Combinatorial synthesis of chemically diverse core-shell nanoparticles for intracellular delivery.

Analogous to an assembly line, we employed a modular design for the high-throughput study of 1,536 structurally distinct nanoparticles with cationic cores and variable shells. This enabled elucidation of complexation, internalization, and delivery trends that could only be learned through evaluation of a large library. Using robotic automation, epoxide-functionalized block polymers were combinatorially cross-linked with a diverse library of amines, followed by measurement of molecular weight, diameter, RNA complexation, cellular internalization, and in vitro siRNA and pDNA delivery. Analysis revealed structure-function relationships and beneficial design guidelines, including a higher reactive block weight fraction, stoichiometric equivalence between epoxides and amines, and thin hydrophilic shells. Cross-linkers optimally possessed tertiary dimethylamine or piperazine groups and potential buffering capacity. Covalent cholesterol attachment allowed for transfection in vivo to liver hepatocytes in mice. The ability to tune the chemical nature of the core and shell may afford utility of these materials in additional applications.

Multilayer buildup and biofouling characteristics of PSS-b-PEG containing films.

Thin films exhibiting protein resistance are of interest in diverse areas, ranging from low fouling surfaces in biomedicine to marine applications. Herein, we report the preparation of low protein and cell binding multilayer thin films, formed by the alternate deposition of a block copolymer comprising polystyrene sulfonate and poly(poly(ethylene glycol) methyl ether acrylate) (PSS-b-PEG), and polyallylamine hydrochloride (PAH). Film buildup was followed by quartz crystal microgravimetry (QCM), which showed linear growth and a high degree of hydration of the PSS-b-PEG/PAH films. Protein adsorption studies with bovine serum albumin using QCM demonstrated that multilayer films of PSS/PAH with a terminal layer of PSS-b-PEG were up to 5-fold more protein resistant than PSS-terminated films. Protein binding was dependent on the ionic strength at which the terminal layer of PSS-b-PEG was adsorbed, as well as the pH of the protein solution. It was also possible to control the protein resistance of the films by coadsorption of the final layer with another component (PSS), which showed an increase in protein resistance as the proportion of PSS-b-PEG in the adsorption solution was increased. In addition, protein resistance could also be controlled by the location of a single PSS-b-PEG layer within a PSS/PAH film. Finally, the buildup of PSS-b-PEG/PAH films on colloidal particles was demonstrated. PSS-b-PEG-terminated particles exhibited a 6.5-fold enhancement in cell binding resistance compared with PSS-terminated particles. The stability of PSS-b-PEG films combined with their low protein and cell binding characteristics provide opportunities for the use of the films as low fouling coatings in devices and other surfaces requiring limited interaction with biological interfaces.

Influence of size, surface, cell line, and kinetic properties on the specific binding of A33 antigen-targeted multilayered particles and capsules to colorectal cancer cells.

There has been increased interest in the use of polymer capsules formed by the layer-by-layer (LbL) technique as therapeutic carriers to cancer cells due to their versatility and ease of surface modification. We have investigated the influence of size, surface properties, cell line, and kinetic parameters such as dosage (particle concentration) and incubation time on the specific binding of humanized A33 monoclonal antibody (huA33 mAb)-coated LbL particles and capsules to colorectal cancer cells. HuA33 mAb binds to the A33 antigen present on almost all colorectal cancer cells and has demonstrated great promise in clinical trials as an immunotherapeutic agent for cancer therapy. Flow cytometry experiments showed the cell binding specificity of huA33 mAb-coated particles to be size-dependent, with the optimal size for enhanced selectivity at approximately 500 nm. The specific binding was improved by increasing the dosage of particles incubated with the cells. The level of specific versus nonspecific binding was compared for particles terminated with various polyelectrolytes to examine the surface dependency of antibody attachment and subsequent cell binding ability. The specific binding of huA33 mAb-coated particles is also reported for two colorectal cancer cell lines, with an enhanced binding ratio between 4 and 10 obtained for the huA33 mAb-functionalized particles. This investigation aims to improve the level of specific targeting of LbL particles, which is important in targeted drug and gene delivery applications.