context difficult. In addition, the preparation of current drug delivery systems is a major constraint. The current cancer treatment methods aim to destroy diseased tissue, frequently with the use of radiation and chemotherapy. These treatment options are accompanied by a significant level of toxicity, which has excellent potential to further medical issues in the afflicted patient. Polyhydroxyalkanoate (PHA) polymers are biodegradable and biocompatible polyesters that can potentially be used as nanoparticular delivery systems for cancer treatment. Previously, PHA has shown tremendous application as a packaging material in the food and pharma industry. PHA-based nanocarriers are an effective drug delivery system because of their non-immunogenicity, regulated drug release, high drug loading capacity, and targeted drug delivery. This review focuses on creating and using PHA-based nanocarriers in cancer treatment. Despite its many benefits, PHA-based nanocarriers have yet to progress to clinical trials for drug delivery applications due to several issues, including the polymers' hydrophobic nature and high production costs. This review examines these challenges along with existing alternatives.

Engineering hypoxia-responsive 6-aminonicotinamide prodrugs for on-demand NADPH depletion and redox manipulation

Glucose-6-phosphate dehydrogenase (G6PD) is a promising target in cancer therapy. However, poor cellular uptake and off-target toxicity have impeded the clinical translation of a canonical G6PD inhibitor (6-aminonicotinamide/6AN). Here, we report a prodrug strategy to address this issue. The tailored 6AN prodrug contains an azo-bearing protection moiety. The hydrophobic prodrug showed increased cellular uptake than 6AN and was vulnerable to hypoxia, resulting in NAD(P)H quinone dehydrogenase 1 (NQO1)-triggered cleavage of azo bonds. Intriguingly, the prodrug showed configuration-dependent anti-cancer potency. Despite the lower thermodynamic stability, the cis isomer showed enhanced cellular uptake compared to the trans counterpart due to the increased aqueous solubility. Moreover, the boosted potency of the cis isomer compared to the trans isomer arose from the enhancement of NOQ1-catalyzed 6AN release under hypoxia, a hallmark of solid tumors. The discovery of hypoxia-responsive 6AN prodrugs in the current work opens up new avenues for G6PD-targeting cancer medicines.

Current advances in modulating tumor hypoxia for enhanced therapeutic efficacy

Hypoxia is a common feature of most solid tumors, which promotes the proliferation, invasion, metastasis, and therapeutic resistance of tumors. Researchers have been developing advanced strategies and nanoplatforms to modulate tumor hypoxia to enhance therapeutic effects. A timely review of this rapidly developing research topic is therefore highly desirable. For this purpose, this review first introduces the impact of hypoxia on tumor development and therapeutic resistance in detail. Current developments in the construction of various nanoplatforms to enhance tumor treatment in response to hypoxia are also systematically summarized, including hypoxia-overcoming, hypoxia-exploiting, and hypoxia-disregarding strategies. We provide a detailed discussion of the rationale and research progress of these strategies. Through a review of current trends, it is hoped that this comprehensive overview can provide new prospects for clinical application in tumor treatment. STATEMENT OF SIGNIFICANCE: As a common feature of most solid tumors, hypoxia significantly promotes tumor progression. Advanced nanoplatforms have been developed to modulate tumor hypoxia to enhanced therapeutic effects. In this review, we first introduce the impact of hypoxia on tumor progression. Current developments in the construction of various nanoplatforms to enhance tumor treatment in response to hypoxia are systematically summarized, including hypoxia-overcoming, hypoxia-exploiting, and hypoxia-disregarding strategies. We discuss the rationale and research progress of the above strategies in detail, and finally introduce future challenges for treatment of hypoxic tumors. By reviewing the current trends, this comprehensive overview can provide new prospects for clinical translatable tumor therapy.

Hypoxia and Singlet Oxygen Dual-Responsive Micelles for Photodynamic and Chemotherapy Therapy Featured with Enhanced Cellular Uptake and Triggered Cargo Delivery

Introduction

Combination therapy provides better outcomes than a single therapy and becomes an efficient strategy for cancer treatment. In this study, we designed a hypoxia- and singlet oxygen-responsive polymeric micelles which contain azo and nitroimidazole groups for enhanced cellular uptake, repaid cargo release, and codelivery of photosensitizer Ce6 and hypoxia-activated prodrug tirapazamine TPZ (DHM-Ce6@TPZ), which could be used for combining Ce6-mediated photodynamic therapy (PDT) and PDT-activated chemotherapy to enhance the therapy effect of cancer.

Methods

The hypoxia- and singlet oxygen-responsive polymeric micelles DHM-Ce6@TPZ were prepared by film hydration method. The morphology, physicochemical properties, stimuli responsiveness, in vitro singlet oxygen production, cellular uptake, and cell viability were evaluated. In addition, the in vivo therapeutic effects of the micelles were verified using a tumor xenograft mice model.

Results

The resulting dual-responsive micelles not only increased the concentration of intracellular photosensitizer and TPZ, but also facilitated photosensitizer and TPZ release for enhanced integration of photodynamic and chemotherapy therapy. As a photosensitizer, Ce6 induced PDT by generating toxic singlet reactive oxygen species (ROS), resulting in a hypoxic tumor environment to activate the prodrug TPZ to achieve efficient chemotherapy, thereby evoking a synergistic photodynamic and chemotherapy therapeutic effect. The cascade synergistic therapeutic effect of DHM-Ce6@TPZ was effectively evaluated both in vitro and in vivo to inhibit tumor growth in a breast cancer mice model.

Conclusion

The designed multifunctional micellar nano platform could be a convenient and powerful vehicle for the efficient co-delivery of photosensitizers and chemical drugs for enhanced synergistic photodynamic and chemotherapy therapeutic effect of cancer.

Stimuli-Responsive Polymer-Based Nanosystems for Cancer Theranostics

Stimuli-responsive polymers can respond to internal stimuli, such as reactive oxygen species (ROS), glutathione (GSH), and pH, biological stimuli, such as enzymes, and external stimuli, such as lasers and ultrasound, etc., by changing their hydrophobicity/hydrophilicity, degradability, ionizability, etc., and thus have been widely used in biomedical applications. Due to the characteristics of the tumor microenvironment (TME), stimuli-responsive polymers that cater specifically to the TME have been extensively used to prepare smart nanovehicles for the targeted delivery of therapeutic and diagnostic agents to tumor tissues. Compared to conventional drug delivery nanosystems, TME-responsive nanosystems have many advantages, such as high sensitivity, broad applicability among different tumors, functional versatility, and improved biosafety. In recent years, a great deal of research has been devoted to engineering efficient stimuli-responsive polymeric nanosystems, and significant improvement has been made to both cancer diagnosis and therapy. In this review, we summarize some recent research advances involving the use of stimuli-responsive polymer nanocarriers in drug delivery, tumor imaging, therapy, and theranostics. Various chemical stimuli will be described in the context of stimuli-responsive nanosystems. Accordingly, the functional chemical groups responsible for the responsiveness and the strategies to incorporate these groups into the polymer will be discussed in detail. With the research on this topic expending at a fast pace, some innovative concepts, such as sequential and cascade drug release, NIR-II imaging, and multifunctional formulations, have emerged as popular strategies for enhanced performance, which will also be included here with up-to-date illustrations. We hope that this review will offer valuable insights for the selection and optimization of stimuli-responsive polymers to help accelerate their future applications in cancer diagnosis and treatment.

The Role of Integrins for Mediating Nanodrugs to Improve Performance in Tumor Diagnosis and Treatment

Integrins are heterodimeric transmembrane proteins that mediate adhesive connections between cells and their surroundings, including surrounding cells and the extracellular matrix (ECM). They modulate tissue mechanics and regulate intracellular signaling, including cell generation, survival, proliferation, and differentiation, and the up-regulation of integrins in tumor cells has been confirmed to be associated with tumor development, invasion, angiogenesis, metastasis, and therapeutic resistance. Thus, integrins are expected to be an effective target to improve the efficacy of tumor therapy. A variety of integrin-targeting nanodrugs have been developed to improve the distribution and penetration of drugs in tumors, thereby, improving the efficiency of clinical tumor diagnosis and treatment. Herein, we focus on these innovative drug delivery systems and reveal the improved efficacy of integrin-targeting methods in tumor therapy, hoping to provide prospective guidance for the diagnosis and treatment of integrin-targeting tumors.

Sustained-release behavior and the antitumor effect of charge-convertible poly(amino acid)s drug-loaded nanoparticles

Enhancing tissue permeability and achieving drug aggregation is the key to targeted tumor therapy. A series triblock copolymers of poly(ethylene glycol)-poly(L-lysine)-poly(L-glutamine) were synthesized by ring-opening polymerization, and charge-convertible nano-delivery system was constructed by loading doxorubicin (DOX) with 2-(hexaethylimide) ethanol on side chain. In normal environment (pH = 7.4), the zeta potential of the drug-loaded nanoparticle solution is negative, which is conducive to avoiding the identification and clearance of nanoparticles by the reticulo-endothelial system, while potential-reversal can be achieved in the tumor microenvironment, which effectively promotes cellular uptake. Nanoparticles could effectively reduce the distribution of DOX in normal tissues and achieve targeted aggregation at tumor sites, which can effectively improve the antitumor effect, while would not causing toxicity and damage to normal body.

Exploring the Application of Micellar Drug Delivery Systems in Cancer Nanomedicine

Various formulations of polymeric micelles, tiny spherical structures made of polymeric materials, are currently being investigated in preclinical and clinical settings for their potential as nanomedicines. They target specific tissues and prolong circulation in the body, making them promising cancer treatment options. This review focuses on the different types of polymeric materials available to synthesize micelles, as well as the different ways that micelles can be tailored to be responsive to different stimuli. The selection of stimuli-sensitive polymers used in micelle preparation is based on the specific conditions found in the tumor microenvironment. Additionally, clinical trends in using micelles to treat cancer are presented, including what happens to micelles after they are administered. Finally, various cancer drug delivery applications involving micelles are discussed along with their regulatory aspects and future outlooks. As part of this discussion, we will examine current research and development in this field. The challenges and barriers they may have to overcome before they can be widely adopted in clinics will also be discussed.

Innovative nanotheranostics: Smart nanoparticles based approach to overcome breast cancer stem cells mediated chemo- and radioresistances

The alarming increase in the number of breast cancer patients worldwide and the increasing death rate indicate that the traditional and current medicines are insufficient to fight against it. The onset of chemo- and radioresistances and cancer stem cell-based recurrence make this problem harder, and this hour needs a novel treatment approach. Competent nanoparticle-based accurate drug delivery and cancer nanotheranostics like photothermal therapy, photodynamic therapy, chemodynamic therapy, and sonodynamic therapy can be the key to solving this problem due to their unique characteristics. These innovative formulations can be a better cargo with fewer side effects than the standard chemotherapy and can eliminate the stability problems associated with cancer immunotherapy. The nanotheranostic systems can kill the tumor cells and the resistant breast cancer stem cells by novel mechanisms like local hyperthermia and reactive oxygen species and prevent tumor recurrence. These theranostic systems can also combine with chemotherapy or immunotherapy approaches. These combining approaches can be the future of anticancer therapy, especially to overcome the breast cancer stem cells mediated chemo- and radioresistances. This review paper discusses several novel theranostic systems and smart nanoparticles, their mechanism of action, and their modifications with time. It explains their relevance and market scope in the current era. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Pluronic® triblock copolymer-based nanoformulations for cancer therapy: A 10-year overview

This paper provides a review of the literature on the use of Pluronic® triblock copolymers for drug encapsulation over the last 10 years. A special focus is given to the progress of drug delivery systems (e.g., micelles, liposomes, micro/nanoemulsions, hydrogels and nanogels, and polymersomes and niosomes); the beneficial aspects of Pluronic® triblock copolymers as biological response modifiers and as pharmaceutical additives, adjuvants, and stabilizers, are also discussed. The advantages and limitations encountered in developing site-specific targeting approaches based on Pluronic-based nanostructures in cancer treatment are highlighted, in addition to innovative examples for improving tumor cytotoxicity while reducing side effects.