Design and facile solid-phase synthesis of peptide-based LPS-inhibitors containing PEG-like functionalities

In Vitro and In Vivo Assessment of PEGylated PEI for Anti-IL-8/CxCL-1 siRNA Delivery to the Lungs

Inhalation offers a means of rapid, local delivery of siRNA to treat a range of autoimmune or inflammatory respiratory conditions. This work investigated the potential of a linear 10 kDa Poly(ethylene glycol) (PEG)-modified 25 kDa branched polyethyleneimine (PEI) (PEI-LPEG) to effectively deliver siRNA to airway epithelial cells. Following optimization with anti- glyceraldehyde 3-phosphate dehydrogenase (GAPDH) siRNA, PEI and PEI-LPEG anti-IL8 siRNA nanoparticles were assessed for efficacy using polarised Calu-3 human airway epithelial cells and a twin stage impinger (TSI) in vitro lung model. Studies were then advanced to an in vivo lipopolysaccharide (LPS)-stimulated rodent model of inflammation. In parallel, the suitability of the siRNA-loaded nanoparticles for nebulization using a vibrating mesh nebuliser was assessed. The siRNA nanoparticles were nebulised using an Aerogen^® Pro vibrating mesh nebuliser and characterised for aerosol output, droplet size and fine particle fraction. Only PEI anti-IL8 siRNA nanoparticles were capable of significant levels of IL-8 knockdown in vitro in non-nebulised samples. However, on nebulization through a TSI, only PEI-PEG siRNA nanoparticles demonstrated significant decreases in gene and protein expression in polarised Calu-3 cells. In vivo, both anti-CXCL-1 (rat IL-8 homologue) nanoparticles demonstrated a decreased CXCL-1 gene expression in lung tissue, but this was non-significant. However, PEI anti-CXCL-1 siRNA-treated rats were found to have significantly less infiltrating macrophages in their bronchoalveolar lavage (BAL) fluid. Overall, the in vivo gene and protein inhibition findings indicated a result more reminiscent of the in vitro bolus delivery rather than the in vitro nebulization data. This work demonstrates the potential of nebulised PEI-PEG siRNA nanoparticles in modulating pulmonary inflammation and highlights the need to move towards more relevant in vitro and in vivo models for respiratory drug development.

Self-assembly of bioactive peptides, peptide conjugates, and peptide mimetic materials

Molecular self-assembly is a multi-disciplinary field of research, with potential chemical and biological applications. One of the main driving forces of self-assembly is molecular amphiphilicity, which can drive formation of complex and stable nanostructures. Self-assembling peptide and peptide conjugates have attracted great attention due to their biocompatibility, biodegradability and biofunctionality. Understanding assembly enables the better design of peptide amphiphiles which may form useful and functional nanostructures. This review covers self-assembly of amphiphilic peptides and peptide mimetic materials, as well as their potential applications.

Novel peptide-based platform for the dual presentation of biologically active peptide motifs on biomaterials

Biofunctionalization of metallic materials with cell adhesive molecules derived from the extracellular matrix is a feasible approach to improve cell-material interactions and enhance the biointegration of implant materials (e.g., osseointegration of bone implants). However, classical biomimetic strategies may prove insufficient to elicit complex and multiple biological signals required in the processes of tissue regeneration. Thus, newer strategies are focusing on installing multifunctionality on biomaterials. In this work, we introduce a novel peptide-based divalent platform with the capacity to simultaneously present distinct bioactive peptide motifs in a chemically controlled fashion. As a proof of concept, the integrin-binding sequences RGD and PHSRN were selected and introduced in the platform. The biofunctionalization of titanium with this platform showed a positive trend towards increased numbers of cell attachment, and statistically higher values of spreading and proliferation of osteoblast-like cells compared to control noncoated samples. Moreover, it displayed statistically comparable or improved cell responses compared to samples coated with the single peptides or with an equimolar mixture of the two motifs. Osteoblast-like cells produced higher levels of alkaline phosphatase on surfaces functionalized with the platform than on control titanium; however, these values were not statistically significant. This study demonstrates that these peptidic structures are versatile tools to convey multiple biofunctionality to biomaterials in a chemically defined manner.

Trivalent PEGylated platform for the conjugation of bioactive compounds

PEGylated multivalent structures are a new class of platform for biological applications due to their biocompatibility properties. Here, we present the synthesis of a trivalent structure 1 based on poly(ethylene glycol) units (PEG) as potential synthetic multifunctional carrier molecule. To evaluate whether this PEGylated platform could be useful for the conjugation of bioactive compounds, a well-known lipopolysaccharide (LPS) inhibitor 2, developed in our laboratory, was selected to be conjugated to 1. The LPS-neutralizing activity of the resulted conjugates and precursors was established using the chromogenic Limulus amebocyte lysate (LAL) assay. The trivalent structure 1 did not show LPS-binding activity, nonconjugate LPS inhibitor 2 showed high LPS-neutralizing activity, and the trivalent conjugate 4 displayed increased LPS-neutralizing activity and a reduced toxicity profile. These results prove the efficacy of this trivalent platform as a multivalent ligand scaffold for biological applications.