Preparation of Crosslinked Chitosan/Silk Fibroin Blend Films for Drug Delivery System

Crosslinked chitosan/silk fibroin blend films were prepared by a solution casting technique using glutaraldehyde as crosslinking agent. Drug release characteristics of the blend films with various blend compositions were investigated. Theophylline, diclofenac sodium, amoxicillin trihydrate, and salicylic acid were used as model drugs. The release studies were performed at 37 °C in buffer solutions at pH 2.0, 5.5, and 7.2. It was found that the blend films with 80% chitosan content showed the maximum amount of model drug release at pH 2.0 for all the drugs studied here. This result corresponded to the swelling ability of the blend films. From a swelling study, the maximum degrees of swelling of the drug‐loaded blend films were obtained at this pH and blend composition. The amount of drugs released from the films with 80% chitosan content, from the highest to the lowest values, occurred in the following sequence: salicylic acid > theophylline > diclofenac sodium > amoxicillin.

Comparison of the amounts of drug released from chitosan and the blend film with 80% chitosan content at pH 2.0: (filled) chitosan film, and (blank) blend film with 80% chitosan content (SAL = salicylic acid, THEO = theophylline, DFS = diclofenac sodium, AMX = amoxicillin).     

Preparation and Characterization of Natural Silk Fibroin Hydrogel for Protein Drug Delivery

In recent years, hydrogels have been widely used as drug carriers, especially in the area of protein delivery. The natural silk fibroin produced from cocoons of the Bombyx mori silkworm possesses excellent biocompatibility, significant bioactivity, and biodegradability. Therefore, silk fibroin-based hydrogels are arousing widespread interest in biomedical research. In this study, a process for extracting natural silk fibroin from raw silk textile yarns was established, and three aqueous solutions of silk fibroin with different molecular weight distributions were successfully prepared by controlling the degumming time. Silk fibroin was dispersed in the aqueous solution as “spherical” aggregate particles, and the smaller particles continuously accumulated into large particles. Finally, a silk fibroin hydrogel network was formed. A rheological analysis showed that as the concentration of the silk fibroin hydrogel increased its storage modulus increased significantly. The degradation behavior of silk fibroin hydrogel in different media verified its excellent stability, and the prepared silk fibroin hydrogel had good biocompatibility and an excellent drug-loading capacity. After the protein model drug BSA was loaded, the cumulative drug release within 12 h reached 80%. We hope that these investigations will promote the potential utilities of silk fibroin hydrogels in clinical medicine.     

Effect of Silk Protein Processing on Drug Delivery from Silk Films

Sericin removal from the core fibroin protein of silkworm silk is a critical first step in the use of silk for biomaterial‐related applications, but degumming can affect silk biomaterial properties, including molecular weight, viscosity, diffusivity and degradation behavior. Increasing the degumming time (10, 30, 60, and 90 min) decreases the average molecular weight of silk protein in solution, silk solution viscosity, and silk film glass‐transition temperature, and increases the rate of degradation of a silk film by protease. Model compounds spanning a range of physical‐chemical properties generally show an inverse relationship between degumming time and release rate through a varied degumming time silk coating. Degumming provides a useful control point to manipulate silk's material properties.

     

Silk Fibroin-Coated Liposomes as Biomimetic Nanocarrier for Long-Term Release Delivery System in Cancer Therapy

Despite much progress in cancer therapy, conventional chemotherapy can cause poor biodistribution and adverse side-effects on healthy cells. Currently, various strategies are being developed for an effective chemotherapy delivery system. Silk fibroin (SF) is a natural protein used in a wide range of biomedical applications including cancer therapy due to its biocompatibility, biodegradability, and unique mechanical properties. In this study, SF-coated liposomes (SF-LPs) were prepared as a biomimetic drug carrier. Physicochemical properties of SF-LPs were characterized by Fourier-transform infrared spectroscopy (FTIR), dynamic light scattering, zeta potential measurement, and transmission electron microscopy (TEM). In vitro release of SF-LPs loaded with doxorubicin (DOX-SF-LPs) was evaluated over 21 days. Anticancer activity of DOX-SF-LPs was determined against MCF-7 and MDA-MB231 cells using the MTT assay. SF-LPs containing 1% SF exhibited favorable characteristics as a drug carrier. SF coating modified the kinetics of drug release and reduced the cytotoxic effect against L929 fibroblasts as compared to the uncoated liposomes containing cationic lipid. DOX-SF-LPs showed anticancer activity against breast cancer cells after 48 h or 72 h at 20 μM of DOX. This approach provides a potential platform of long-term release that combines biocompatible SF and phospholipids for cancer therapy, achieving efficient drug delivery and reducing side-effects.     

Cyclodextrin-Containing Polymers for Gene Delivery

Cyclodextrin-containing polymers are now being explored as vehicles for delivering nucleic acids into cells. The structures of the cyclodextrin-containing polycations affect the nucleic acid delivery efficiencies and their toxicities. Of interest is the fact that the cyclodextrin-containing polymers reveal lower toxicities than polymers that lack the cyclodextrins. The cyclodextrins endow the nucleic acid delivery vehicles with the ability to be modified by compounds that form inclusion complexes with the cyclodextrins, and these modifications can be performed without disruption of the polymer-nucleic acid interactions. Thus, cyclodextrin-containing polymers provide unique properties for gene delivery.     

Bioreducible cationic random copolymer for gene delivery

Cationic polymers have been widely investigated for gene delivery, although their low transfection efficiency and high cytotoxicity limit their application. We synthesized a bioreducible cationic random copolymer, poly(cystamine bisacylamide‐aminoethyl piperazine)‐co‐poly(cystamine bisacylamide‐histamine) (denoted as CBA‐AEP‐His) from N,N′‐cystamine bis acrylamide (CBA) with aminoethyl piperazine (AEP) and histamine (His). CBA‐AEP‐His copolymer possesses disulfide linkages that endow it with redox‐responsivity to the intracellular environment. This polymer efficiently condenses pZNF580 into complexes with the size of 160 ± 4 nm to 280 ± 5 nm and positive zeta potential of 20 ± 0.3 mV to 30 ± 0.4 mV. The gel‐retardation assay shows that CBA‐AEP‐His can retard pZNF580 even at a low mass ratio of 1/1. The gene complexes were triggered to release pZNF580 when exposed to the reducing environment of dithiothreitol (DTT). CBA‐AEP‐His random copolymer presented higher buffer capacity owing to its His moieties, which protected pZNF580 from DNase degradation. The gene transfection results reveal that CBA‐AEP‐His can efficiently deliver pZNF580 and transfect EA. Hy926 cells. The MTT assay indicates that CBA‐AEP‐His and its complexes exhibit lower cytotoxicity than PEI25KDa. These results illustrate that CBA‐AEP‐His had promising properties for gene delivery, which may provide a suitable platform for the development of a non‐viral gene carrier.     

Switchable Lipids: Conformational Change for Fast pH‐Triggered Cytoplasmic Delivery

We report the use of switchable lipids to improve the endosomal escape and cytosolic delivery of cell‐impermeable compounds. The system is based on a conformational reorganization of the lipid structure upon acidification, as demonstrated by NMR spectroscopic studies. When incorporated in a liposome formulation, the switchable lipids triggered bilayer destabilization through fusion even in the presence of poly(ethylene glycol). We observed 88 % release of sulforhodamine B in 15 min at pH 5, and the liposome formulations demonstrated high stability at pH 7.4 for several months. By using sulforhodamine B as a model of a highly polar drug, we demonstrated fast cytosolic delivery mediated by endosomal escape in HeLa cells, and no toxicity.     

Synthesis of Multivalent Galactosides as Targeting Ligand for Gene Delivery

A series of novel bifunctional glycolipid ligands designed to bind with high affinity and specificity to the asialoglycoprotein receptor (ASGP-R) has been synthesized and assayed in vitro on human hepatoma cells, HepG2, derived from parenchymal liver cells. The compounds bear five β-linked Gal moieties linked to the core scaffold, hexa-antennary alcohol, for interaction with the binding site of the ASGP-R. The liposome/DNA complexes containing the glycolipid ligands are efficiently recognized by ASGP-R and exhibited high affinity and transfection activity.     

Trimethylarsonium-Based Cationic Phospholipids for Gene Delivery

Abstract

Lipophosphoramide-based cationic lipids are a class of synthetic vectors used for gene delivery that can be produced in multigram scale. The use of trimethylarsonium moiety as a cationic polar head was beneficial to produce efficient gene delivery vectors for in vivo applications. Moreover, this type of cationic lipid can also exhibit some bactericidal effects.     

聚天冬酰胺衍生物药物/基因载体的合成和应用

与碳链聚合物相比,聚氨基酸类高分子由于其生物相容性好、可降解代谢、毒副作用低等优点而被广泛应用于生物医药领域。基于天冬氨酸的聚天冬酰胺衍生物,其合成方法简单多样,通过对其修饰改性可制备出具有各种环境响应性（温度、pH和还原敏感）的智能高分子,得到高效、低毒的药物/基因载体,实现可控释放、增强疗效、降低药物副作用的目的。本文重点介绍了聚天冬酰胺衍生物（特别是刺激响应性聚天冬酰胺衍生物）的合成改性方法、及其在药物和基因载体领域最新的研究进展,并对其发展前景进行了展望。     

Optimizing Charge Switching in Membrane Lytic Peptides for Endosomal Release of Biomacromolecules

Endocytic pathways are practical routes for the intracellular delivery of biomacromolecules. Along with this, effective strategies for endosomal cargo release into the cytosol are desired to achieve successful delivery. Focusing on compositional differences between the cell and endosomal membranes and the pH decrease within endosomes, we designed the lipid-sensitive and pH-responsive endosome-lytic peptide HAad. This peptide contains aminoadipic acid (Aad) residues, which serve as a safety catch for preferential permeabilization of endosomal membranes over cell membranes, and His-to-Ala substitutions enhance the endosomolytic activity. The ability of HAad to destabilize endosomal membranes was supported by model studies using large unilamellar vesicles (LUVs) and by increased intracellular delivery of biomacromolecules (including antibodies) into live cells. Cerebral ventricle injection of Cre recombinase with HAad led to Cre/loxP recombination in a mouse model, thus demonstrating potential applicability of HAad in vivo.     

谷胱甘肽响应的非病毒基因传递体系研究

现代基因技术和人类基因组工程图谱的完成,为采用基因分子生物学方法治疗各类疾病,提高人类生命质量开辟了广阔的前景．由于裸DNA分子难以在体液中稳定存在,在主要器官中只能实现低层次的表达,寻求实现广泛基因表达的基因传递系统已成为基因治疗在大规模临床应用中的关键问题,聚乙烯亚胺(PEI)具有“质子海绵”效应,     

Polymeric micelleplexes for improved photothermal endosomal escape and delivery of siRNA

Effective endosomal escape is required for practical application of nucleic acid therapeutics. In this study, we prepared siRNA micelleplexes with photothermally triggered endosomal escape and improved gene silencing activity in vitro. The micelleplexes were prepared from cholesterol‐modified and CXCR4‐inhibiting poly(amido amine)s (PAMD‐Ch). Near‐infrared dye IR780 was encapsulated in cationic PMAD‐Ch micelles, which then were used to form IR780 micelleplexes with siRNA. The micelleplexes displayed improved gene silencing efficiency upon laser irradiation, which was attributed to enhanced endosomal escape because of the photothermal effects of the encapsulated IR780. The IR780 micelleplexes retained the CXCR4 antagonism and inhibition of cancer cell invasion of the parent PAMD. Overall, this study validates codelivery of IR780 in siRNA micelleplexes as promising photothermally controlled siRNA delivery approach.     

Design of Serum Compatible Tetrary Complexes for Gene Delivery

A novel gene delivery system, called PoSC, consisting of PEI, PSP, and HA is described. In contrast to the DNA/PEI/HA ternary system whose transfection efficiency decreases significantly with increasing serum concentration, PoSC exhibits a high transfection efficiency of about 51 and 87% for NIH3T3 and HCT116 cells, respectively, at 50% serum concentration. Furthermore, PoSC shows no cytotoxic effect at its working concentration. The overall results suggest that HA adsorption on cationic complexes enhances the transfection efficiency, while PSP is essential for high transfection efficiency at higher serum concentration.

     

Synthesis of Cholesterylated Thiogalactosides for Gene Delivery

A series of cholesterylated thiogalactosides L₁ –L₆ the cell targeting ligands for gene delivery to hepatocytes, was synthesized. Related poly(ethylene glycol) chain was used as a bridge for the attachment of galactoside on one hydroxyl end, while the other hydroxyl end was linked with cholesterol. This design provided an effective entry for the synthesis of a poly(ethylene glycol) compound with the hepatocyte targeting.     

Glycoconjugated Metallohelices have Improved Nuclear Delivery and Suppress Tumour Growth In Vivo

Monosaccharides are added to the hydrophilic face of a self‐assembled asymmetric Fe^II metallohelix, using CuAAC chemistry. The sixteen resulting architectures are water‐stable and optically pure, and exhibit improved antiproliferative selectivity against colon cancer cells (HCT116 p53^+/+) with respect to the non‐cancerous ARPE‐19 cell line. While the most selective compound is a glucose‐appended enantiomer, its cellular entry is not mainly glucose transporter‐mediated. Glucose conjugation nevertheless increases nuclear delivery ca 2.5‐fold, and a non‐destructive interaction with DNA is indicated. Addition of the glucose units affects the binding orientation of the metallohelix to naked DNA, but does not substantially alter the overall affinity. In a mouse model, the glucose conjugated compound was far better tolerated, and tumour growth delays for the parent compound (2.6 d) were improved to 4.3 d; performance as good as cisplatin but with the advantage of no weight loss in the subjects.