Attenuation of Abnormal Scarring Using Spherical Nucleic Acids Targeting Transforming Growth Factor Beta 1.

Abnormal scarring is a consequence of dysregulation in the wound healing process, with limited options for effective and noninvasive therapies. Given the ability of spherical nucleic acids (SNAs) to penetrate skin and regulate gene expression within, we investigated whether gold-core SNAs (AuSNAs) and liposome-core SNAs (LSNAs) bearing antisense oligonucleotides targeting transforming growth factor beta 1 (TGF-ß1) can function as a topical therapy for scarring. Importantly, both SNA constructs appreciably downregulated TGF-ß1 protein expression in primary hypertrophic and keloid scar fibroblasts in vitro. In vivo, topically applied AuSNAs and LSNAs downregulated TGF-ß1 protein expression levels and improved scar histology as determined by the scar elevation index. These data underscore the potential of SNAs as a localized, self-manageable treatment for skin-related diseases and disorders that are driven by increased gene expression.

PLGA Spherical Nucleic Acids.

A new class of polymer spherical nucleic acid (SNA) conjugates comprised of poly(lactic-co-glycolic acid) (PLGA) nanoparticle (NP) cores is reported. The nucleic acid shell that defines the PLGA-SNA exhibits a half-life of more than 2 h in fetal bovine serum. Importantly, the PLGA-SNAs can be utilized to encapsulate a hydrophobic model drug, coumarin 6, which can then be released in a polymer composition-dependent tunable manner, while the dissociation rate of the nucleic acid shell remains relatively constant, regardless of core composition. Like prototypical gold NP conjugate SNAs, PLGA-SNAs freely enter Raw-Blue cells and can be used to activate toll-like receptor 9 in a sequence- and dose-dependent manner. Taken together, the data show that this novel nanoconstruct provides a means for controlling the release kinetics of encapsulated cargos in the context of the SNA platform, which may be useful for developing combination therapeutics.

Retinal conformation governs pKa of protonated Schiff base in rhodopsin activation.

We have explored the relationship between conformational energetics and the protonation state of the Schiff base in retinal, the covalently bound ligand responsible for activating the G protein-coupled receptor rhodopsin, using quantum chemical calculations. Guided by experimental structural determinations and large-scale molecular simulations on this system, we examined rotation about each bond in the retinal polyene chain, for both the protonated and deprotonated states that represent the dark and photoactivated states, respectively. Particular attention was paid to the torsional degrees of freedom that determine the shape of the molecule, and hence its interactions with the protein binding pocket. While most torsional degrees of freedom in retinal are characterized by large energetic barriers that minimize structural fluctuations under physiological temperatures, the C6-C7 dihedral defining the relative orientation of the ß-ionone ring to the polyene chain has both modest barrier heights and a torsional energy surface that changes dramatically with protonation of the Schiff base. This surprising coupling between conformational degrees of freedom and protonation state is further quantified by calculations of the pKa as a function of the C6-C7 dihedral angle. Notably, pKa shifts of greater than two units arise from torsional fluctuations observed in molecular dynamics simulations of the full ligand-protein-membrane system. It follows that fluctuations in the protonation state of the Schiff base occur prior to forming the activated MII state. These new results shed light on important mechanistic aspects of retinal conformational changes that are involved in the activation of rhodopsin in the visual process.