Direct in situ hybridization with oligonucleotide functionalized quantum dot probes

Aneuploidy: a common and early evidence-based biomarker for carcinogens and reproductive toxicants

Aneuploidy, defined as structural and numerical aberrations of chromosomes, continues to draw attention as an informative effect biomarker for carcinogens and male reproductive toxicants. It has been well documented that aneuploidy is a hallmark of cancer. Aneuploidies in oocytes and spermatozoa contribute to infertility, pregnancy loss and a number of congenital abnormalities, and sperm aneuploidy is associated with testicular cancer. It is striking that several carcinogens induce aneuploidy in somatic cells, and also adversely affect the chromosome compliment of germ cells. In this paper we review 1) the contributions of aneuploidy to cancer, infertility, and developmental abnormalities; 2) techniques for assessing aneuploidy in precancerous and malignant lesions and in sperm; and 3) the utility of aneuploidy as a biomarker for integrated chemical assessments of carcinogenicity, and reproductive and developmental toxicity.

Diagnosis of porcine circovirus type 2 infection with a combination of immunomagnetic beads, single-domain antibody, and fluorescent quantum dot probes

The use of a specific antibody conjugated with nanobeads, forming immunomagnetic nanobeads (IMNBs), has been demonstrated to be useful for the capture and detection of viruses. In this study, IMNBs functionalized with a single-domain antibody against the capsid protein (Cap) of porcine circovirus type 2 (PCV2), hereafter denoted as psdAb, were evaluated and used to capture PCV2. Quantum dots (QDs) conjugated with psdAb were used as a fluorescence probe to visualize PCV2 captured by IMNBs. The specificity and sensitivity of this method were further evaluated using common pathogens of pig viral disease and PCV2. To assess its practicality, clinical samples were tested in this study. The results showed that 2.57 ± 0.13 mg Cap or 0.97 ± 0.064 × 10(6) copies of PCV2 particles could be captured by 1 mg of IMNBs in 30 min. This suggests that the IMNBs have the ability to efficiently capture PCV2 with good specificity, as there was no cross-reaction with other pathogens, and with strong sensitivity, with a detection limit as low as 10(3) copies/ml of PCV2 particles. Moreover, PCV2 in inguinal lymph node, lung, spleen, serum, and fecal samples was successfully detected by IMNBs. The results demonstrate that this method is promising for the rapid and effective detection of PCV2 in complex clinical samples.

Highly sensitive single domain antibody-quantum dot conjugates for detection of HER2 biomarker in lung and breast cancer cells

Despite the widespread availability of immunohistochemical and other methodologies for screening and early detection of lung and breast cancer biomarkers, diagnosis of the early stage of cancers can be difficult and prone to error. The identification and validation of early biomarkers specific to lung and breast cancers, which would permit the development of more sensitive methods for detection of early disease onset, is urgently needed. In this paper, ultra-small and bright nanoprobes based on quantum dots (QDs) conjugated to single domain anti-HER2 (human epidermal growth factor receptor 2) antibodies (sdAbs) were applied for immunolabeling of breast and lung cancer cell lines, and their performance was compared to that of anti-HER2 monoclonal antibodies conjugated to conventional organic dyes Alexa Fluor 488 and Alexa Fluor 568. The sdAbs-QD conjugates achieved superior staining in a panel of lung cancer cell lines with differential HER2 expression. This shows their outstanding potential for the development of more sensitive assays for early detection of cancer biomarkers.

Combining M-FISH and Quantum Dot technology for fast chromosomal assignment of transgenic insertions

Background

Physical mapping of transgenic insertions by Fluorescence in situ Hybridization (FISH) is a reliable and cost-effective technique. Chromosomal assignment is commonly achieved either by concurrent G-banding or by a multi-color FISH approach consisting of iteratively co-hybridizing the transgenic sequence of interest with one or more chromosome-specific probes at a time, until the location of the transgenic insertion is identified.

Results

Here we report a technical development for fast chromosomal assignment of transgenic insertions at the single cell level in mouse and rat models. This comprises a simplified 'single denaturation mixed hybridization' procedure that combines multi-color karyotyping by Multiplex FISH (M-FISH), for simultaneous and unambiguous identification of all chromosomes at once, and the use of a Quantum Dot (QD) conjugate for the transgene detection.

Conclusions

Although the exploitation of the unique optical properties of QD nanocrystals, such as photo-stability and brightness, to improve FISH performance generally has been previously investigated, to our knowledge this is the first report of a purpose-designed molecular cytogenetic protocol in which the combined use of QDs and standard organic fluorophores is specifically tailored to assist gene transfer technology.

dsDNA-coated quantum dots

Because of their unique spectral properties, quantum dots (QDs) have recently proved useful as fluorescent labels for biosensing probes. We developed a versatile QD label by modifying dsDNA with biotin and thiol groups at opposite ends and attaching it to quantum dots via a metal-thiol bond. These dsDNA-coated QDs fluorescently label their targets through biotin-streptavidin binding and show excellent histological results when used to detect biotin-labeled chromosome probes. The dsDNA coating also circumvented the common problems of aggregation and steric hindrance that occur with other QD probes.