Tumor Microenvironment-Activated and Viral-Mimicking Nanodrugs Driven by Molecular Precise Recognition for dNTP Inhibition-Induced Synergistic Cancer Therapy

Research progress in tumor therapy of carrier-free nanodrug

Carrier-free nanodrugs are a novel type of drug constructed by the self-assembly of drug molecules without carrier involvement. They have the characteristics of small particle size, easy penetration of various barriers, targeting tumors, and efficient release. In recent years, carrier-free nanodrugs have become a hot topic in tumor therapy as they solve the problems of low drug loading, poor biocompatibility, and low uptake efficiency of carrier nanodrugs. A series of recent studies have shown that carrier-free nanodrugs play a vital role in the treatment of various tumors, with similar or better effects than carrier nanodrugs. Based on the literature published in the past decades, this paper first summarizes the recent progress in the assembly modes of carrier-free nanodrugs, then describes common therapeutic modalities of carrier-free nanodrugs in tumor therapy, and finally depicts the existing challenges along with future trends of carrier-free nanodrugs. We hope that this review can guide the design and application of carrier-free nanodrugs in the future.

Enhancing the therapeutic efficacy of nanoparticles for cancer treatment using versatile targeted strategies

Poor targeting of therapeutics leading to severe adverse effects on normal tissues is considered one of the obstacles in cancer therapy. To help overcome this, nanoscale drug delivery systems have provided an alternative avenue for improving the therapeutic potential of various agents and bioactive molecules through the enhanced permeability and retention (EPR) effect. Nanosystems with cancer-targeted ligands can achieve effective delivery to the tumor cells utilizing cell surface-specific receptors, the tumor vasculature and antigens with high accuracy and affinity. Additionally, stimuli-responsive nanoplatforms have also been considered as a promising and effective targeting strategy against tumors, as these nanoplatforms maintain their stealth feature under normal conditions, but upon homing in on cancerous lesions or their microenvironment, are responsive and release their cargoes. In this review, we comprehensively summarize the field of active targeting drug delivery systems and a number of stimuli-responsive release studies in the context of emerging nanoplatform development, and also discuss how this knowledge can contribute to further improvements in clinical practice.

Tumor Microenvironment Sensitive Nanocarriers for Bioimaging and Therapeutics

The tumor microenvironment (TME), which is composed of cancer cells, stromal cells, immune cells, and extracellular matrices, plays an important role in tumor growth and progression. Thus, targeting the TME using a well-designed nano-drug delivery system is emerging as a promising strategy for the treatment of solid tumors. Compared to normal tissues, the TME presents several distinguishable physiological features such as mildly acidic pH, hypoxia, high level of reactive oxygen species, and overexpression of specific enzymes, that are exploited as stimuli to induce specific changes in the nanocarrier structures, and thereby facilitates target-specific delivery of imaging or chemotherapeutic agents for the early diagnosis or effective treatment, respectively. Recently, smart nanocarriers that respond to more than one stimulus in the TME have also been designed to elicit a more desirable spatiotemporally controlled drug release. This review highlights the recent progress in TME-sensitive nanocarriers designed for more efficient tumor therapy and imaging. In particular, the design strategies, challenges, and critical considerations involved in the fabrication of TME-sensitive nanocarriers, along with their in vitro and in vivo evaluations are discussed.

Selective antitumor activity of drug-free TPGS nanomicelles with ROS-induced mitochondrial cell death

D-a-tocopheryl polyethylene glycol succinate (TPGS) as a FDA-approved safe adjuvant has shown an excellent application in the targeting delivery of antitumor drugs and overcoming multidrug resistance. Beside, TPGS can result in apoptogenic activity toward many tumor types because it can induce mitochondrial dysfunction. Therefore, TPGS can serve as an antineoplastic agent. However, the current research on the selective antitumor activity of TPGS is ignored. To reveal the issue, herein we develop a mitochondria-targeting drug-free TPGS nanomicelles with the hydrodynamic diameter of about 100 nm and outstanding serum stability by weak interaction-driven self-assembly of the amphiphilic TPGS polymer. Moreover, such drug-free TPGS nanomicelles intravenously injected into tumor-bearing mice exhibit long blood circulation time, superior tumor enrichment, and inhibit the tumor growth via inducing excessive reactive oxygen species (ROS) generation within tumor cells. Further in vitro and in vivo researches jointly demonstrate that drug-free TPGS nanomicelles have more significant antitumor effect on HeLa cells compared with that of other tumor cells. On the contrary, drug-free TPGS nanomicelles display the low toxicity toward normal cells and tissues. Taken together, these new findings confirm that TPGS drug-free nanomicelles represent simple, multifunctional, safe, and efficient antineoplastic agents, which can be expected to bring new light on the development of drug-free polymers for tumor therapy.

Self-Assembled Organic Nanomaterials for Drug Delivery, Bioimaging, and Cancer Therapy

Over the past few decades, tremendous progress has been made in the development of engineering nanomaterials, which opened new horizons in the field of diagnosis and treatment of various diseases. In particular, self-assembled organic nanomaterials with intriguing features including delicate structure tailoring, facile processability, low cost, and excellent biocompatibility have shown outstanding potential in biomedical applications because of the enhanced permeability and retention (EPR) effect and multifunctional properties. In this review, we briefly introduce distinctive merits of self-assembled organic nanomaterials for biomedical applications. The main focus will be placed on summarizing recent advances in self-assembled organic nanomedicine for drug delivery, bioimaging, and cancer phototherapy, followed by highlighting a critical perspective on further development of self-assembled organic nanomaterials for future clinical translation. We believe that the above themes will appeal to researchers from different fields, including material, chemical, and biological sciences, as well as pharmaceutics.