Lesan Yan

A prodrug strategy to deliver cisplatin(IV) and paclitaxel in nanomicelles to improve efficacy and tolerance

A strategy of preparing composite micelles containing both cisplatin(IV) prodrug and paclitaxel was developed, i.e., synthesizing a cisplatin(IV) conjugate and a paclitaxel conjugate starting with the same biodegradable and amphiphilic block copolymer, and co-assembling the two conjugates. The composite micelles could release effective anticancer drug cisplatin(II) upon cellular reduction and PTX via acid hydrolysis once they came into the cancerous cells. Moreover, the composite micelles displayed synergistic effect in vitro and the combination therapy in micellar dosage-form led to reduced systematic toxicity and enhanced antitumor efficacy in vivo.

Co-delivery of daunomycin and oxaliplatin by biodegradable polymers for safer and more efficacious combination therapy

An oxaliplatin pro-drug (Oxa(IV)-COOH) with an axial carboxyl group was synthesized and conjugated to biodegradable polymers with pendant hydroxyl groups to prepare polymer-Oxa(IV) conjugates. A hydrophobic anthracycline-based drug, daunorubicin (DRB) was conjugated to similar biodegradable polymers with carboxyl groups to synthesize polymer-DRB conjugates. The two drug conjugates have the similar polymer backbone and are amphiphilic; thus, they can co-assemble into composite micelles. In the composite micelles, the polymer-Oxa(IV) conjugates can release clinically widely used water soluble anticancer drug oxaliplatin (Oxa(II)) upon reduction, while polymer-DRB conjugate is thought to release DRB via acid hydrolysis in the cancer cells. In this way, combination of the hydrophilic platinum drug Oxa(II) and hydrophobic drug DRB can be realized by delivering them in one platform. Moreover, the composite micelles showed reduced systematic toxicity and greater synergistic effect than combination of small molecules of the two anticancer drugs both in vitro and in vivo; thus, this polymer based combination therapy can be useful in future clinic application.

Porous heterogeneous organic photocatalyst prepared by HIPE polymerization for oxidation of sulfides under visible light

A porous heterogeneous photocatalyst was prepared by high internal phase emulsion (HIPE) polymerization. Such porous materials have interconnected pores and enough active moieties for photocatalysis. The material demonstrated a very high catalytic efficiency and can be reused for photocatalyzed oxidation of thioanisole under visible light.

Photo-cross-linked mPEG-poly(γ-cinnamyl-L-glutamate) micelles as stable drug carriers

A functionalized L-glutamate N-carboxyanhydride monomer containing a cinnamyl moiety, γ-cinnamyl-L-glutamate N-carboxyanhydride (CLG-NCA), was prepared. Ring-opening polymerization (ROP) of CLG-NCA initiated by n-hexylamine and amino-terminated poly(ethylene glycol) (mPEG-NH2) was successfully performed with controlled polymer molecular weight and molecular weight distribution. The structures of the obtained monomer and polymers were confirmed by 1H NMR, 13C NMR and FTIR. The block copolymer mPEG-b-PCLG could self-assemble into micelles in aqueous solution which consist of a hydrophobic PCLG core and a hydrophilic mPEG shell. Under UV-irradiation at 254 nm, the photo-cross-linking process of the cinnamyl-carrying block copolymer micelles was tracked by UV-Vis spectra, 1H NMR, dynamic light scattering (DLS) and transmission electron microscopy (TEM). In vitro MTT assay demonstrated that the micelles were biocompatible to L929 cells. Paclitaxel was loaded into the micelles as a model drug. The in vitro paclitaxel release behaviors indicated that cross-linking of the micelle cores results in a slow drug release in comparison with the non-cross-linked micelles. These results indicated that the photo cross-linked mPEG-b-PCLG micelles can be used as drug carriers for intelligent drug delivery.

Synthesis of OH-Group-Containing, Biodegradable Polyurethane and Protein Fixation on Its Surface

A series of biodegradable polyurethanes containing free side hydroxyl groups (PUOH) were synthesized successfully in two steps: (1) PLA diol as soft segment, hexamethylene diisocyanate (HDI) as hard segment, and benzalpentaerythritol (BPO) as a chain extender were used to synthesize PUs with protected OH groups; (2) CF(3)COOH was used as a deprotection agent to remove the benzal groups on PU to prepare PUOH. The properties of PU and PUOH were characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), water contact angle measurement, and gel permeation chromatography (GPC). The benzal groups were removed completely in 15 min without detrimental effect on PU main chains to obtain PUOHs. 4-Azidobenzoic acid was conjugated to PUOH through its esterification with the free OH groups on PUOH. The results of immunofluorescence assay showed that the phenyl azide groups formed were capable of binding mouse IgG under UV (254 nm) irradiation in 3 min; the bound mouse IgG retained its own biological activity and could further bind the FITC-labeled anti(mouse IgG). Therefore, this material has a potential in immunofluorescence assay and related fields.

A reduction-sensitive carrier system using mesoporous silica nanospheres with biodegradable polyester as caps

Mesoporous silica nanoparticles (MSN)-polymer hybrid combined with the aliphatic biodegradable polyester caps on the surface were first developed in order to manipulate the smart intracellular release of anticancer drugs. First, poly(ethylene glycol)-b-poly(ε-caprolactone) (PEG-PCL) was successfully grafted on the surface of MSN via disulfide bonds which could cleave under a reduction environment in tumor cells. The anticancer drug doxorubicin (DOX) was encapsulated into the particle pores. The in vitro drug release profile showed that DOX release was significantly restricted by the polymer caps at pH 7.4, while it was greatly accelerated upon the addition of GSH. Cytotoxicity evaluation showed good biocompatibility with the hybrid particles. Fast endocytosis and intracellular DOX release were observed by confocal laser scanning microscopy (CLSM). The DOX-loaded particles exhibited comparable antitumor activity with free DOX towards HeLa cells and showed in a time-dependent manner. This work developed an extensive method of utilizing aliphatic biodegradable polyesters as polymer caps for MSN to control drug delivery. The paper might offer a potential option for cancer therapy.

Regulation of Conjugated Hemoglobin on Micelles through Copolymer Chain Sequences and the Protein's Isoelectric Aggregation

Amphiphilic triblock copolymers with carbonyl groups located either in the middle segment or in the third side block are synthesized by adjusting feeding sequence of the comonomers. The conjugation of hemoglobin (Hb) on the copolymer micelles is realized by condensation reactions of carbonyl with the amino groups of Hb, and the gas-binding capacity of Hb is well preserved. Interestingly, the reassembly behavior of Hb-conjugated micelles (HbM) is explored by adjusting the pH. As for triblock copolymers with a carbonyl-functionalized segment as the third block, Hb is rearranged into the inner core of micelles when the pH is adjusted close to the isoelectric point of Hb. Therefore, it may provide a new needed route for fabrication of protein carriers, which is different from the traditional encapsulation technique.

Positively charged polypeptide nanogel enhances mucoadhesion and penetrability of 10-hydroxycamptothecin in orthotopic bladder carcinoma

ABSTRACT Bladder cancer (BC) has become a serious public health problem due to its continuously rising incidence, high recurrence rate, and poor quality of life. Intravesical instillation of chemotherapy, one of common and important treatment strategy for BC, is restricted partially due to the short residence time and the low penetration ability of current antineoplastic agent formulations in clinic. Herein, a positively charged disulfide‐core‐crosslinked polypeptide nanogel of poly(l‐lysine)–poly(l‐phenylalanine‐co‐l‐cystine) (PLL–P(LP‐co‐LC)) was synthesized. 10‐Hydroxycamptothecin (HCPT) was loaded into the core via a facile diffusion to obtain loading nanogel (i.e., NG/HCPT). The reduction‐responsive cationic polypeptide nanogel not only showed a high drug‐loading efficiency, a prolonged residence time, and an improved tissue penetration capability, but also demonstrated an ability to accurately and rapidly release HCPT in bladder cancer cells. NG/HCPT exhibited superior cytotoxicity against human T24 bladder cancer cells compared to that of free HCPT in vitro. Moreover, the positively charged loading nanogel exhibited significantly enhanced antitumor efficacy and reduced side effects toward orthotopic bladder cancer model in vivo. Overall, the smart polypeptide nanogel with enhanced residence and permeability provides a promising drug delivery platform for local chemotherapy of BC. Graphical abstract Figure. No caption available.

Guanidinated amphiphilic cationic copolymer with enhanced gene delivery efficiency

The lack of safe and effective carriers for RNA interference therapeutics remains a barrier for its wide clinical application. In this study, guanidino groups were incorporated into poly(ethylene glycol)-block-poly(e-caprolactone)-block-poly(L-lysine) (mPEG-b-PCL-b-PLL, AG0) by simple replacement of the amino groups on PLL segments by the guanidino groups to enhance the transfection performance by mimicking the transmembrane function of cell penetrating peptides, such as TAT or other arginine-rich peptides. The guanidinated copolymers (AG1–AG3) displayed similar siRNA-binding capacity to AG0, but less cytotoxicity and higher silencing efficiency than AG0. Typically, AG3 with full replacement of the amino groups by guanidino groups exhibited higher silencing efficiency than PEI-25k and Lipofectamine 2000. Cell uptake and cell imaging experiments showed that the enhanced silencing efficiency of AG3–siRNA complex was due to the enhanced endocytosis cross the cell-membrane and the enhanced escape from the endosomes/lyosomes. The guanidino groups on the polylysine units were responsible for these enhancements although they are attached to the polymer backbone with a spacer of (CH2)4, in comparison with (CH2)3 in polyarginine. In conclusion, guanidination of mPEG-b-PCL-b-PLL resulted in a less toxic and more efficient siRNA vector and contribution of the guanidine groups to cell-membrane penetration and endosome/lyosome-membrane penetration was demonstrated. Therefore, replacement of the amino groups in conventional gene delivery vectors with guanidine groups might be a useful strategy of developing novel gene or drug delivery vectors.

A biodegradable polymer platform for co-delivery of clinically relevant oxaliplatin and gemcitabine

Anticancer drugs of gemcitabine and oxaliplatin combined in a clinic regimen (GEMOX regimen) were co-loaded to a biodegradable polymer platform for drug delivery.