Synthetic Receptor-Based Targeting Strategies to Improve Tumor Drug Delivery

HA-Coated PLGA Nanoparticles Loaded with Apigenin for Colon Cancer with High Expression of CD44

Apigenin (API) possesses excellent antitumor properties but its limited water solubility and low bioavailability restrict its therapeutic impact. Thus, a suitable delivery system is needed to overcome these limitations and improve the therapeutic efficiency. Poly (lactic-co-glycolic acid) (PLGA) is a copolymer extensively utilized in drug delivery. Hyaluronic acid (HA) is a major extracellular matrix component and can specifically bind to CD44 on colon cancer cells. Herein, we aimed to prepare receptor-selective HA-coated PLGA nanoparticles (HA-PLGA-API-NPs) for colon cancers with high expression of CD44; chitosan (CS) was introduced into the system as an intermediate, simultaneously binding HA and PLGA through electrostatic interaction to facilitate a tighter connection between them. API was encapsulated in PLGA to obtain PLGA-API-NPs, which were then sequentially coated with CS and HA to form HA-PLGA-API-NPs. HA-PLGA-API-NPs had a stronger sustained-release capability. The cellular uptake of HA-PLGA-API-NPs was enhanced in HT-29 cells with high expression of CD44. In vivo, HA-PLGA-API-NPs showed enhanced targeting specificity towards the HT-29 ectopic tumor model in nude mice in comparison with PLGA-API-NPs. Overall, HA-PLGA-API-NPs were an effective drug delivery platform for API in the treatment of colon cancers with high expression of CD44.

"Targeting Design" of Nanoparticles in Tumor Therapy

Tumor-targeted therapy based on nanoparticles is a popular research direction in the biomedical field. After decades of research and development, both the passive targeting ability of the inherent properties of NPs and the active targeting based on ligand receptor interaction have gained deeper understanding. Unfortunately, most targeted delivery strategies are still in the preclinical trial stage, so it is necessary to further study the biological fate of particles in vivo and the interaction mechanism with tumors. This article reviews different targeted delivery strategies based on NPs, and focuses on the physical and chemical properties of NPs (size, morphology, surface and intrinsic properties), ligands (binding number/force, activity and species) and receptors (endocytosis, distribution and recycling) and other factors that affect particle targeting. The limitations and solutions of these factors are further discussed, and a variety of new targeting schemes are introduced, hoping to provide guidance for future targeting design and achieve the purpose of rapid transformation of targeted particles into clinical application.

A novel self-targeting theranostic nanoplatform for photoacoustic imaging-monitored and enhanced chemo-sonodynamic therapy

Sonodynamic therapy has attracted wide attention as a noninvasive therapy due to deep tissue penetration. However, majority sonosensitizers often suffer from poor physiological stability, rapid blood clearance and nonspecific targeting, which seriously hinders their further practical applications. Inspired by the concept of active targeting drug delivery, both dual-functional chemo-drug pemetrexed (PEM, emerges an innate affinity toward the folate receptor) and amphiphilic d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) were selected to be covalently linked by an esterase-responsive ester linkage. The synthesized self-targeting TPGS-PEM prodrug and indocyanine green (ICG) as functional motifs can be self-assembled into a TPGS-PEM-ICG nanoplatform within an aqueous medium. The TPGS-PEM-ICG nanoplatform with outstanding structural and physiological stability not only protects the sonosensitizer from reticular endothelial system clearance but also achieves active targeting drug delivery and efficient tumor enrichment. Moreover, TPGS-PEM-ICG nanoplatform can selectively recognize tumor cells and then realize on-demand drug burst release by multiple stimuli of internal lysosomal acidity, esterase and external ultrasound, which guarantee low side effects toward normal tissues and organs. It is also worth noting that our nanoplatform exhibits protruding tumor enrichment under the precise guidance of photoacoustic/fluorescence imaging. Further in vitro and in vivo experimental results well confirmed that the TPGS-PEM-ICG nanoplatform possesses enhanced chemo-sonodynamic effects. Interestingly, the highly toxic reactive oxygen species can remarkably reduce the blood oxygen saturation signal of the tumor microenvironment via precise, multifunctional and high-resolution photoacoustic imaging. Taken together, the TPGS-PEM-ICG nanoplatform can be expected to hold enormous potential for diagnosis, prognosis and targeted therapy for tumor.