A general approach to site-specific antibody drug conjugates.

Using an expanded genetic code, antibodies with site-specifically incorporated nonnative amino acids were produced in stable cell lines derived from a CHO cell line with titers over 1 g/L. Using anti-5T4 and anti-Her2 antibodies as model systems, site-specific antibody drug conjugates (NDCs) were produced, via oxime bond formation between ketones on the side chain of the incorporated nonnative amino acid and hydroxylamine functionalized monomethyl auristatin D with either protease-cleavable or noncleavable linkers. When noncleavable linkers were used, these conjugates were highly stable and displayed improved in vitro efficacy as well as in vivo efficacy and pharmacokinetic stability in rodent models relative to conventional antibody drug conjugates conjugated through either engineered surface-exposed or reduced interchain disulfide bond cysteine residues. The advantages of the oxime-bonded, site-specific NDCs were even more apparent when low-antigen-expressing (2+) target cell lines were used in the comparative studies. NDCs generated with protease-cleavable linkers demonstrated that the site of conjugation had a significant impact on the stability of these rationally designed prodrug linkers. In a single-dose rat toxicology study, a site-specific anti-Her2 NDC was well tolerated at dose levels up to 90 mg/kg. These experiments support the notion that chemically defined antibody conjugates can be synthesized in commercially relevant yields and can lead to antibody drug conjugates with improved properties relative to the heterogeneous conjugates formed by nonspecific chemical modification.

Biosensor based on nanocomposite material for pathogenic virus detection.

This paper introduces a DNA biosensor based on a DNA/chitosan/multi-walled carbon nanotube nanocomposite for pathogenic virus detection. An easy, cost-effective approach to the immobilization of probe DNA sequences on the sensor surface was performed. Cyclic voltammograms were used to characterize the probe DNA sequence immobilization. Complementary sequence hybridization was examined by electrochemical impedance spectroscopy. Results revealed that the developed DNA sensor can detect a target DNA concentration as low as 0.01×10(-12) M. The sensitivity of the prepared sensor was 52.57 kΩ/fM. The reusability and storage stability of the DNA sensor were also investigated. Results showed that the electron-transfer resistance decreased to approximately 35% after 8 weeks and to approximately 80% after 12 weeks of storage.