Weilin Sun

Tumor Redox Heterogeneity‐Responsive Prodrug Nanocapsules for Cancer Chemotherapy

A prodrug forms nanocapsules responsive to tumor GSH/ROS heterogeneity releasing the parent drug SN38 via thiolysis in the presence of GSH (glutathione) or via enhanced hydrolysis due to ROS (reactive oxygen species)-oxidation of the linker, giving rise to high in vitro cytotoxicity and in vivo anticancer therapeutic activity. The nanocapsules are a suitable size for tumor targeting by means of the EPR effect and have a fixed SN38 loading content of 35 wt%, ideal for translational nanomedicine.

The Role of Micelle Size in Tumor Accumulation, Penetration, and Treatment

The specific sizes that determine optimal nanoparticle tumor accumulation, penetration, and treatment remain inconclusive because many studies compared nanoparticles with multiple physicochemical variables (e.g., chemical structures, shapes, and other physical properties) in addition to the size. In this study, we synthesized amphiphilic block copolymers of 7-ethyl-10-hydroxylcamptothecin (SN38) prodrug and fabricated micelles with sizes ranging from 20 to 300 nm from a single copolymer. The as-prepared micelles had exactly the same chemical structures and similar physical properties except for size, which provided an ideal platform for a systematic investigation of the size effects in cancer drug delivery. We found that the micelles blood circulation time and tumor accumulation increased with the increase in their diameters, with optimal diameter range of 100 to 160 nm. However, the much higher tumor accumulation of the large micelles (100 nm) did not result in significantly improved therapeutic efficacy, because the large micelles had poorer tumor penetration than the small ones (30 nm). An optimal size that balances drug accumulation and penetration in tumors is critical for improving the therapeutic efficacy of nanoparticulate drugs.

Poly(ionic liquid)s: a new material with enhanced and fast CO2 absorption

Novel sorbent and membrane materials for CO2 separation, poly(ionic liquid)s made from ionic liquid monomers, poly[p-vinylbenzyltrimethyl ammonium tetrafluoroborate](P[VBTMA][BF4]) and poly[2-(methacryloyloxy)ethyltrimethylamnonium tetrafluoroborate](P[MATMA][BF4]) have absorption capacities 7.6 and 6.0 times of those of room-temperature ionic liquids, e.g.[bmim][BF4], respectively, with reversible and fast sorption and desorption.

Regulation of biodegradability and drug release behavior of aliphatic polyesters by blending

Polyester blending of poly(epsilon-caprolactone) (PCL) with poly(D, L-lactide) (PLA) and their random copolymers (R(CL/LA)) was found to be a convenient approach to regulate the degradation and drug release behaviors of the polyesters. The blend composition and compatibility both affected its degradation and drug release behavior. A DSC study showed that PCL was compatible with 50:50 poly(CL-CO-D,L-LA) (R(50/50)) but incompatible with 25:75 poly(CL-CO-LA) (R(25/75)) and PLA homopolymer. The hydrolysis experiments indicated that with the same CL/LA segment proportion, compatible blends (PCL/R(50/50)) had higher water content and faster weight loss than incompatible blends (PCL/PLA, PCL/R(25/75)). In the compatible blends the PCL degradation rate was increased while that of R(50/50) was decreased. The controlled release kinetics, diffusion constants, and permeation coefficients of the polymer blends were measured by using northindrone (NTD) as a model. The NTD release rates from the polyester blends increased as the CL unit fraction increased but decreased with increasing the LA unit fraction in the blends. With the same CL/LA unit ratios, the NTD release rate from the compatible blend was slower than that from the incompatible blend. The NTD release from the polyester blend was controlled by the diffusion process in the early stage, but the degradation-caused NTD release was later involved. By tailoring the blend composition to such an extent that the degradation-caused release compensated the decline of the diffusion-caused release, a zero-order NTD release was achieved.

Synthesis and Crystal Structure of a Cadmium(II) Complex with 2,2′-diamino-4,4′-bis-1,3-thiazole

Crystals of the title complex with diaminobithiazole (DABT) were obtained by a solution diffusion method. X-ray diffraction analysis shows the complex to be monoclinic, space group P21/c with cell dimensions a=11.684(2), b=13.625(2), c=14.859(1) Å and β=109.970(7)°; R=0.026. The Cd(II) atom lies in a distorted octahedral environment with two DABT and two Cl ligands in a cis arrangement. The average internal dihedral angle of 9.3° between thiazole rings of DABT shows the twisted structure of the ligand in the complex. The Cd(II) atom deviates by some -0.570 Å from the mean plane of the thiazole ring containing N(4), but the Cd-N(4) bond is the shortest among four Cd-N bonds in the structure. Intramolecular H-bonds between Cl atoms and amino groups stabilize the cis-configuration of the complex.

Single-wall carbon manotubes as immobilization material for glucose biosensor

An application of carbon nanotubes as immobilization materials for biosensor was described for the first time. Single-wall carbon nanotubes (SWNTs) functionalized with carboxylic acid groups were cast on platinum electrode. The film of SWNTs was used to immobilize glucose oxidase by covalent combine method forming a glucose biosensor. The biosensor showed stable amperometric response at a low applied potential (0.40 V), a wide response range of pH (5.5-8) and good stability (kept 90% activity after 4 months).

A novel bithiazole-tetrathiapentalene polymer and its metal complexes

Abstract This paper describes the synthesis of a novel heterocyclic polymer incorporating both bithiazole and tetrathiapentalene moieties in the main chain. The complexion of the polymer with FeSO 4 or NdCl 3 in dimethyl sulfoxide produced corresponding metal complexes. Based on IR spectra and X-ray photoelectron spectroscopy (XPS) data the structure of these metal complexes is discussed briefly. The magnetic properties of the metallopolymers were measured as a function of magnetic field strength (0–60 kOe) at 5 K and as a function of temperature (5–300 K) under an applied magnetic field of 30 kOe, respectively. The neodymium complex exhibits a hysteresis cycle at 5 K, the observed coercivity H c and the remnant magnetization M r are 15 Oe and 0.00035 emu/g, respectively.

Copolymerization of N-phenylmaleimide with styrene by rare earth coordination catalyst

Abstract The copolymerization of N -phenylmaleimide (NPMI) with styrene (St) was studied with a rare earth coordination catalyst Nd(naph) 3 –AlEt 3 in toluene at 50 °C. The compositions of the two monomers in copolymers were close to 1:1 even at a high monomer conversion of about 60%, and did not change as the NPMI feed mole fraction varied from 10% to 90%. The copolymer was characterized by 13 C nuclear magnetic resonance spectroscopy, showing that the copolymer possessed a nearly alternating structure. The thermal properties of the copolymers were also investigated. It was presumed that a charge transfer complex of NPMI and St participated in the polymerization process.

Synthesis and magnetic properties of complexes of a conjugated hyperbranched polymer containing bithiazole rings

A novel conjugated hyperbranched polymer containing bithiazole rings (PBTADB) was synthesized by polycondensation of 1,3,5-benzenetricarboxaldehyde and 2,2′-diamino-4,4′-bithiazole (DABT). The structure of the hyperbranched polymer was confirmed by FT-IR and 1H-NMR. PBTADB dissolved in organic polar solvents such as DMSO and NMP. Bithiazole rings were introduced to provide bidentate N-donor sites for binding metal ions. The metal complexes were prepared by chelation of the polymer with Co2+ and Sm3+. The magnetic behavior of coordination compounds was measured as a function of magnetic field strength (0−4.8 × 106 A/m) at 5 K and as a function of temperature (5–300 K) at magnetic field strength of 2.4 × 106 A/m. The magnetic hysteresis loops of PBTADB-Sm3+ and PBTADB-Co2+ showed the typical ‘S’ shape at 5 K with the Curie-Weiss temperature Tθ = 96 K and 41 K respectively. The results show that they exhibit properties of soft ferromagnetic materials.

HETEROCYCLIC SCHIFF BASE NEODYMIUM COMPLEX AS CATALYST FOR RING-OPENING POLYMERIZATION OF ε-CAPROLACTONE *

An aromatic heterocyclic Schiff base neodymium complex bearing thiazole was synthesized and its activity in the ring-opening polymerization of e-caprolactone (CL) was examined. The conditions of the CL/Nd molar ratio, monomer concentration, polymerization time and temperature were investigated. Activities of ca.171 kg/Nd·h were obtained under the optimum condition (CL/Nd = 1600 (molar ratio), [CL] = 2.26 mol L-1, 1 h at 50°C), giving a poly(e-caprolactone) (PCL) of number-average molecular weight Mn= 5.4 × 104 and molecular weight distribution MWD = 1.96. The conversion of CL monomer as high as 94% was observed after polymerized for one hour. The mechanism of coordination polymerization has also been illustrated.