Intrinsic Viscosity of Polymers and Biopolymers Measured by Microchip

Abstract

Intrinsic viscosity provides insight to molecular structure and interactions in solution. A new microchip method is described for fast and accurate measurements of viscosity and intrinsic viscosity of polymer and biopolymer solutions. Polymer samples are diluted with solvent in the microfluidic chip by imposing pressure gradients across the channel network. The concentration and flow dilutions of the polymer sample are calculated from the fluorescent signals recorded over a range of dilutions. The viscosities at various polymer dilutions are evaluated using mass and momentum balances in the pressure-driven microchannel flow. The technique is particularly important to many chemical, biological, and medical applications where sample is available in very small quantities. The intrinsic viscosity experiments were performed for three classes of polymer solutions: (a) poly(ethylene glycol), polymers with linear hydrocarbon chains; (b) bovine serum albumin, biopolymer chains with hydrophobic and hydrophilic amino acids, and (c) DNA fragments, biological macromolecules with double-stranded polymeric chains. The measured values of intrinsic viscosity agree remarkably well with the available data obtained using different methods. The data exhibit power law behavior for molecular weight as described by the Mark-Houwink-Sakurada equation. Experiments were performed to understand the effect of solvent quality and salt concentration on molecular conformations and the intrinsic viscosity of the polymers. This method offers a new way to study the conformational changes in proteins and DNA solutions in various buffer conditions such as pH, ionic strength, and surfactants. The effects of shear rate in the microchannel and mixing time on the accuracy and limitation of the measurement method are discussed.

Microfluidic rheometry

“…(a) imposing a pressure drop and measuring the flow rate (Srivastava et al, 2005;Lee and Tripathi, 2005;Degré et al, 2006;Guillot et al, 2006;Lin et al, 2007;Han et al, 2007;Masselon et al, 2008), and (b) imposing the flow rate and measuring the resulting pressure drop (Kang et al, 2005;Pipe et al, 2008).…”

“…The controlled-pressure microfluidic device of Lee and Tripathi (2005) enables direct measurement of the intrinsic viscosity of biopolymer solutions and the flow rate is evaluated by fluorescence intensity of the bulk flow.…”

The intrinsic viscosity of linear DNA

“…39 Although, in general, it is assumed to be a constant independent of the molecular weight, for various polymers, there is evidence to the contrary. 75 In an effort to see whether the value of K H depends on the length of the DNA chain, we collected data reported in previous studies 40,41,45,47,54,59 as well as the results from our own measurements (see Table I); these are shown in Figure 4. The K H values are more error prone due 828 Tsortos, Papadakis, and Gizeli to the way they are calculated [Eq.…”

Physico-Chemical Studies on the Interaction of Bacterial Polysaccharide- Surfactant Aggregates with Special Reference to their Hydrodynamic Behavior

“…The influence of the two factors may vary depending upon the nature of the SPS. Intrinsic viscosity was measured as it is related to radius of gyration for a dilute polymer solution 50 . At low concentrations, due to ion-ion repulsion the random configuration of the polymer chain opens up resulting in extended structure which leads to increase in viscosity.…”