The use of intracellular dyes to create a multiplexed flow cytometry-based red blood cell phenotyping assay.

BACKGROUND AND OBJECTIVES: Flow cytometry can be used to phenotype red blood cell antigens, allowing for high-throughput testing while using low reagent volumes. This article utilizes intracellular dyes to pre-label red blood cells to further multiplex flow cytometry-based red blood cell antigen phenotyping. MATERIALS AND METHODS: Red blood cells were pre-labelled using the intracellular dyes V450 and Oregon Green. These dyes are detected fluorescently via flow cytometry. Four combinations of intracellular staining were used to allow four patient or donor red blood cells to be analysed in a single test well. Antigen phenotyping was then performed via flow cytometry using a previously described method. RESULTS: The intracellular dyes showed uniform staining when measured in mean fluorescence intensity and allowed the red blood cells to be clearly distinguished from one another. The presence or absence of red blood cell antigens was determined with 100% accuracy. CONCLUSION: The use of intracellular dyes allowed a fourfold increase in the throughput of our previously described flow cytometry-based red blood cell antigen phenotyping method. The described method allows up to 48 patients to be simultaneously phenotyped using a single 96-well microplate. Furthermore, additional fluorescent dyes could potentially increase the throughput exponentially.

Development of multiplexed flow cytometry-based red blood cell antibody screen and identification assays.

BACKGROUND AND OBJECTIVES: The purpose of this study was to develop a high-throughput method of performing red blood cell antibody screens and identification by utilizing flow cytometry and intracellular dyes to allow a multiplexed assay where three-cell screens can be performed in a single test well and 11-cell panels in three test wells. MATERIALS AND METHODS: Reagent red blood cells were labelled using Violet Proliferation Dye 450 (V450) and Oregon Green fluorescent dyes, which bind intracellular proteins to allow up to four cells to be interrogated in a single test well. Sixteen 3-cell screen panels and ten 11-cell identification panels were tested using sera with known antibody specificity. Antibody binding was detected using secondary anti-immunoglobulin G and anti-immunoglobulin M fluorescently labelled antibodies. RESULTS: Intracellular dyes allowed clear separation of the different screen and identification panel test cells. Three distinct populations of V450+, Oregon Green+ and negative for both stains were demonstrated in the screening panel and an additional double positive for V450 and Oregon Green was utilized to include a fourth cell in the identification panel testing to increase throughput. A total of 158 screen or identification panel RBC/serum combinations were tested against different known antibodies, and expected results were obtained with 100% concordance. CONCLUSION: This study demonstrates the successful development of a high-throughput multiplexed flow cytometry-based red cell antibody screen and identification panel assays. This method could be implemented in clinical laboratories to complement existing antibody detection methods. The multiplexing enabled via intracellular staining could be utilized to further augment other flow cytometry-based transfusion assays.

Use of surgical sperm retrieval in azoospermic men: a meta-analysis.

OBJECTIVE: To compare the outcome of intracytoplasmic sperm injection (ICSI) cycles [1] using epididymal and testicular sperm in patients with obstructive azoospermia (OA); [2] using surgically retrieved sperm in patients with OA and nonobstructive azoospermia (NOA); and [3] using fresh and frozen-thawed sperm. DESIGN: Meta-analysis of published data. SETTING: Assisted conception unit. PATIENT(S): Ten reports (734 cycles: 677 transfers) were identified as suitable to assess source of sperm; 9 reports (1,103 cycles: 998 transfers) to assess etiology; and 17 reports (1,476 cycles: 1,377 transfers) to assess the effect of cryopreservation. INTERVENTION(S): Surgical sperm retrieval/ICSI. MAIN OUTCOME MEASURE(S): Fertilization rate (FR), implantation rate (IR), clinical pregnancy rate (CPR), and ongoing pregnancy rate (OPR) per embryo transfer. RESULT(S): Meta-analysis demonstrated no significant difference in any outcome measure between the use of epididymal or testicular sperm in men with OA. Meta-analysis showed a significantly improved FR (relative risk [RR] 1.18; 95% confidence interval [CI]: 1.13-1.23) and CPR (RR 1.36; 95% CI: 1.10-1.69) in men with OA as compared to NOA with a nonsignificant increase in OPR. There was no difference in either IR or miscarriage rate between the two groups. Comparing fresh with frozen-thawed epididymal sperm there was no difference in FR or IR, a significantly higher CPR (RR 1.20; 95% CI: 1.0-1.42), and no difference in OPR. No difference in fertilization or pregnancy outcome was noted when the testicular cycles were analyzed separately, but IR was significantly impaired using frozen-thawed sperm (RR 1.75; 95% CI: 1.10-2.80). CONCLUSION(S): Meta-analysis of published data confirms that etiology of azoospermia and cryopreservation of surgically retrieved sperm impacts on ICSI outcome, and allows us to make several recommendations for clinical practice. Origin of sperm, in men with similar etiology, does not affect outcome.

Functional molecular wires.

The properties of self-assembled molecules may be tuned by sequentially coupling components on a gold surface, the molecular electronics toolbox of chemically reactive building blocks yielding molecular wires with diode-like current-voltage (I-V) characteristics. The bias for rectification in each case is dependent upon the sequence of electron-donating and electron-accepting moieties and similar behaviour has been achieved for four different contacting techniques.