No abstract

SYNOPSISHigh purity, high molecular weight hyaluronate from bacteria and rooster comb exhibited clear polyelectrolyte properties, as observed by static and dynamic light scattering. The scattered intensity of hyaluronate solutions increased markedly with ionic strength, while the radii of gyration decreased. Apparent persistence lengths within the wormlike chain model in the coil limit were estimated as a function of ionic strength. The total apparent persistence length varied from about 87 8, in the high ionic strength limit to nearly 400 8, at 1 m M added NaC1. The apparent electrostatic persistence length varied approximately as the inverse square root of the ionic strength. Deviations from the theoretically predicted inverse ionic strength dependence were investigated in terms of excluded volume effects. Dynamic light scattering yielded "ordinary phase" diffusion coefficients whose dependence on polymer and salt concentration agreed reasonably well with hydrodynamic coupled mode theory in the linear limit. Extrapolations to infinite polymer dilution at fixed salts yielded, surprisingly, a constant diffusion coefficient. Thus, there was no evidence of either polyion expansion or electrolyte friction effects in the infinite dilution diffusion coefficients. Since clear evidence for polyion expansion was seen in the static scattering, it is thought that the relative stiffness and consequent openness of the hyaluronate coils lead to partial free draining behavior. There was no evidence for an "extraordinary phase" under no added salt and low added salt conditions. The overall results are contrasted with the very different behavior previously reported for medium purity hyaluronate from animal sources.

SYNOPSISThe "extraordinary" diffusional phase ( E P ) at low ionic strength, and the conditions for its removability by filtration were investigated for dilute solutions of the following linear polyelectrolytes: poly ( L-lysine ) , heparin, chondroitin-6-sulfate, hyaluronate, polystyrene sulfonate, and variably ionized polyacrylamide. The E P was not present for all the different types studied, and for heparin, for example, the phase was present only for samples from certain sources. In all cases the phase was removable by filtration through sufficiently small pore-size membranes. Once filtered, the EP remained absent for over one week. It is concluded that the extraordinary diffusional phase consists of fairly stable polyelectrolyte aggregates, and sometimes also includes other very small particulate impurities. These aggregates and other small particles are thought to be present, or at least nascent, in the dry polyelectrolyte material, so that their properties may depend critically on the manner in which such dry material is produced. Tests for "reversibility" of the EP by cycling between high and low C, by dialysis further confirm these conclusions. The evidence is thus against the E P representing any type of temporal aggregates or local ordering, at least for the linear polyelectrolytes studied in this work. Rather, due to the extremely feeble scattering of ordinary polyelectrolytes at low ionic strength, the weak scattering from residual aggregates and other particles, not removed by ordinary filtration and centrifugation procedures, give autocorrelable scattering signals with long decay times. The "loss" of the extraordinary phase as ionic strength increases appears to be due simply to the weak E P scattering signal getting buried in the sharply increasing scattering from the ordinary polyelectrolyte phase. Model calculations based on experimental data support this latter conclusion.

The effects of NaOH on the conformations, interactions, diffusion, and hydrolysis rates of hyaluronate (HA) were characterized in detail using static light scattering (i) in the traditional "batch" mode (for conformations and interactions), (ii) in a time-dependent, simultaneous multiangle mode (for the hydrolysis rates), and (iii) coupled to HPLC for preliminary characterization of distributions of hydrolysis fragments. Strikingly, the conformations, interactions, and hydrolysis rates all seem to be controlled by the titration of the HA hydroxyl groups by NaOH to yield -0", which (i) destroys single strand hydrogen bonds, leading to the very rapid destiffening and contraction of the HA coil and to a large decrease in intermolecular interactions, and (ii) leads to the slow intramolecular cleavage (hydrolysis) of glycosidic bonds. Remarkably, the root mean square radius of gyration Rg, the second virial coefficient A%, and hydrolysis rates all appear as mutually superposing titration curves which yield a pK of around 13. Interestingly, in contrast to classical "nondraining" coil molecules, the hydrodynamic radius of HA, as measured by dynamic light scattering, is independent of [NaOH] and the contraction of Rt.

Designing biologically inspired nanoscale molecular assembly with desired functionality is a challenging endeavour. Here we report the designing of fibrin-inspired nanostructured peptide based sealants which facilitate remarkably fast entrapping of blood corpuscles (~28 seconds) in contrast to fibrin (~56 seconds). Our engineered sealants are stabilized by lysine-aspartate ionic interactions and also by Nε(γ-glutamyl) lysine isopeptide bond mediated covalent interaction. Each sealant is formed by two peptides having complementary charges to promote lysine-aspartate ionic interactions and designed isopeptide bond mediated interactions. Computational analysis reveals the isopeptide bond mediated energetically favourable peptide assemblies in sealants 1–3. Our designed sealants 2 and 3 mimic fibrin-mediated clot formation mechanism in presence of transglutaminase enzyme and blood corpuscles. These fibrin-inspired peptides assemble to form sealants having superior hemostatic activities than fibrin. Designed sealants feature mechanical properties, biocompatibility, biodegradability and high adhesive strength. Such nature-inspired robust sealants might be potentially translated into clinics for facilitating efficient blood clotting to handle traumatic coagulopathy and impaired blood clotting.