Surface Modification of Polystyrene with Boronic Acid for Immunoaffinity-Based Cell Enrichment.

Obtaining an enriched and phenotypically pure cell population from heterogeneous cell mixtures is important for diagnostics and biosensing. Existing techniques such as fluorescent-activated cell sorting (FACS) and magnetic-activated cell sorting (MACS) require preincubation with antibodies (Ab) and specialized equipment. Cell immunopanning removes the need for preincubation and can be done with no specialized equipment. The majority of the available antibody-mediated analyte capture techniques require a modification to the Abs for binding. In this work, no antibody modification is used because we take advantage of the carbohydrate chain in the Fc region of Ab. We use boronic acid as a cross-linker to bind the Ab to a modified surface. The process allows for functional orientation and cleavable binding of the Ab. In this study, we created an immunoaffinity matrix on polystyrene (PS), an inexpensive and ubiquitous plastic. We observed a 37% increase in Ab binding compared with that of a passive adsorption approach. The method also displayed a more consistent antibody binding with 17 times less variation in Ab loading among replicates than did the passive adsorption approach. Surface topography analysis revealed that a dextran coating reduced nonspecific antibody binding. Elemental analysis (XPS) was used to characterize the surface at different stages and showed that APBA molecules can bind upside-down on the surface. While upside-down antibodies likely remain functional, their elution behavior might differ from those bound in the desired way. Cell capture experiments show that the new surface has 43% better selectivity and 2.4-fold higher capture efficiency compared to a control surface of passively adsorbed Abs. This specific surface chemistry modification will allow the targeted capture of cells or analytes with the option of chemical detachment for further research and characterization.

Droplets for Sampling and Transport of Chemical Signals in Biosensing: A Review.

The chemical, temporal, and spatial resolution of chemical signals that are sampled and transported with continuous flow is limited because of Taylor dispersion. Droplets have been used to solve this problem by digitizing chemical signals into discrete segments that can be transported for a long distance or a long time without loss of chemical, temporal or spatial precision. In this review, we describe Taylor dispersion, sampling theory, and Laplace pressure, and give examples of sampling probes that have used droplets to sample or/and transport fluid from a continuous medium, such as cell culture or nerve tissue, for external analysis. The examples are categorized, as follows: (1) Aqueous-phase sampling with downstream droplet formation; (2) preformed droplets for sampling; and (3) droplets formed near the analyte source. Finally, strategies for downstream sample recovery for conventional analysis are described.

Strategically Designing a Pumpless Microfluidic Device on an "Inert" Polypropylene Substrate with Potential Application in Biosensing and Diagnostics.

This study is an attempt to make a step forward to implement the very immature concept of pumpless transportation of liquid into a real miniaturized device or lab-on-chip (LOC) on a plastic substrate. "Inert" plastic materials such as polypropylene (PP) are used in a variety of biomedical applications but their surface engineering is very challenging. Here, it was demonstrated that with a facile innovative wettability patterning route using fluorosilanized UV-independent TiO2 nanoparticle coating it is possible to create wedge-shaped open microfluidic tracks on inert solid surfaces for low-cost biomedical devices (lab-on-plastic). For the future miniaturization and integration of the tracks into a device, a variety of characterization techniques were used to not only systematically study the surface patterning chemistry and topography but also to have a clear knowledge of its biological interactions and performance. The effect of such surface architecture on the biological performance was studied in terms of static/dynamic protein (bovine serum albumin) adsorption, bacterial (Staphylococcus aureus and Staphylococcus epidermidis) adhesion, cell viability (using HeLa and MCF-7 cancer cell lines as well as noncancerous human fibroblast cells), and cell patterning (Murine embryonic fibroblasts). Strategies are discussed for incorporating such a confined track into a diagnostic device in which its sensing portion is based on protein, microorganism, or cells. Finally, for the proof-of-principle of biosensing application, the well-known high-affinity molecular couple of BSA-antiBSA as a biological model was employed.

Evaluation of vasomotor reactivity in systemic lupus erythematosus patients and its comparison with the control group.

BACKGROUND: Neuropsychiatric abnormalities are among the most common manifestations of systemic lupus erythematosus (SLE). They have been proposed to be associated with impaired cerebral blood flow (CBF). Cerebral vasomotor reactivity (VMR) is a hemodynamic parameter effective in the autoregulation of CBF. The aim of the present study is to determine and compare the VMR of women with stable SLE and normal women. MATERIALS AND METHODS: According to the study criteria 60 women in each group entered the study. VMR was evaluated with Transcranial Doppler (TCD) at rest and after one minute of breath holding. RESULTS: There was no significant difference in the mean of age between two groups (31.76 ± 7.50 years in the SLE group versus 32.43 ± 4.55 years in the control group, P value: 0.64). The mean duration of SLE in the case group was 5.40 ± 3.60 years. The means of the Breath-Holding Index (BHI) in the SLE and control groups were 0.842 ± 0.72% and 0.815 ± 0.26%, respectively, which was not significantly different (P value: 0.82). CONCLUSION: This study indicates that the VMR of women with stable SLE is not significantly different from the age- and sex-matched normal population. However, further investigations on patients with longer SLE duration and more neuropsychological abnormality rates are suggested.

Quantitative Analysis of GABAA Gamma Receptor Subunits in the Developing Embryonic Chick Forebrain.

OBJECTIVES: In this study we investigated the expression of GABAA receptor subunits during brain development. These receptors may change in the embryonic chick forebrain. MATERIALS AND METHODES: The expression levels of four types of GABAA receptor gamma subunits (γ1, γ2, γ3 and γ4) were quantified in the embryonic chick forebrain at 32 hr, 3, 7, 14, and 20 days of incubation and day one after hatching. The expression level of mRNA in the forebrain of embryonic chicken was measured using real-time RT-PCR. RESULTS: The expression level of each subunit increased gradually with development and reached a plateau on 20th day of embryonic development. A reduction was observed on day one after hatching in all gamma subunits. CONCLUSION: This may explain the different physiological and pharmacological function of GABA receptor gamma subunits before and after hatching.