Evaluation of Amphiphilic Star/Linear-Dendritic Polymer Reverse Micelles for Transdermal Drug Delivery: Directing Carrier Properties by Tailoring Core versus Peripheral Branching.

The reverse micelle self-assembly of lipophile-functionalized poly(ethylene glycol) (PEG) dendrimer hybrids is probed for applications in carrier-mediated transdermal drug delivery. Under investigation are topologically diverse amphiphiles featuring controlled branching motifs at either the polymer core (one-, two-, and four-arm PEG) and the polar/nonpolar interface (peripheral dendritic generations 0-2). Thus, a systematic investigation of the effect of branching location (core vs peripheral) on carrier properties is described. Dye-encapsulation experiments verify these materials are capable of forming well-defined aggregates and solubilizing polar compounds. Further quantification of reverse micelle critical micelle concentration and dye loading capacity for the branched amphiphile library was obtained through spectroscopy characterization. Both core and peripheral branching are shown to significantly influence dynamic encapsulation behavior, with evidence of location-based contributions extending beyond multiplicity of branching alone. Finally, the in vitro transdermal diffusion of the reverse micelle carriers was investigated through Franz diffusion cell experiments using physiologically relevant juvenile porcine dermis. The permeation results, combined with previously reported aggregate size trends, show the complex relationship between polymer branching and transdermal transport, with the lowest core- and highest peripherally-branched amphiphilic analogs exhibiting optimal transdermal permeation characteristics for this set of branched carriers.

Synthesis and Self-Assembly of Amphiphilic Star/Linear-Dendritic Polymers: Effect of Core versus Peripheral Branching on Reverse Micelle Aggregation.

A series of branched polymers, consisting of a poly(ethylene glycol) (PEG) core and lipophilic peripheral dendrons, were synthesized and their self-assembly into reverse micelles studied toward the ultimate goal of carrier-mediated transdermal drug delivery. More specifically, this investigation systematically explores the structure-property contributions arising from location and extent of branching by varying the number of branch points at the core and the generation of dendrons at the polar/nonpolar interface. For branching at the core, PEGs were selected with one, two or four arms, with one terminal functionality per arm. For peripheral branching, end groups were modified with polyester dendrons (of dendritic generations 0, 1, and 2) for each of the three cores. Finally, lauric acid (LA) was used to esterify the periphery, yielding a library of branched, amphiphilic polymers. Characterization of these materials via MALDI-TOF MS, GPC and NMR confirmed their exceptionally well-defined structure. Furthermore, atomic force microscopy (AFM) and dynamic light scattering (DLS) confirmed these polymers' abilities to make discrete aggregates. As expected, increased multiplicity of branching resulted in more compact aggregates; however, the location of branching (core vs periphery) did not seem as important in defining aggregate size as the extent of branching. Finally, computational modeling of the branched amphiphile series was explored to elucidate the macromolecular interactions governing self-assembly in these systems.

The Synthesis of Cyclic Poly(ethylene imine) and Exact Linear Analogues: An Evaluation of Gene Delivery Comparing Polymer Architectures.

The delivery of genetic material to cells offers the potential to treat many genetic diseases. Cationic polymers, specifically poly(ethylene imine) (PEI), are promising gene delivery vectors due to their inherent ability to condense genetic material and successfully affect its transfection. However, PEI and many other cationic polymers also exhibit high cytotoxicity. To systematically study the effect of polymer architecture on gene delivery efficiency and cell cytotoxicity, a set of cyclic PEIs were prepared for the first time and compared to a set of linear PEIs of the exact same molecular weight. Subsequent in vitro transfection studies determined a higher transfection efficiency for each cyclic PEI sample when compared to its linear PEI analogue in addition to reduced toxicity relative to the branched PEI "gold standard" control. These results highlight the critical role that the architecture of PEI can play in both optimizing transfection and reducing cell toxicity.

Improved CRISPR genome editing using small highly active and specific engineered RNA-guided nucleases.

Streptococcus pyogenes (Spy) Cas9 has potential as a component of gene therapeutics for incurable diseases. One of its limitations is its large size, which impedes its formulation and delivery in therapeutic applications. Smaller Cas9s are an alternative, but lack robust activity or specificity and frequently recognize longer PAMs. Here, we investigated four uncharacterized, smaller Cas9s and found three employing a "GG" dinucleotide PAM similar to SpyCas9. Protein engineering generated synthetic RNA-guided nucleases (sRGNs) with editing efficiencies and specificities exceeding even SpyCas9 in vitro and in human cell lines on disease-relevant targets. sRGN mRNA lipid nanoparticles displayed manufacturing advantages and high in vivo editing efficiency in the mouse liver. Finally, sRGNs, but not SpyCas9, could be packaged into all-in-one AAV particles with a gRNA and effected robust in vivo editing of non-human primate (NHP) retina photoreceptors. Human gene therapy efforts are expected to benefit from these improved alternatives to existing CRISPR nucleases.