Zwitterionic peptides: Tunable next-generation stealth nanoparticle modifications.

Adsorption of proteins to nanoparticles (NPs), a complex process that results in a protein corona, is controlled by NP surface properties that define NP interactions in vivo. Efforts to control adsorbed protein quantity through surface modification have led to improvements in circulation time or biodistribution. Still, current approaches have yet to be identified to control adsorbed protein identities within the corona. Here, we report the development and characterization of diverse zwitterionic peptides (ZIPs) for NP anti-fouling surface functionalization with specific and controllable affinity for protein adsorption profiles defined by ZIP sequence. Through serum exposure of ZIP-conjugated NPs and proteomics analysis of the resulting corona, we determined that protein adsorption profiles depend not on the exact composition of the ZIPs but on the sequence and order of charges along the sequence (charge motif). These findings pave the way for developing tunable ZIPs to orchestrate specific ZIP-NP protein adsorption profiles as a function of ZIP charge motif to better control cell and tissue specificity and pharmacokinetics and provide new tools for investigating relationships between protein corona and biological function. Furthermore, overall ZIP diversity enabled by the diversity of amino acids may ameliorate adaptive immune responses.

Impact of Nanoparticle Physicochemical Properties on Protein Corona and Macrophage Polarization.

Macrophages, the major component of the mononuclear phagocyte system, uptake and clear systemically administered nanoparticles (NPs). Therefore, leveraging macrophages as a druggable target may be advantageous to enhance NP-mediated drug delivery. Despite many studies focused on NP-cell interactions, NP-mediated macrophage polarization mechanisms are still poorly understood. This work aimed to explore the effect of NP physicochemical parameters (size and charge) on macrophage polarization. Upon exposure to biological fluids, proteins rapidly adsorb to NPs and form protein coronas. To this end, we hypothesized that NP protein coronas govern NP-macrophage interactions, uptake, and subsequent macrophage polarization. To test this hypothesis, model polystyrene NPs with various charges and sizes, as well as NPs relevant to drug delivery, were utilized. Data suggest that cationic NPs potentiate both M1 and M2 macrophage markers, while anionic NPs promote M1-to-M2 polarization. Additionally, anionic polystyrene nanoparticles (APNs) of 50 nm exhibit the greatest influence on M2 polarization. Proteomics was pursued to further understand the effect of NPs physicochemical parameters on protein corona, which revealed unique protein patterns based on NP charge and size. Several proteins impacting M1 and M2 macrophage polarization were identified within cationic polystyrene nanoparticles (CPNs) corona, while APNs corona included fewer M1 but more M2-promoting proteins. Nevertheless, size impacts protein corona abundance but not identities. Altogether, protein corona identities varied based on NP surface charge and correlated to dramatic differences in macrophage polarization. In contrast, NP size differentially impacts macrophage polarization, which is dominated by NP uptake level rather than protein corona. In this work, specific corona proteins were identified as a function of NP physicochemical properties. These proteins are correlated to specific macrophage polarization programs and may provide design principles for developing macrophage-mediated NP drug delivery systems.

Biomaterials for Orthopaedic Diagnostics and Theranostics.

Despite widespread use of conventional diagnostic methods in orthopaedic applications, limitations still exist in detection and diagnosing many pathologies especially at early stages when intervention is most critical. The use of biomaterials to develop diagnostics and theranostics, including nanoparticles and scaffolds for systemic or local applications, has significant promise to address these shortcomings and enable successful clinical translation. These developments in both modular and holistic design of diagnostic and theranostic biomaterials may improve patient treatments for myriad orthopaedic applications ranging from cancer to fractures to infection.

Delivery of RNAi-Based Therapeutics for Bone Regeneration.

PURPOSE OF REVIEW: The clinical significance, target pathways, recent successes, and challenges that preclude translation of RNAi bone regenerative approaches are overviewed. RECENT FINDINGS: RNA interference (RNAi) is a promising new therapeutic approach for bone regeneration by stimulating or inhibiting critical signaling pathways. However, RNAi suffers from significant delivery challenges. These challenges include avoiding nuclease degradation, achieving bone tissue targeting, and reaching the cytoplasm for mRNA inhibition. Many drug delivery systems have overcome stability and intracellular localization challenges but suffer from protein adsorption that results in clearance of up to 99% of injected dosages, thus severely limiting drug delivery efficacy. While RNAi has myriad promising attributes for use in bone regenerative applications, delivery challenges continue to plague translation. Thus, a focus on drug delivery system development is critical to provide greater delivery efficiency and bone targeting to reap the promise of RNAi.

Rigor and reproducibility in polymer nanoparticle synthesis and characterization.

Standardized process improvement methods and tools were used to enhance the rigor and reproducibility of diblock copolymer nanoparticle (NP) synthesis and characterization. Models linking design parameters with NP characteristics boosted process control for NP synthesis, which may improve translation and commercialization of NP research.

An in vitro platform for elucidating the molecular genetics of S. aureus invasion of the osteocyte lacuno-canalicular network during chronic osteomyelitis.

Staphylococcus aureus osteomyelitis is a devasting disease that often leads to amputation. Recent findings have shown that S. aureus is capable of invading the osteocyte lacuno-canalicular network (OLCN) of cortical bone during chronic osteomyelitis. Normally a 1 µm non-motile cocci, S. aureus deforms smaller than 0.5 µm in the sub-micron channels of the OLCN. Here we present the µSiM-CA (Microfluidic - Silicon Membrane - Canalicular Array) as an in vitro screening platform for the genetic mechanisms of S. aureus invasion. The µSiM-CA platform features an ultrathin silicon membrane with defined pores that mimic the openings of canaliculi. While we anticipated that S. aureus lacking the accessory gene regulator (agr) quorum-sensing system would not be capable of invading the OLCN, we found no differences in propagation compared to wild type in the µSiM-CA. However the µSiM-CA proved predictive as we also found that the agr mutant strain invaded the OLCN of murine tibiae.