Porous Silicon Nanoparticles Targeted to the Extracellular Matrix for Therapeutic Protein Delivery in Traumatic Brain Injury.

Traumatic brain injury (TBI) is a major cause of disability and death among children and young adults in the United States, yet there are currently no treatments that improve the long-term brain health of patients. One promising therapeutic for TBI is brain-derived neurotrophic factor (BDNF), a protein that promotes neurogenesis and neuron survival. However, outstanding challenges to the systemic delivery of BDNF are its instability in blood, poor transport into the brain, and short half-life in circulation and brain tissue. Here, BDNF is encapsulated into an engineered, biodegradable porous silicon nanoparticle (pSiNP) in order to deliver bioactive BDNF to injured brain tissue after TBI. The pSiNP carrier is modified with the targeting ligand CAQK, a peptide that binds to extracellular matrix components upregulated after TBI. The protein cargo retains bioactivity after release from the pSiNP carrier, and systemic administration of the CAQK-modified pSiNPs results in effective delivery of the protein cargo to injured brain regions in a mouse model of TBI. When administered after injury, the CAQK-targeted pSiNP delivery system for BDNF reduces lesion volumes compared to free BDNF, supporting the hypothesis that pSiNPs mediate therapeutic protein delivery after systemic administration to improve outcomes in TBI.

Microphthalmia and disrupted retinal development due to a LacZ knock-in/knock-out allele at the Vsx2 locus.

Visual System Homeobox 2 (Vsx2) is a transcription factor expressed in the developing retina that regulates tissue identity, growth, and fate determination. Several mutations in the Vsx2 gene exist in mice, including a spontaneous nonsense mutation and two targeted missense mutations originally identified in humans. Here, we expand the genetic repertoire to include a LacZ reporter allele (Vsx2 LacZ ) designed to express beta-Galactosidase (b-GAL) and simultaneously disrupt Vsx2 function (knock-in/knock-out). The retinal expression pattern of b-GAL is concordant with VSX2, and the mutant allele is recessive. Vsx2 LacZ homozygous mice have congenital bilateral microphthalmia accompanied by defects in retinal development including ectopic expression of non-retinal genes, reduced proliferation, delayed neurogenesis, aberrant tissue morphology, and an absence of bipolar interneurons - all hallmarks of Vsx2 loss-of-function. Unexpectedly, the mutant VSX2 protein is stably expressed, and there are subtle differences in eye size and early retinal neurogenesis when compared to the null mutant, ocular retardation J. We propose that b-GAL expression from the Vsx2 LacZ allele is a reliable reporter of VSX2 expression and that the allele exhibits loss-of-function characteristics. However, the perdurance of the mutant VSX2 protein combined with subtle deviations from the null phenotype leaves open the possibility that Vsx2 LacZ allele is not a complete knock-out. The Vsx2 LacZ allele adds to the genetic toolkit for understanding Vsx2 function.

Pharmacokinetic Analysis of Peptide-Modified Nanoparticles with Engineered Physicochemical Properties in a Mouse Model of Traumatic Brain Injury.

Peptides are used to control the pharmacokinetic profiles of nanoparticles due to their ability to influence tissue accumulation and cellular interactions. However, beyond the study of specific peptides, there is a lack of understanding of how peptide physicochemical properties affect nanoparticle pharmacokinetics, particularly in the context of traumatic brain injury (TBI). We engineered nanoparticle surfaces with peptides that possess a range of physicochemical properties and evaluated their distribution after two routes of administration: direct injection into a healthy mouse brain and systemic delivery in a mouse model of TBI. In both administration routes, we found that peptide-modified nanoparticle pharmacokinetics were influenced by the charge characteristics of the peptide. When peptide-modified nanoparticles are delivered directly into the brain, nanoparticles modified with positively charged peptides displayed restricted distribution from the injection site compared to nanoparticles modified with neutral, zwitterionic, or negatively charged peptides. After intravenous administration in a TBI mouse model, positively charged peptide-modified nanoparticles accumulated more in off-target organs, including the heart, lung, and kidneys, than zwitterionic, neutral, or negatively charged peptide-modified nanoparticles. The increase in off-target organ accumulation of positively charged peptide-modified nanoparticles was concomitant with a relative decrease in accumulation in the injured brain compared to zwitterionic, neutral, or negatively charged peptide-modified nanoparticles. Understanding how nanoparticle pharmacokinetics are influenced by the physicochemical properties of peptides presented on the nanoparticle surface is relevant to the development of nanoparticle-based TBI therapeutics and broadly applicable to nanotherapeutic design, including synthetic nanoparticles and viruses.