Changying Shi

Photo and Redox Dual Responsive Reversibly Cross-Linked Nanocarrier for Efficient Tumor-Targeted Drug Delivery

To develop a feasible and efficient nanocarrier for potential clinical application, a series of photo and redox dual responsive reversibly cross-linked micelles have been developed for the targeted anticancer drug delivery. The nanocarrier can be cross-linked efficiently via a clean, efficient, and controllable coumarin photodimerization within the nanocarrier, which simplify the formulation process and quality control prior clinical use and improve the in vivo stability for tumor targeting. At the same time, cross-linking of nanocarrier could be cleaved via the responsiveness of the built-in disulfide cross-linkage to the redox tumor microenvironment for on-demand drug release. Coumarin and disulfide bond was introduced into a linear-dendritic copolymer (named as telodendrimer) precisely via peptide chemistry. The engineered nanocarrier possesses good drug loading capacity and stability, and exhibits a safer profile as well as similar anticancer effects compared with free drug in cell culture. The in vivo and ex vivo small animal imaging revealed the preferred tumor accumulation and the prolonged tumor residency of the payload delivered by the cross-linked micelles compared to the non-cross-linked micelles and free drug surrogate because of the increased stability.

A drug-specific nanocarrier design for efficient anticancer therapy

The drug-loading properties of nanocarriers depend on the chemical structures and properties of their building blocks. Here, we customize telodendrimers (linear-dendritic copolymer) to design a nanocarrier with improved in vivo drug delivery characteristics. We do a virtual screen of a library of small molecules to identify the optimal building blocks for precise telodendrimer synthesis using peptide chemistry. With rationally designed telodendrimer architectures, we then optimize the drug binding affinity of a nanocarrier by introducing an optimal drug-binding molecule (DBM) without sacrificing the stability of the nanocarrier. To validate the computational predictions, we synthesize a series of nanocarriers and evaluate systematically for doxorubicin delivery. Rhein-containing nanocarriers have sustained drug release, prolonged circulation, increased tolerated dose, reduced toxicity, effective tumor targeting and superior anticancer effects owing to favourable doxorubicin-binding affinity and improved nanoparticle stability. This study demonstrates the feasibility and versatility of the de novo design of telodendrimer nanocarriers for specific drug molecules, which is a promising approach to transform nanocarrier development for drug delivery.

Reversibly crosslinked nanocarriers for on-demand drug delivery in cancer treatment.

Polymer micelles have proven to be one of the most versatile nanocarriers for anticancer drug delivery. However, the in vitro and in vivo stability of micelles remains a challenge due to the dynamic nature of these self-assembled systems, which leads to premature drug release and nonspecific biodistribution in vivo. Recently, reversibly crosslinked micelles have been developed to provide solutions to stabilize nanocarriers in blood circulation. Increased stability allows nanoparticles to accumulate at tumor sites efficiently via passive and/or active tumor targeting, while cleavage of the micelle crosslinkages, through internal or external stimuli, facilitates on-demand drug release. In this review, various crosslinking chemistries as well as the choices for reversible linkages in these nanocarriers will be introduced. Then, the development of reversibly crosslinked micelles for on-demand drug release in response to single or dual stimuli in the tumor microenvironment is discussed, for example, acidic pH, reducing microenvironment, enzymatic microenvironment, photoirradiation and the administration of competitive reagents postmicelle delivery.

Block and random copolymers bearing cholic acid and oligo(ethylene glycol) pendant groups: aggregation, thermosensitivity, and drug loading.

A series of block and random copolymers consisting of oligo(ethylene glycol) and cholic acid pendant groups were synthesized via ring-opening metathesis polymerization of their norbornene derivatives. These block and random copolymers were designed to have similar molecular weights and comonomer ratios; both types of copolymers showed thermosensitivity in aqueous solutions with similar cloud points. The copolymers self-assembled into micelles in water as shown by dynamic light scattering and transmission electron microscopy. The hydrodynamic diameter of the micelles formed by the block copolymer is much larger and exhibited a broad and gradual shrinkage from 20 to 54 °C below its cloud point, while the micelles formed by the random copolymers are smaller in size but exhibited some swelling in the same temperature range. Based on in vitro drug release studies, 78% and 24% paclitaxel (PTX) were released in 24 h from micelles self-assembled by the block and random copolymers, respectively. PTX-loaded micelles formed by the block and random copolymers exhibited apparent antitumor efficacy toward the ovarian cancer cells with a particularly low half-maximal inhibitory concentration (IC50) of 27.4 and 40.2 ng/mL, respectively. Cholic acid-based micelles show promise as a versatile and potent platform for cancer chemotherapy.

The Use of One-Bead One-Compound Combinatorial Library Technology to Discover High-Affinity αvβ3 Integrin and Cancer Targeting Arginine-Glycine-Aspartic Acid Ligands with a Built-in Handle

The αvβ3 integrin, expressed on the surface of various normal and cancer cells, is involved in numerous physiologic processes such as angiogenesis, apoptosis, and bone resorption. Because this integrin plays a key role in angiogenesis and metastasis of human tumors, αvβ3 integrin ligands are of great interest to advances in targeted therapy and cancer imaging. In this report, one-bead one-compound (OBOC) combinatorial libraries containing the arginine-glycine-aspartic acid (RGD) motif were designed and screened against K562 myeloid leukemia cells that had been transfected with the human αvβ3 integrin gene. Cyclic peptide LXW7 was identified as a leading ligand with a built-in handle that binds specifically to αvβ3 and showed comparable binding affinity (IC50 = 0.68 ± 0.08 μmol/L) to some of the well-known RGD “head-to-tail” cyclic pentapeptide ligands reported in the literature. The biotinylated form of LXW7 ligand showed similar binding strength as LXW7 against αvβ3 integrin, whereas biotinylated RGD cyclopentapeptide ligands revealed a 2- to 8-fold weaker binding affinity than their free forms. LXW7 was able to bind to both U-87MG glioblastoma and A375M melanoma cell lines, both of which express high levels of αvβ3 integrin. In vivo and ex vivo optical imaging studies with the biotinylated ligand/streptavidin-Cy5.5 complex in nude mice bearing U-87MG or A375M xenografts revealed preferential uptake of biotinylated LXW7 in tumor. When compared with biotinylated RGD cyclopentapeptide ligands, biotinylated LXW7 showed higher tumor uptake but lower liver uptake. Mol Cancer Ther; 9(10); 2714–23. ©2010 AACR.

Rainbow beads: A color coding method to facilitate high-throughput screening and optimization of one-bead one-compound combinatorial libraries

We have developed a new color-encoding method that facilitates high-throughput screening of one-bead one-compound (OBOC) combinatorial libraries. Polymer beads displaying chemical compounds or families of compounds are stained with oil-based organic dyes that are used as coding tags. The color dyes do not affect cell binding to the compounds displayed on the surface of the beads. We have applied such rainbow beads in a multiplex manner to discover and profile ligands against cell surface receptors. In the first application, a series of OBOC libraries with different scaffolds or motifs are each color-coded; small samples of each library are then combined and screened concurrently against live cells for cell attachment. Preferred libraries can be rapidly identified and selected for subsequent large-scale screenings for cell surface binding ligands. In a second application, beads with a series of peptide analogues (e.g., alanine scan) are color-coded, combined, and tested for binding against a specific cell line in a single-tissue culture well; the critical residues required for binding can be easily determined. In a third application, ligands reacting against a series of integrins are color-coded and used as a readily applied research tool to determine the integrin profile of any cell type. One major advantage of this straightforward and yet powerful method is that only an ordinary inverted microscope is needed for the analysis, instead of sophisticated (and expensive) fluorescent microscopes or flow cytometers.

Fine-tuning vitamin E-containing telodendrimers for efficient delivery of gambogic acid in colon cancer treatment.

Certain natural products such as gambogic acid (GA) exhibit potent antitumor effects. Unfortunately, administration of these natural products is limited by their poor solubility in conventional pharmaceutical solvents. In this study, a series of telodendrimers, composed of linear polyethylene glycol (PEG)-blocking-dendritic oligomer of cholic acid (CA) and vitamin E (VE), have been designed with architectures optimized for efficient delivery of GA and other natural anticancer compounds. Two of the telodendrimers with segregated CA and VE domains self-assembled into stable cylindrical and/or spherical nanoparticles (NPs) after being loaded with GA as observed under transmission electron microscopy (TEM), which correlated with the dynamic light scattering (DLS) analysis of sub-30 nm particle sizes. A very high GA loading capacity (3:10 drug/polymer w/w) and sustained drug release were achieved with the optimized telodendrimers. These novel nanoformulations of GA were found to exhibit similar in vitro cytotoxic activity against colon cancer cells as the free drug. Near-infrared fluorescence small animal imaging revealed preferential accumulation of GA-loaded NPs into tumor tissue. The optimized nanoformulation of GA achieved superior antitumor efficacy compared to GA-Cremophor EL formulation at equivalent doses in HT-29 human colon cancer xenograft mouse models. Given the mild adverse effects associated with this natural compound and the enhanced anticancer effects via tumor targeted telodendrimer delivery, the optimized GA nanoformulation is a promising alternative to the traditional chemotherapy in colon cancer treatment.

Tunable Lipidoid‐Telodendrimer Hybrid Nanoparticles for Intracellular Protein Delivery in Brain Tumor Treatment

A strategy to precisely engineer lipidoid-telodendrimer binary hybrid nanoparticles that offer enhanced cell membrane permeability for therapeutic proteins to reach the intracellular targets is established. The highly controllable biochemical and physical properties of the nanoparticles make them promising for protein-based brain cancer treatment with the assistance of convection-enhanced delivery.

Functional-segregated coumarin-containing telodendrimer nanocarriers for efficient delivery of SN-38 for colon cancer treatment

Four coumarin-containing telodendrimers (denoted as P-I, P-II, P-III and P-IV) were designed and synthesized to self-assemble into the corresponding nanoparticles. Of those, two nanoparticles (P-II and P-IV micelles) were screened and selected for targeted drug delivery of 7-ethyl-10-hydroxy camptothecin (SN-38), a prominent and efficacious anticancer agent, for the treatment of colon cancers. The nanoparticle encapsulation significantly increased the solubility of SN-38 in aqueous solution. Dynamic light scattering (DLS) showed the size of these SN-38 nanoparticles to be around 50 nm, and rod-shaped micelles were observed using transmission electron microscopy (TEM). These two novel nanoformulations of SN-38/P-II and SN-38/P-IV were found to exhibit similar in vitro cytotoxic activity against colon cancer cells as the free drug (SN-38 in DMSO) and were 500-fold more potent than irinotecan (a prodrug of SN-38). In addition, near infrared fluorescent (NIRF) optical imaging was utilized to monitor the tumor targeted delivery of SN-38/NPs via co-loading a NIRF dye. It was demonstrated that these NPs preferentially accumulated in tumors when compared to healthy tissue. A pharmacokinetics study showed that SN-38 micelle formulations had a longer circulating time in blood than irinotecan. Furthermore, SN-38 loaded nanoformulations exhibit superior anti-tumor efficacy when compared with irinotecan at equivalent SN-38 dose in HT-29 human colon cancer xenograft models.

A structure-property relationship study of the well-defined telodendrimers to improve hemocompatibility of nanocarriers for anticancer drug delivery.

A series of telodendrimer (a linear polyethyelene glycol-block-dendritic oligo-cholic acid) have been synthesized via a bottom-up approach to optimize the hemocompatibility of the nanocarrier. Numbers of hydrophilic glycerol groups were introduced onto the polar surface of cholic acid to reduce the plasma membrane lytic activity of telodendrimers. An interesting result was observed: only an optimum number of glycerol introduced could reduce the hemolytic properties of the nanocarrier; on the contrary, more glycerols or the amino-glycerol substitution onto cholic acid significantly increased the hemolytic properties of the nanocarriers. To further elucidate the structure–property relationship, the molecular dynamic approach was used to simulate the conformation of the subunits of telodendrimers with different glycerol substitution, and the binding energies and the polar surface areas of the hairpin conformations were calculated to explain the membrane activities of nanocarriers. In addition, these telodendrimer subunits were synthesized and their membrane activities were tested directly, which validated the computational prediction and correlated with the observed hemolytic activity of nanocarriers. The glycerol substitution sustained the facial amphiphilicity of cholic acid, maintaining the superior drug loading capacity (paclitaxel and doxorubicin), stability, cell uptake, and anticancer efficacy of payloads. The in vivo optical imaging study indicated that the optimized nanocarriers can specifically deliver drug molecules to the tumor sites more efficiently than free drug administration, which is essential for the enhanced cancer treatment.