A low cost point-of-care viscous sample preparation device for molecular diagnosis in the developing world; an example of microfluidic origami.

The lab-on-a-chip concept has led to several point-of-care (POC) diagnostic microfluidic platforms. However, few of these can process raw samples for molecular diagnosis and fewer yet are suited for use in a resource-limited setting without permanent electrical infrastructure. We present here a very low cost paper microfluidic device for POC extraction of bacterial DNA from raw viscous samples--a challenge for conventional microfluidic platforms. This is an example of "microfluidic origami" in that the system is activated by folding; demonstrated here is room temperature cell lysis and DNA extraction from pig mucin (simulating sputum) spiked with E. coli without the use of external power. The microfluidic origami device features dry reagent storage and rehydration of the lysis buffer. We demonstrate DNA extraction from samples with a bacterial load as low as 33 CFU ml(-1). Extraction times, starting from the raw sample, have been optimized to about 1.5 h without the use of external power, or to within 1 h using an oven or a heater block. The fabrication of this paper microfluidic device can be translated into high volume production in the developing world without the need for a semiconductor clean room or a microfabrication facility. The sample preparation can be performed with the addition of just the sample, water, ethanol and elute buffer to the device, thus reducing chemical hazards during transport and handling.

[Infectious endocarditis of the heart valves and valvular prostheses. report of 21 cases]. / Endocarditis infecciosa de válvulas cardíacas y prótesis valvulares. reporte de 21 casos.

During 1978, and 1979, the Surgery Division of The Cardiology and Pneumology Hospital of The National Medical Center (Mexican Institute for Social Security), studied and treated surgically twenty one cases -- in twenty patients -- of infectious endocarditis. Nine patients had an active infection in the heart valves and twelve in the prosthesis. The survival rate of the first group was 88.88% and of the second group 58.33%. The causes of death were due to the hemodynamic damage that the valvular or prosthetic dysfunction leads to, when there is a delay in the arrival of the patient to a medical unit of third level. The conventional medical treatment applicable to a reduced number of cases whose characteristics are discussed do not operate when dealing with patients with infected prosthesis or valve infections caused by non-gram positive bacteria. We conclude that this problem demands a better approach, principally surgical, to improve the prognosis of these patients.