High Strength Bimodal Amphiphilic Conetworks for Immunoisolation Membranes: Synthesis, Characterization, and Properties

Abstract

A strategy for the synthesis of new cross-linkable bimodal amphiphilic grafts (bAPGs) was developed. These grafts are of hydrophilic PDMAAm backbones carrying low (M n ∼ 17 200 g/mol) and high (M n ∼ 117 000 g/mol) molecular weight hydrophobic PDMS branches, each branch carrying a vinylsilyl end-group. The bAPGs were cross-linked by Karstedt catalyst to bimodal amphiphilic conetworks (bAPCNs) by the use of polyhydrosiloxane-co-PDMS as the cross-linker. Membranes prepared from bAPCNs exhibit mechanical properties surprisingly superior to earlier APCNs prepared with APGs with monomodal low molecular weight branches. Membrane bimodality controls surface morphology and topography by means of elastic wrinkling instability during film formation. Semipermeable bAPCN membranes with precisely controlled nanochannel dimensions were prepared so as to allow rapid insulin diffusion and prevent passage of IgG. bAPCN membranes were designed for immunoprotection of live pancreatic islets and are thus key components for a bioartificial pancreas.

Zero‐Order Antibiotic Release from Multilayer Contact Lenses: Nonuniform Drug and Diffusivity Distributions Produce Constant‐Rate Drug Delivery

“…Additionally, the PDMS phase is a bimodal mixture of high and low molecular weight chains, which enhance mechanical properties (and provides us with an extra control dial of functional properties). The synthesis and characterization of β‐APCN was reported . Briefly, the synthesis encompasses free radical terpolymerization of DMAAm with a statistical mixture of low and high molecular weight PDMS, carrying either –vinylsilyl (‐V) or –methacrylate (‐MA) termini (MA‐PDMS‐V, V‐PDMS‐V, and MA‐PDMS‐MA), which yield a slightly cross‐linked bimodal amphiphilic graft (bAPG) consisting of PDMAAm main chains carrying ‐PDMS‐V branches.…”

“…By controlling the molecular weight of the hydrophilic segments and the extent of cross‐linking, the diffusion rate of the drug and its release profiles can be controlled. β‐APCNs are optically clear (see transmission values in Figure C) and possess the mechanical properties for therapeutic contact lenses …”

“…The dimensions of these channels are controlled by the molecular weight between cross‐links ( M c ) of PDMAAm and by morphological thermodynamic/kinetic constrains. M c was calculated bywhere, W PDMAAm and W MA‐PDMS‐V are the weights of PDMAAm and acrylate end‐functionalized PDMS, respectively, M n ,PDMAAm is the number average molecular weight of PDMAAm, whereas M n ,MA‐PDMS‐V is that of acrylate end functionalized PDMS. With calculations based on experimental data, Equation yields M c = 9900 g mol −1 , which represents domains large enough to allow fast moxifloxacin permeation.…”

“…Materials : The synthesis and characterization of β‐APCN was reported . polyhydrosiloxane‐PDMS copolymer (PHMS‐ co ‐PDMS) containing 30% PHMS, and Karstedt's catalyst (3% Pt in xylene, low color) were purchased from Gelest and used without further purification.…”

Recent Trends in Advanced Contact Lenses

“…Continuous hydrophobic phase helps oxygen permeability through lens material and continuous hydrophilic phase provides wettability. The composition and cross‐link density of hydrophilic/hydrophobic phase influence the mechanical properties of the material …”