High levels of serum low-density lipoprotein (LDL) cholesterol contribute to atherosclerosis, a key risk factor of cardiovascular diseases. PCSK9 is a circulatory enzyme that downregulates expression of hepatic LDL receptors, concomitantly increasing serum LDL-C. This work investigates a small, self-assembling peptide, EPep2-8, as a peptide inhibitor of PCSK9. EPep2-8 is a multidomain peptide comprising a self-assembling domain, E2, conjugated to a bioactive domain, Pep2-8, previously shown to inhibit PCSK9. The E2 domain facilitates self-assembly of EPep2-8 into long, nanofibrous polymers with an underlying supramolecular β-sheet secondary structure. Intermolecular interactions between nanofibers drive EPep2-8 to form a thixotropic and cytocompatible hydrogel in aqueous and charge-neutral solutions. These properties enable EPep2-8 to be delivered as an in situ depot for regulation of lipoprotein homeostasis. In surface plasmon resonance studies, EPep2-8 bound specifically to PCSK9 with an apparent, noncovalent, and irreversible dissociation, significantly improving the binding affinity of Pep2-8 alone (K D = 667 ± 48 nM). Increased binding affinity of EPep2-8 is primarily due to the superstoichiometric interaction of the peptide with PCSK9. Promisingly, EPep2-8 retains bioactivity in vitro, engendering dose-dependent uptake of LDL-C in hepatocytes. This mechanism of self-assembly on a target site may be a simple method to improve the affinity of peptide inhibitors.

Microfluidic devices are constructed from polydimethylsiloxane (PDMS) due to their biocompatibility, fabrication ease, well-established protocols, and simplicity. PDMS-based microfluidic devices are constructed by (i) applying liquid PDMS to a negative mold (usually a silicon or 3D-printed mold) and (ii) curing the PDMS with heat exposure over a set time period. Unreacted resin monomers in 3D-printed molds prevent PDMS from fully curing, resulting in improper channel formation in PDMS and reducing the PDMS device’s efficacy. An in-house protocol that uses SU-8 as a “non-stick” coating on 3D-printed molds facilitates the successful casting of PDMS. Contact angle, surface profile, optical profile, and force testing prove that PDMS cast from SU-8-treated molds resembles pristine PDMS, unlike PDMS cast from untreated molds. Further, this method is generalized to commercial 3D prints using different 3D printing resins. To demonstrate this technique’s viability in microfluidic devices, a microfluidic tree using PDMS from treated 3D prints shows vibrant colors and clear lines. This is absent from an untreated PDMS.

The opioid epidemic in the United States is a serious public health crisis affecting over 1.7 million Americans. In the last two decades, almost 450 000 people have died from an opioid overdose, with nearly 20% of these deaths occurring in 2017 and 2018 alone. During an overdose, overstimulation of the μopioid receptor leads to severe and potentially fatal respiratory depression. Naloxone is a competitive μ-opioid-receptor antagonist that is widely used to displace opioids and rescue from an overdose. Here, we describe the development of a slow-release, subcutaneous naloxone formulation for potential management of opioid overdose, chronic pain, and opioid-induced constipation. Naloxone is loaded into self-assembling peptide hydrogels for controlled drug release. The mechanical, chemical, and structural properties of the nanofibrous hydrogel enable subcutaneous administration and slow, diffusion-based release kinetics of naloxone over 30 days in vitro. The naloxone hydrogel scaffold showed cytocompatibility and did not alter the β-sheet secondary structure or thixotropic properties characteristic of self-assembling peptide hydrogels. Our results show that this biocompatible and injectable self-assembling peptide hydrogel may be useful as a vehicle for tunable, sustained release of therapeutic naloxone. This therapy may be particularly suited for preventing renarcotization in patients who refuse additional medical assistance following an overdose.

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