Abstract
In the first part of thesis, we have presented a sensitive electrochemical immunoassay system for the detection of a protein tumor marker, carcinoembryonic antigen (CEA), that is based on a carbon nanoparticle (CNP)/poly(ethylene imine) (PEI)-modified screen-printed graphite electrode (CNP–PEI/SPGE) covered with anti-CEA antibodies. The signal amplification strategy–using CdS nanocrystals as biotracers and CNPs to enhance electron transfer–improves the sensitivity and detection limit for CEA, suggesting that this system holds promise for development into a point-of-care or disposable home-care self-diagnostic tool. This biosensor is based on a sandwich complex immunoassay, which we assembled from sequential layers of the anti-CEA antibody (□CEA) on CNP–PEI/SPGE, the CEA sample, and the CdS nanocrystal quantum dots (QDs) sensitized with □CEA (□CEA–CdS QD). We used square wave anodic stripping voltammetry (SWASV) to amplify the signal current response obtained from the dissolved □CEA–CdS QDs. The calibration curve for CEA concentration was linear in the range of 0.032–10 ng/mL; the detection limit (estimated as the mean of the blank sample plus three times the standard deviation obtained on the blank sample) was 32 pg/mL (equivalent to 160 fg in a 5 □L sample). This method is suitably precise and sensitive to function as a means of determining urinary CEA, which is a better marker than serum CEA for the early detection of urothelial carcinoma. In the second part of thesis, a simple-used and programmable injection device was developed, using syringe filter and glass device, to manufacture liposomes with high encapsulation efficiency based on double emulsion template. First of all, aqueous solutions and lipids in chloroform were injected into the glass device by infusion pumps respectively to form water-in-oil-in-water double emulsions. It was followed by the removal of chloroform by rotary evaporator for converting double emulsions to liposomes. At the end of the process, non-encapsulated fluorescent dye molecules were separated from liposomes by dialysis. The encapsulation efficiencies of liposomes are around 26%, and the expected size of liposomes could be achieved by syringe filter membranes with designated pore size. This device is workable with neither sonicator nor delicate microfluidic system, and is suitable for manufacture of liposomes as carriers of signal molecules or drugs with high encapsulation efficiency.