*** HIGH PRECISION AT LOW COST ***

Vilastic Scientific presents the BioProfiler, the only rheometer dedicated to measurements of blood viscoelasticity and plasma viscosity with the sensitivity beyond the capability of conventional rotational rheometers. By measuring both the viscosity and elasticity, the BioProfiler gives physiologically significant characterization of the dynamic flow properties of blood*.

The BioProfiler fulfills the critical demands of hemorheology with:

• Measurements performed near the pulse rate
• Precise vessel-like geometery
• Simple sample handling and rapid measurements
• Small sample sizes of 0.5 ml to 1.0 ml
• Operating temperatures from 10 °C to 40
• Automated data analysis
• Standardized measurement protocols
• Portability

making it the first choice for advanced research.

Because blood flow in the circulation is pulsatile, the heart pumps energy into the blood with each beat. Portions of this energy are either dissipated or stored as the blood cells rearrange, orient and deform in order to pass through the circulation. Viscosity is an assessment of the rate of energy dissipation due to cell deformation and sliding. Elasticity is an assessment of the elastic storage of energy primarily in the kinetic deformability of the red blood cells. Together, the viscosity and elasticity determine the pressure required to produce blood flow.

The relative influence of aggregation tendency and kinetic elastic cell deformability on blood viscoelasticity changes with shear rate (see our Tech Note). The viscosity and elasticity of blood are direct indicators of how these parameters affect the ability of the blood to flow under the shear conditions imposed by the pulsatility of the circulation. Therefore, in order to provide a complete picture of hemorheology, the BioProfiler measures the viscoelasticity for oscillatory flow over a range of shear rates.

Shear Rate Sweep Protocol for Comprehensive Characterization

Critical Three Point Protocol for Simple and Rapid Characterization

These protocols are governed by Vilatic Software, which controls the timing of flow activation and measurement in order to stabilize the effects of thixotopy.   All measured values undergo complete analysis to give values of the viscosity and elasticity as well as the relaxation time of the blood structure.

SHEAR RATE SWEEP PROTOCOL

The Shear Rate Sweep Protocol automatically measures the viscosity and elasticity of blood at a frequency of 2 Hz over a range of shear rates. The timing of each measurement is precisely controlled so that conditions can be duplicated.  Plots of viscosity and elasticity versus shear rate give a profile of the viscoelasticity of the blood in varying structural states. Optional plots of shear stress and relaxation time versus strain or shear rate are also available.  The ASCII output option exports data from several samples into one file, which is compatible with most spreadsheet programs.

The viscoelastic profile produced by the Shear Rate Sweep Protocol characterizes the changes in viscosity and elasticity due to the alteration of the arrangement, orientation and stretching of the red blood cells in shear.  The viscoelastic profile of normal human blood can be divided into three regions: Low-Shear Region, Mid-Shear Region and High-Shear Region.

Low-Shear Region

Here the aggregation tendency of the red cells has its full effect in producing large clusters. As the shear rate increases the shear stress begins to produce some disaggregation and overall reduces the size of aggregates. Cell deformability also affects the character of the aggregates. In this region the character of the aggregates dominates the viscoelasticity.

Mid-Shear Region

Cell aggregates are largely destroyed by the stress levels present at these shear rates. Shear flow demands that red cells orient and deform in order to pass adjacent cells. In this region the influence of aggregation on viscoelasticity sharply diminishes and the relative influence of cell deformability begins to increase.

The red cells are strongly aligned to form layers that slide on adjacent plasma layers. The viscoelasticity is strongly influenced by cell deformability because this property limits the ability of the cell to conform to layers. Less deformable cells form thicker cell layers with thinner plasma layers, thus increasing both viscosity and elasticity.

The Critical Three Point Protocol simplifies the viscoelastic profile using three rapid measurements at fixed strains in the low, mid and high shear region.  By sampling the viscoelastic properties of the blood in each region, simple numberical characterization of the effects of aggregation and dynamic deformability can be used for statistical studies and montiroing progressive hemorheological changes.  These critical measurements are automatically tabulated at the native hematocrit and projected to a hematocrit of 45%, with temperature projections to 25 °C and 37 °C.   The ASCII output option exports data from several samples into one file, which is compatible with most spreadsheet programs. 

The same precision and reproducibility that makes the BioProfiler ideal for blood viscoelasticity measurements makes it the perfect tool for the measurement of plasma viscosity. With the Vilastic software, quick and simple measurements of plasma viscosity are made, displayed and printed. Viscosity values are provided at the temperature of measurement and automatically projected to 25 °C and 37 °C. The ASCII output option exports data from several samples into one file, which is compatible with most spreadsheet programs.

To learn more about how the BioProfiler technology is suited to blood visit Challenges of Blood.