Self-Immolative Polyurethane-Based Nanoassemblies: Surface Charge Modulation at Tumor-Relevant pH and Redox-Responsive Guest Release.

The self-assembly of a stimuli-responsive amphiphilic polymer has been of great interest in the area of targeted drug delivery applications. In this article, a new amphiphilic polyurethane with a hydrophobic backbone consisting of a redox-responsive self-immolative unit and hydrophilic pendant triethylene glycol, which is periodically grafted on the backbone by a tertiary amine group, has been designed and synthesized. This amphiphilic polymer self-assembles into a micellar nanostructure (investigated by dynamic light scattering and transmission electron microscopy) in an aqueous medium and shows guest encapsulation property. Furthermore, the pH-responsive nature leads to the formation of a positively charged nanoassembly at a tumor-relevant pH (∼6.5-6.8), which is probed by zeta potential measurements. As the backbone was constructed with self-immolative, redox-responsive functionality, degradation of the polymer was observed in the presence of a reducing agent, glutathione (GSH), which results in disassembly of the self-assembled structure followed by guest release as probed by UV-vis spectroscopy. The triggered degradation and pH-specific charge generation (from neutral to positive), we believe, will have implications in the design of biodegradable polymers as supramoleular scaffolds for biomedical applications.

Combinatorial Synthesis of a Lipidoid Library by Thiolactone Chemistry: In Vitro Screening and In Vivo Validation for siRNA Delivery.

Transcriptional inhibition by small interfering RNA (siRNA) delivery using synthetic transfection agents eliminates the subsequent risk of introducing mutations in relevant genes, as opposed to viral vectors. However, synthetic vectors with comparable transfection efficiency to that of viral vectors are yet to be developed. Hence, synthesizing new transfection vehicles with low toxicity is important. In this study, a library of lipid-like molecules (lipidoids) was synthesized by thiolactone chemistry. This library facilitated nonviral delivery of siRNA to mammalian cells, inducing sequence-specific knockdown of a target gene. The liposomal nanoparticles complexed with anti-green fluorescent protein (GFP) siRNA were successfully screened for transfection efficiency using a HeLa-GFP cell line. The five best-performing lipidoids identified in the screening were found to exhibit superior GFP-knockdown efficiency compared with commercially available transfection reagents. The efficiency of siRNA delivery by one of these lipidoids with minimal toxicity was further successfully evaluated in vivo using Kdrl:EGFP zebrafish embryos as a model system. Our study would be important as a facile synthetic route of efficient nonviral nucleic acid delivery to live cells and organisms.

Author Correction: Marrying chemistry with biology by combining on-chip solution-based combinatorial synthesis and cellular screening.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Marrying chemistry with biology by combining on-chip solution-based combinatorial synthesis and cellular screening.

Drug development often relies on high-throughput cell-based screening of large compound libraries. However, the lack of miniaturized and parallelized methodologies in chemistry as well as strict separation and incompatibility of the synthesis of bioactive compounds from their biological screenings makes this process expensive and inefficient. Here, we demonstrate an on-chip platform that combines solution-based synthesis of compound libraries with high-throughput biological screenings (chemBIOS). The chemBIOS platform is compatible with both organic solvents required for the synthesis and aqueous solutions necessary for biological screenings. We use the chemBIOS platform to perform 75 parallel, three-component reactions to synthesize a library of lipidoids, followed by characterization via MALDI-MS, on-chip formation of lipoplexes, and on-chip cell screening. The entire process from the library synthesis to cell screening takes only 3 days and about 1 mL of total solutions, demonstrating the potential of the chemBIOS technology to increase efficiency and accelerate screenings and drug development.

Programmed supramolecular nanoassemblies: enhanced serum stability and cell specific triggered release of anti-cancer drugs.

A bolaamphiphilic cross-linked nanoassembly endowed with pH responsive degradation features has been designed and fabricated for stable noncovalent guest encapsulation and controlled release. The self-assembled bolaamphiphile is utilized to prepare cross-linked nanoassemblies to further stabilize the noncovalent guest encapsulation at a concentration below its critical aggregation concentration (CAC) in a large volume of water or serum for drug delivery applications. Thus, this system can simultaneously address premature drug release and safety issues. The nanoassemblies integrated with a ß-thioester linker, which can be hydrolyzed selectively under mildly acidic conditions (pH ∼ 5.3) at a slow rate, thus enable controlled release of guest molecules. Biological evaluation revealed that doxorubicin loaded cross-linked nanoassemblies (CNs-DOX) are nontoxic to normal cells such as HEK-293 or PBMC, but in contrast, showed a robust apoptotic effect on colon cancer cells, HCT-116, indicating excellent specificity. Thus, the fabrication reproducibility, robust stability, triggered drug release and cell selective toxicity behavior make this small molecular system very promising in the field of chemotherapeutic applications.

One-Pot Parallel Synthesis of Lipid Library via Thiolactone Ring Opening and Screening for Gene Delivery.

Efficient delivery of nucleic acids into cells is of great interest in the field of cell biology and gene therapy. Despite a lot of research, transfection efficiency and structural diversity of gene-delivery vectors are still limited. A better understanding of the structure-function relationship of gene delivery vectors is also essential for the design of novel and intelligent delivery vectors, efficient in "difficult-to-transfect" cells and in vivo clinical applications. Most of the existing strategies for the synthesis of gene-delivery vectors require multiple steps and lengthy procedures. Here, we demonstrate a facile, three-component one-pot synthesis of a combinatorial library of 288 structurally diverse lipid-like molecules termed "lipidoids" via a thiolactone ring opening reaction. This strategy introduces the possibility to synthesize lipidoids with hydrophobic tails containing both unsaturated bonds and reducible disulfide groups. The whole synthesis and purification are convenient, extremely fast, and can be accomplished within a few hours. Screening of the produced lipidoids using HEK293T cells without addition of helper lipids resulted in identification of highly stable liposomes demonstrating ∼95% transfection efficiency with low toxicity.