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Abstract We report in this article the microwave synthesis of relatively monodisperse, highly crystalline CdSe quantum dots (QDs) overcoated with Cd0.5Zn0.5S/ZnS multishells. The as-prepared QDs exhibited narrow photoluminescence bandwidth as the consequence of homogeneous size distribution and uniform crystallinity, which was confirmed by transmission electron microscopy. A high photoluminescence quantum yield up to 80% was measured for the core/multishell nanocrystals. Finally, the resulting CdSe/Cd0.5Zn0.5S/ZnS core/multishell QDs have been successfully applied to the labeling and imaging of breast cancer cells (SK-BR3).

An electrochemical enzyme-linked immobilized DNA-hybridization assay for the detection of Plasmodium falciparum has been developed. The target molecule was a segment of the repeat sequence of the gene coding for the circumsporozoite (CSP) protein from the AF54087 gene. This analyte offers the possibility of specifically detecting P. faleiparum. The assay involves attachment of a biotinylated primary DNA probe via its 5'-amineterminus to the streptavidin-coated surface of microwells in a 96-well plate. The primary DNA probe (1 [sup.0]P, which was of two different sequences we call 1[sup.0][P.sub.a] and 1 [sup.0][P.sub.b]) was used to capture the target (T, which was of two different sequences, [T.sub.1] sequence 481-590 and [T.sub.2] sequence 472-590 of AF54087 gene for the CSP gene) by hybridization to a complementary sequence on the target. On 1 [sup.0][P.sub.a], 47 bases were complementary to [T.sub.1] and [T.sub.2] at 543-590, while on 1 [sup.0][P.sub.b]], 35 bases were complementary to [T.sub.1] and [T.sub.2] at 555-590. A secondary DNA probe that contained 36 bases with alkaline phosphatase (2[sup.0]P-AP) label on the 3' end was hybridized to a complementary base sequence on the 5' end of the target, p-Aminophenol, which is enzymatically generated by the immobilized AP fromp-aminophenyl phosphate (PAPP), is detected using electrochemistry. The peak current of cyclic voltammo-grams from a PAPP solution incubated inside the microwells modified with the complete assembly of the assay components gives a linear relationship with the concentration of the target (2-50 ng/mL, where [P.sub.1][ ([P.sub.1a] and [P.sub.1b]) and [P.sub.2]-AP concentrations are 50 ng/mL). A detection limit of 1.4 ng/mL (or 46 pM) of the DNA target was obtained. The signals of the assays were not significantly affected when performed in the presence of human hepatocytes, pig liver, or chicken serum indicating the viability of this assay in real clinical samples.

A new approach is reported for analysis of ultrasmall volumes. It takes advantage of the versatile positioning of a dispenser to shoot ~150-pL droplets of liquid onto a specific location of a substrate where analysis is performed rapidly, in a fraction of the time that it takes for the droplet to evaporate. In this report, the site where the liquid is dispensed carries out fast-scan cyclic voltammtry (FSCV), although the detection method does not need to be restricted to electrochemistry. The FSCV is preformed at a microactivity having individually addressable gold electrodes, where one serves as working electrode and another as counter/pseudoreference electrode. Five or six droplets of 10 mM [[Ru(N[H.sub.3]).sub.6]] [Cl.sub.3] in 0.1 M KCl were dispensed and allowed to dry, followed by redissolution of the redox species and electrolyte with one or five droplets of water and immediate FSCV, demonstrating the ability to easily concentrate a sample and the reproducibility of redissolution, respectively. Because this approach does not integrate detection with microfluidics on the same chip, it simplifies fabrication of devices for analysis of ultrasmall volumes. It may be useful for singlestep and multistep sample preparation, analyses, and bioassays in microarray formats if dispensing and changing of solutions are automated. However, care must be taken to avoid factors that affect the aim of the dispenser, such as drafts and clogging of the nozzle.