Development of nanosized assemblies for biomedical applications
Date of Issue2018-02-09
School of Physical and Mathematical Sciences
Recently, self-assembled nanostructures have received considerable attention due to their potential applications in nanomedicine. Despite the initial success, it is still ongoing challenges to fabricate more effective and specific nanoplatforms for disease treatment and essential physiological processes investigation in living system. Therefore, various artificial and natural self-assemblies are highly desirable, and extensive strategies still need to be further exploited in clinics. To solve this problem, in this dissertation, we fabricated two different kinds of significant self-assembles, artificial peptide-based nanoconjugates and natural extracellular vesicles-based nanostructures. The former strategy was designed to overcome a major challenge, multidrug resistance (MDR), which is considered as a huge obstacle for effective cancer treatment in clinics. More importantly, the second approach was specifically constructed to introduce functional proteins from parent cells to defective recipient cells, which could be utilized to precisely manipulate cellular functions for several human diseases related to defects in membrane proteins. The relevant details are shown in the following parts. Firstly, in chapter 2, smart peptide self-assemblies are designed to reverse MDR effect in chemotherapy. As a well-known mechanism for MDR, overexpression of the drug efflux transporter, P-glycoprotein (P-gp), could significantly pump out the exogenous therapeutic drugs from cancer cells and induce the drug resistance in tumor treatment. Herein, we fabricated a reduction-responsive nanosystem based on peptide assembles, which including two bioactive molecules (an antitumor drug and a peptide inhibitor of P-gp) for combating MDR of cancer cells. Upon internalization, the nanostructures could disassemble in respond to the intracellular reductive condition, leading to the controlled release of the anticancer drug and P-gp inhibitor, which synergistically improved the therapeutic efficacy. In order to further enhance the cancer treatment efficiency, a novel tumor microenvironment-responsive nanoconjugate was developed in chapter 3 based on the pH activatable doxorubicin prodrug and another P-gp inhibitor. This inhibitor-encapsulated nanogel exhibited rapid responsiveness, controlled cargoes release, and effective inhibition of the P-gp activity, thereby significantly enhancing the accumulation of the antitumor drugs in resistant cancer cells. The synergetic effect of the P-gp inhibitor and the chemotherapeutics successfully defeated resistant cancer cells. Moreover, in addition to modulate the pathological processes via artificial peptide assemblies, we further explored the natural nanosized assemblies for manipulation of cellular functions based on specific membrane proteins. Currently, a number of major human diseases are related to defects in membrane proteins. However, effective strategies to restore the defective cellular functions from parent cells to target cells are highly desirable. Despite genetic engineering and protein transport techniques are commonly used in biomedical studies, some unavoidable limitations still occur in these approaches, including potential gene mutation and complicated protein purification steps. To overcome these drawbacks, in chapter 4, we designed a simple and efficient strategy based on EVs for transferring bioactive proteins to target cells and conferring the cells with specific biological function. To proof the concept, a light-gated membrane channel protein (ChR2) was transported to another recipient cells by using EVs nanovehicles. Upon blue light irradiation, the membrane protein was activated, allowing the calcium ion (Ca2+) influx across the plasma membrane and intracellular Ca2+-dependent transcription factors activation. The results demonstrated that our strategy provided a novel insight on the manipulation of membrane functions, which is benefit for several relevant human disease treatments in the future. Furthermore, in chapter 5, in order to investigate this dynamic behavior of EVs, a universal membrane modification strategy based on metabolic glycol-engineering was proposed for effective EVs labeling and investigating the interaction between different types of EVs and cells. Preliminary results demonstrated that the metabolic passway could effectively introduce azide groups to the surface of EVs. Moreover, bioorthogonal click chemistry allowed imaging agents to be covalently conjugated on the surface of modified EVs. Therefore, the present azide-incorporated MVs could be endowed with various imaging agents via bioorthogonal click chemistry for extensive investigation of the biological behaviors of EVs in future. In summary, these proposed strategies in this dissertation provided a prospective future of these artificially and naturally self-assembled nanostructures for the biomedical applications. We believe the present works will lead to inspiring innovations in this research field and will be developed continuously to benefit human health in the future.