Design and Evaluation of a Surfactant–Mixed Metal Hydroxide-Based Drilling Fluid for Maintaining Wellbore Stability in Coal Measure Strata

Co-exploitation of coal measure gases (coalbed gas, shale gas, and tight sandstone gas) puts a higher requirement on drilling fluids. Conventional drilling fluids have disadvantages, such as causing problems of borehole collapse, formation damage, and water blockage. This paper proposes a set of high inhibitive and low-damage drilling fluids that function by electrical inhibition and neutral wetting. Zeta potential results showed that the negative electrical property of Longtan coal in Bijie, Guizhou, can be reversed by organic mixed metal hydroxide (MMH) and the cationic surfactant alkyl trimethylammonium bromide (CS-5) from −3.63 mV to 19.75 mV and 47.25 mV, respectively. Based on the contact angle and Fourier Transform Infrared Spectroscopy (FT-IR) results, it can be concluded that chemical adsorption dominates between the Longmaxi shale and surfactants, and physical adsorption between the Longtan coal and surfactants. A compound surfactant formula (0.001 wt% CS-4 + 0.001 wt% CS-1 + 0.001 wt% CS-3), which could balance the wettability of the Longmaxi shale and the Longtan coal, making them both appear weakly hydrophilic simultaneously, was optimized. After being treated by the compound surfactants, the contact angles of the Longmaxi shale and the Longtan coal were 89° and 86°, respectively. Pressure transmission tests showed that the optimized combination of compound surfactants and inorganic MMH (MMH-1) could effectively reduce permeability of the Longmaxi shale and the Longtan coal, thus retarding pore pressure transmission in coal measure strata. Then, the proposed water-based drilling fluid (WBDF) system (4 wt% sodium bentonite + 1.5 wt% sodium carboxymethyl cellulose + 2 wt% lignite resin + 5 wt% potassium chloride + 3 wt%MMH-1 + 0.001 wt% CS-4 + 0.001 wt% CS-1 + 0.001 wt% CS-3) was evaluated based on parameters including rheology, American Petroleum Institute (API) filtration, electrical property, wettability, inhibition capability, reservoir protection characteristics, and anti-pollution performance. It had an API filtration of 7 mL, reservoir damage rate of 10%, moderate and acceptable viscosity, strong inhibition capability to coal measure strata rocks, good tolerance to inorganic pollutants and drilling cuttings, and environmentally friendly properties. It could meet wellbore stability and reservoir protection requirements in the co-exploitation of coal measure gases

Effective preparation of a monoclonal antibody against human chromogranin A for immunohistochemical diagnosis

Abstract Background Human chromogranin A (CgA) is a ~ 49 kDa secreted protein mainly from neuroendocrine cells and endocrine cells. The CgA values in the diagnosis of tumor, and in the potential role in prognostic and predictive tumor as a biomarker. Results The synthesized gene of CgA coding area was cloned and expressed as fusion protein CgA-His in procaryotic system. Then the purified CgA-His protein was mixed with QuickAntibody-Mouse5W adjuvant, and injected into mice. The CgA-His protein was also used as coating antigen to determine the antiserum titer. By screening, a stable cell line named 4E5, which can generate anti-CgA monoclonal antibody (mAb), was obtained. The isotype of 4E5 mAb was IgG2b, and the chromosome number was 102 ± 4. Anti-CgA mAb was purified from ascites fluid, and the affinity constant reached 9.23 × 109 L/mol. Furthermore, the specificity of the mAb was determined with ELISA, western blot and immunohistochemistry. Results indicated that the mAb 4E5 was able to detect chromogranin A specifically and sensitively. Conclusions A sensitive and reliable method was successfully developed for rapid production of anti-CgA mAb for immunohistochemistry diagnosis in this study, and the current study also provides conclusive guidelines for preparation of mAbs and implements in immunohistochemistry diagnosis

Generation and characterization of a monoclonal antibody against human BCL6 for immunohistochemical diagnosis.

BackgroundHuman B-cell lymphoma 6 (BCL6) gene, usually coding protein of 706 amino acids, is closely associated with large B cell lymphoma. Researches showed that protein mutation or change of expression levels usually happened in the mounting non-hodgkin lymphoma (NHL). Thus BCL6 is considered to be involved in germinal center (GC)-derived lymphoma.ResultsThe BCL61-350 gene codons were optimized for prokaryotic system. After expression of BCL61-350 in E. coli, the BCL61-350 protein was purified with Ni column. Then the BCL61-350 protein, mixing with QuickAntibody-Mouse5W adjuvant, was injected into Balb/c mice. After immunization and cell fusion, a stable cell line named 1E6A4, which can secrete anti-BCL6 antibody, was obtained. The isotype of 1E6A4 mAb was determined as IgG2a, and the affinity constant reached 5.12×1010 L/mol. Furthermore, the specificity of the mAb was determined with ELISA, western blot and immunohistochemistry. Results indicated that the 1E6A4 mAb was able to detect BCL6 specifically and sensitively.ConclusionsBCL61-350 antigen has been successfully generated with an effective and feasible method, and a highly specific antibody named 1E6A4 against BCL6 has been screened and characterized in this study, which was valuable in clinical diagnosis