Intertumoral and intratumoral barriers as approaches for drug delivery and theranostics to solid tumors using stimuli-responsive materials

The solid tumors provide a series of biological barriers in cellular microenvironment for designing drug delivery methods based on advanced stimuli-responsive materials. These intertumoral and intratumoral barriers consist of perforated endotheliums, tumor cell crowding, vascularity, lymphatic drainage blocking effect, extracellular matrix (ECM) proteins, hypoxia, and acidosis. Triggering opportunities have been drawn for solid tumor therapies based on single and dual stimuli-responsive drug delivery systems (DDSs) that not only improved drug targeting in deeper sites of the tumor microenvironments, but also facilitated the antitumor drug release efficiency. Single and dual stimuli-responsive materials which are known for their lowest side effects can be categorized in 17 main groups which involve to internal and external stimuli anticancer drug carriers in proportion to microenvironments of targeted solid tumors. Development of such drug carriers can circumvent barriers in clinical trial studies based on their superior capabilities in penetrating into more inaccessible sites of the tumor tissues. In recent designs, key characteristics of these DDSs such as fast response to intracellular and extracellular factors, effective cytotoxicity with minimum side effect, efficient permeability, and rate and location of drug release have been discussed as core concerns of designing paradigms of these materials.

pH-Sensitive Polycations for siRNA Delivery: Effect of Asymmetric Structures of Tertiary Amine Groups

pH-sensitive polyelectrolytes provide enormous opportunity for siRNA delivery. Especially, their tertiary amine structures can not only bind genes but also act as pH-sensitive hydrophobic structure to control genes release. However, the influence of molecular structures on siRNA delivery still remains elusive, especially for the asymmetric alkyl substituents of the tertiary amine groups. Herein, a library of N-methyl-N-alkyl aminoethyl methacrylate monomers (MsAM) with asymmetric alkyl substituents on the tertiary amine group is synthesized and used to prepare a series of tri-block polycationic copolymers poly(aminoethyl methacrylate)-block-poly (N-methyl-N-alkyl aminoethyl methacrylate)-block-poly(ethylene glycol methacrylate) (PAMA-PMsMA-PEG). And the properties of these polycations and their self-assembled micelles are characterized, including molecular structure, proton buffering capacity, pH-sensitivity, size, and zeta potential. With the length increase of one alkyl substituent, the proton buffering capacity of both monomers and polycations is demonstrated to be narrowed down. The siRNA delivery efficiency and cytotoxicity of these micelles are also evaluated on HepG2 cells. In particular, poly(aminoethyl methacrylate)-block-poly(N-methyl-N-ethyl aminoethyl methacrylate)-block-poly(ethylene glycol methacrylate) (PAMA-PMEMA-PEG) elicited the best luciferase knockdown efficiency and low cytotoxicity. Besides, PAMA-PMEMA-PEG/siRRM2 also induced significant anti-tumor activity in vitro. These results indicated PAMA-PMEMA-PEG has potential for further use in the design of gene vehicles with the improved efficiency of siRNA delivery.

Antifouling hydrogel-coated magnetic nanoparticles for selective isolation and recovery of circulating tumor cells

For reliable downstream molecular analysis, it is crucially important to recover circulating tumor cells (CTCs) from clinical blood samples with high purity and viability. Herein, magnetic nanoparticles coated with an antifouling hydrogel layer based on the polymerization method were developed to realize cell-friendly and efficient CTC capture and recovery. Particularly, the hydrogel layer was fabricated by zwitterionic sulfobetaine methacrylate (SBMA) and methacrylic acid (MAA) cross-linked with N,N-bis(acryloyl)cystamine (BACy), which could not only resist nonspecific adhesion but also gently recover the captured cells by glutathione (GSH) responsiveness. Moreover, the anti-epithelial cell adhesion molecule (anti-EpCAM) antibody was modified onto the surface of the hydrogel to provide high specificity for CTC capture. As a result, 96% of target cells were captured in the mimic clinical blood samples with 5-100 CTCs per mL in 25 min of incubation time. After the GSH treatment, about 96% of the obtained cells were recovered with good viability. Notably, the hydrogel-coated magnetic nanoparticles were also usefully applied to isolate CTCs from the blood samples of cancer patients. The favorable results indicate that the hydrogel-modified magnetic nanoparticles may have a promising opportunity to capture and recover CTCs for subsequent research.

Orally delivered targeted nanotherapeutics for the treatment of colorectal cancer

INTRODUCTION

Colorectal cancer (CRC), the third-most common malignancy, has high morbidity and mortality. Oral nanotherapeutics have emerged as a promising strategy to improve the therapeutic outcomes and alleviate the adverse effects of drugs in CRC treatment.

AREAS COVERED

In this review, we introduce the beneficial features of oral drug administration for CRC therapy, and further address the three basic elements of nanotherapeutics, namely, therapeutic agents, carrier materials, and targeting ligands. In addition, we also discuss the potentials of the new emerging technologies (e.g., immunotherapy, gene editing and microbiota manipulation) in the treatment of CRC.

EXPERT OPINION

Orally delivered targeted nanotherapeutics represent a promising strategy toward the efficient treatment of CRC. Although the current oral nanotherapeutics exert better therapeutic outcomes than the traditional drug formulations, their application has been restricted by drug resistance, tumor metastasis, and biosafety. Therefore, it is necessary to exploit new nanotherapeutics in the aspects of their three basic elements, and combine the new emerging technologies to those nanotherapeutics for CRC treatment.

Structural exploration of hydrophobic core in polycationic micelles for improving siRNA delivery efficiency and cell viability

Improving siRNA delivery efficiency often encounters a dilemma with poor or decreased biocompatibility for polycationic micelles.

A two-photon fluorophore labeled multi-functional drug carrier for targeting cancer therapy, inflammation restraint and AIE active bioimaging

Functional drug carriers with simultaneous effective delivery of therapeutic agents to target sites and great imaging ability have attracted great attention in nanomedicine research.

A surface charge dependent enhanced Th1 antigen-specific immune response in lymph nodes by transfersome-based nanovaccine-loaded dissolving microneedle-assisted transdermal immunization

The efficient delivery of vaccines to draining lymph nodes and the induction of robust local immune responses are crucial for immunotherapy.

Multifunctional luminescent immuno-magnetic nanoparticles: toward fast, efficient, cell-friendly capture and recovery of circulating tumor cells

Highly efficient isolation and recovery of viable circulating tumor cells (CTCs) from the blood of patients is an important precondition to address the current dilemma of insufficient CTC studies, and can promote the development of individualized antitumor therapies. Herein, a cell-friendly CTC isolation and recovery nanoplatform with luminescent labelling was established using a layer-by-layer (LbL) assembly technique and a stimulated cellular-release strategy. In particular, the anti-epithelial cell adhesion molecule (anti-EpCAM) antibody was introduced with a disulfide bond-containing linker for further bio-friendly recovery of the CTCs. Quantum dots (QDs) were deposited onto fast magnet-responsive Fe₃O₄ nanoparticles through a facile LbL assembly method to monitor the capture and recovery process in real time. The obtained PEGlyated immuno-magnetic nanospheres (PIMNs) can all be magnetically collected within 2 min. Capture efficiencies above 90% can be achieved from blood samples with 5-200 CTCs per mL after only 1-2 min incubation. Nearly all PIMNs on the surface of the CTCs were detached after 15 min of glutathione (GSH) treatment with the disappearance of QD signals. Recovered CTCs could be directly used for culture (cell viability, ∼98%), and their invasiveness and migration characteristics remained unchanged. Furthermore, the PIMNs were successfully applied to isolate CTCs in cancer patients' peripheral blood samples, and an average of 8.6 ± 5.8 CTCs per mL was detected. The results above suggested that PIMNs may serve as a powerful nanoplatform for CTC screening, isolation and recovery.