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Gold nanoparticles (AuNPs) exhibit a unique phenomenon, known as surface plasmon resonance, which is responsible for their large absorption and scattering cross-sections, which are four to five orders of magnitude larger than those of conventional dyes. In addition, their optical properties can be controlled by varying their sizes, shapes and compositions. AuNPs can be easily synthesized and functionalized with different biomolecules including oligonucleotides. Numerous methods have been utilized for detecting AuNPs such as colorimetric, scanometric, fluorescence, surface-enhanced Raman scattering and electrochemical techniques. These unique aspects have permitted the development of novel AuNP-based assays for molecular diagnostics which promise increased sensitivity and specificity, multiplexing capability, and short turnaround times. AuNP-based colorimetric assays in particular show great potential in point-of-care testing assays. This review discusses properties of AuNPs and their utilization for the development of novel molecular assays.

Background: The use of nanotechnologies for diagnostic applications shows great promise to meet the rigorous demands of the clinical laboratory for sensitivity and cost-effectiveness. New nanodiagnostic tools include quantum dots (QDs), gold nanoparticles, and cantilevers. QDs, which are the most promising nanostructures for diagnostic applications, are semiconductor nanocrystals characterized by high photostability, single-wavelength excitation, and size-tunable emission. QDs and magnetic nanoparticles can be used for barcoding of specific analytes. Gold and magnetic nanoparticles are key components of the bio-barcode assay, which has been proposed as a future alternative to the PCR. Methods: We examined articles published over the past 10 years investigating the use of QDs, gold nanoparticles, cantilevers, and other nanotechnologies in promising diagnostic applications. Results: Several nanodiagnostic assays have been developed, including a QD-based assay capable of detecting biotinylated prostate-specific antigen (PSA) at 0.38 ng/L, a bio-barcode assay capable of detecting 30 amol/L PSA in a 10-L sample, and another able to detect 50 molecules of the Alzheimer marker amyloid ␤-derived diffusible ligand in 10 L of cerebrospinal fluid. Conclusions: Nanodiagnostics promise increased sensitivity, multiplexing capabilities, and reduced cost for many diagnostic applications as well as intracellular imaging. Further work is needed to fully optimize these diagnostic nanotechnologies for clinical laboratory set-

Hepatitis B virus (HBV) is a major cause of liver cirrhosis and hepatocellular carcinoma (HCC). Eight different HBV genotypes have been identified with distinct geographical distributions. Different genotyping methods exist including sequencing, INNO-LiPA, restriction fragment polymorphism (RFLP), multiplex PCR, serotyping, oligonucleotide microarray chips, reverse dot blot, restriction fragment mass polymorphism (RFMP), invader assay, and real-time PCR. Several investigators have studied the influence of HBV genotypes on clinical outcomes in chronic HBV patients. This review describes the current genotyping techniques, as well as their advantages and limitations. It also presents the clinical evidence that correlates HBV genotypes to clinical outcomes including disease severity, HCC development, response to therapy, disease chronicity, transplantation outcomes, and occult infection.

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Background: A biomarker that reliably detects myocardial ischemia in the absence of necrosis would be useful for initial identification of unstable angina patients and for differentiating patients with chest pain of an etiology other than coronary ischemia, and could provide clinical utility complementary to that of cardiac troponins, the established markers of necrosis.