ABSTRACT
Point-of-care (PoC) diagnostics for bacterial detection offer tremendous prospects for public health care improvement. However, such tools require the complex combination of the following performances: rapidity, selectivity, sensitivity, miniaturization and affordability. To meet these specifications, this paper presents a new selectivity method involving lysostaphin together with a CMOS-compatible impedance sensor for genus-specific bacterial detection. The method enables the sample matrix to be directly flown on the polydopamine-covered sensor surface without any pre-treatment, and considerably reduces the background noise. Experimental proof-of-concept, explored by simulations and confirmed through a setup combining simultaneous optical and electrical real-time monitoring, illustrates the selective and capacitive detection of Staphylococcus epidermidis in synthetic urine also containing Enterococcus faecium. While providing capabilities for miniaturization and system integration thanks to CMOS compatibility, the sensors show a detection limit of ca. 10(8) (CFU/mL).min in a 1.5 µL microfluidic chamber with an additional setup time of 50 min. The potentials, advantages and limitations of the method are also discussed.
Subject(s)
Bacterial Load/instrumentation , Dielectric Spectroscopy/instrumentation , Lab-On-A-Chip Devices/instrumentation , Microelectrodes , Staphylococcus epidermidis/isolation & purification , Urinalysis/instrumentation , Aluminum Oxide/chemistry , Bacterial Load/methods , Biosensing Techniques/instrumentation , Electroplating , Equipment Design , Equipment Failure Analysis , Staining and Labeling/methods , Surface PropertiesABSTRACT
The only practical means of making a clinical measurement of oxygen flux into a cornea under a contact lens is by pressing a Clark-type oxygen sensor to the anterior surface of the lens. The earlier limitation to lenses of low water content has been removed and a general method suitable for soft lenses of all transmissibility is presented here. The procedure allows an estimate of oxygen tension under the lens and oxygen flux into the cornea. The method requires a minimum amount of calculation and does not require a prior calibration on the contact lens wearer, but instead gives a direct, absolute measurement of oxygen tension and flux.
Subject(s)
Contact Lenses, Hydrophilic/standards , Cornea/physiology , Oxygen Consumption , Humans , Models, Biological , Oxygen/physiology , PermeabilityABSTRACT
No oxygen was detected on the corneal surface of human subjects breathing air or almost pure oxygen. These results suggest that the epithelium obtains all its oxygen fro the air or the palpebral conjunctiva and that the endothelium is supplied with oxygen solely by the aqueous humor.
