The high demand for monoclonal antibody (mAb) therapeutics in recent years has resulted in significant efforts to improve their costly manufacturing process. The high cost of manufacturing mAbs derives mainly from the purification process, which contributes to 50%-80% of the total manufacturing cost. One of the main challenges facing industry at the purification stage is the clearance of host cell proteins (HCPs) that are produced and often co-purified with the desired mAb product. One of the issues HCPs can cause is the degradation of the final mAb protein product. In this review, techniques are considered that can be used at different stages (upstream and downstream) of mAb manufacture to improve HCP clearance. In addition to established techniques, many new approaches for HCP removal are discussed that have the potential to replace current methods for improving HCP reduction and thereby the quality and stability of the final mAb product.

RNA aptamers bind specifically and selectively to various macromolecules, cell surfaces, and viruses and find broad applications as biosensors, diagnostics, and in therapeutic treatments and drug delivery. Currently, RNA aptamer production is via in vitro methods. Herein, a new E. coli-based approach has been demonstrated for the rapid production of multimeric RNA aptamer transcripts that are protected from degradation by burying the 5' and 3' ends of the transcript in a designed double-stranded spacer. Multimeric and fluorescent RNA aptamers were produced stably in vivo and readily isolated from RNase III-deficient cells, and their full functionalities were shown by binding assays and fluorescence measurements. This approach shows promise as a rapid and scalable bioprocess for the production of RNA aptamers at low cost.

Leptospirosis is a potentially life-threatening zoonosis caused by pathogenic Leptospira and for rapid diagnostics, direct detection is desirable. LipL32 protein is the most suitable biomarker for direct detection. DNA aptamers are sought to be generated against LipL32 by Systemic Evolution of Ligands via Exponential Enrichment (SELEX). LepDapt-5a is the most potent aptamer candidate among all the candidates, as determined by direct Enzyme-linked Aptasorbent Assay (ELASA). LepDapt-5a was predicted to form a G-quadruplex structure as predicted by QGRS Mapper and validated experimentally by direct ELASA. The diagnostic potential of the aptamer was further tested on a direct and sandwich ELASA platform. A LOD of 106 mL-1 and 105 mL-1 were estimated by direct and sandwich ELASA platforms, respectively, which are within the range associated with leptospiremia levels. The dot blot assay developed was able to attain a LOD of 104 CFU mL-1 against pathogenic Leptospira, which is also within the leptospiremia level. This is the first-ever DNA aptamer and hybrid-heterodimeric aptamer constructed against LipL32. The diagnostic potentiality of the LepDapt-5a DNA aptamer was proven on three major diagnostic platforms, which are direct ELASA, sandwich ELASA, and aptamer-based dot assay.

BACKGROUND: The identification of protein-protein interactions is a great challenge. In this study, we fabricated a gold surface-modified biochip with activated sophorolipids (SLs) in combination with 16-amino-1-hexadecanethiol hydrochloride to detect serum proteins. MAIN METHODS AND MAJOR RESULTS: The on-chip immunoassay reported here included a forward assay, in which a ligand is immobilized on the biochip surface and allowed to interact with its free specific receptor in liquid phase, and a reverse assay, in which a receptor is loaded on the biochip surface and combined with its free specific ligand in solution. The specificity of the molecular interactions on the biochip was evaluated using immunological blocking assays and chemiluminescent immunoassays (CLIA). Hemophagocytic lymphohistiocytosis (HLH) serum was used to test the potential utilization of the biochip. Reverse receptor CD25-based interleukin (IL)-2 and forward ligand IL-2-based CD25 assays revealed that the limit of detection of the target proteins was as low as 156 and 78 pg/ml, respectively. Using receptor- or ligand-based platforms, we found that the positive rates of free IL-2 and soluble CD25 (sCD25) monomers in the sera of HLH patients were 14.3% and 71.4%, respectively. In addition, the biochip showed good compatibility with CLIA for the measurement of sCD25 (r = 0.77, p < 0.01). CONCLUSIONS AND IMPLICATIONS: Biochip platforms, such as on-chip immunoprecipitation (IP), can be used to evaluate the interactions between proteins, ligands, and receptors, or enzymes and substrates in serum.