Zeolite A and calcium phosphate modified Zeolite A have been shown to be a new effective packing material in ion exchange chromatography for the purification of immunoglobulin G (IgG) from binary mixtures and mouse ascites fluid. This study was to determine the effectiveness of purifying IgG using Zeolite X and dealuminated Zeolite X with twice the pore size of Zeolite A. Binary mixtures (IgG-albumin and IgG-transferrin) and a mouse ascites fluid were purified in Zeolite X (in Na+, K+, or NH4+ form) chromatographic columns and with dealuminated Zeolite X under a variety of operational conditions. The biological activity of the purified IgG from the mouse ascites fluid was confirmed by ELISA. The characteristics of zeolites in the present study suggest that functional groups of a protein displace the cations of zeolites near the crystal surfaces and create a different strength of affinity. The study demonstrated that Zeolite X and dealuminated Zeolite X are also promising new packing materials for the purification of IgG from biological materials.

Albumins↗

PubMedDate not supplied

Pressure-volume relationship of a pulsatile blood pump for ventricular assist device development.

A mathematical model describing the pressure-volume relationship of the Novacor left ventricular assist system (LVAS) was developed. The model consists of lumped resistance, capacitance, and inductance elements with one time varying capacitor to estimate the cyclic pressure generation of the pump using pump volume measurement. The ejection and filling portions of the pump cycle were modeled with two separate functions. The corresponding model parameters were estimated by least squares fit to experimental data obtained in the laboratory. Pressure and volume waveforms obtained from the model were compared with data obtained from laboratory tests and from patients. It performed well in simulating pump operation throughout the entire cycle. This model can be used for the evaluation of LVAS performance, for on-line estimation of an LVAS patient's cardiovascular parameters, for pump controller development, and as a tool for engineer training.

Heart-Assist Devices↗

PubMedDate not supplied

Controller for an axial-flow blood pump.

An axial-flow ventricular assist device (VAD) under development at the authors' facility is intended for use as a long-term implantable device. At high speeds axial-flow VADs can collapse the native ventricle and damage the heart muscle, lung tissue, and blood. A prototype algorithm was developed to maintain physiologic perfusion to the vital organs while preventing ventricular collapse, through analysis of the electrical current waveform of the motor. The premise of the control algorithm is that the hemodynamics of the patient are reflected in the shape of this waveform. This approach is intended to eliminate the need for invasive sensors, thus effectively using the pump itself as a transducer. The control algorithm regulates the speed of the pump by comparing the motor-current waveform with reference waveforms using a matched filter. The matched filter was evaluated by its classification and differentiation performance. Thus far, the authors have been able to classify the waveforms into one of the four physiologic regions (below, within, or above the optimal range, and ventricular suction) with over 90% reliability. Ongoing work is directed toward improving the detection of ventricular suction, as this condition must be strictly avoided.

Algorithms↗