OBJECTIVE: Camptothecin (CPT) is one of the most promising anticancer drugs but it produces various side effects because of its non-selectivity towards cancer cells. To overcome these adverse effects, we synthesized biotin conjugate of camptothecin, which was linked via a self-immolative disulfide linker (CPT-SS-Biotin).
METHODS: Biotin conjugated camptothecin linked through a disulfide bond was synthesized following schemes, and the structural characterization was carried out. The stability and drug release studies were performed in the presence of glutathione (GSH) while in vitro studies were performed on 4T1 tumor cell lines. In vivo pharmacological investigation was done using an antitumor Wistar rat model.
RESULTS: The stability and drug release studies were performed in the presence of glutathione (GSH), and CPT-SSBiotin was found to be physiologically stable moiety and can only be cleaved in the presence of GSH to release free CPT. The CPT-SS-Biotin showed higher toxicity in the biotin-overexpressing 4T1 tumor cell line with a lower IC50 value (8.44 μM) compared to camptothecin alone (IC50 > 30 μM). CPT-SS-Biotin also showed 10.6% higher cellular uptake by cells in comparison to free camptothecin. The CPT-SS-Biotin was delivered to cells by binding to the biotin receptors on the cell surface, followed by energy-dependent endocytosis and internalization to cause cellular toxicity.
CONCLUSION: In-vivo tumor suppression studies and in vitro cell line studies along with serological parameters and histopathological studies showed that conjugate produced a high therapeutic effect and remarkably reduced toxic effects in comparison to free CPT. The results suggested that biotinylation of camptothecin via disulfide linker can be a safe and efficacious method in cancer therapeutics.
Survey methodology and objectives: A traditional review approach was taken to focus on the engineering of microbial -amylases to enhance industrially favoured characteristics. The action mechanisms of - and -amylases were compared to avoid any bias in the research background. This review aimed to discuss the advances in modifying microbial -amylases via protein engineering to achieve longer half-life in high temperature, improved resistance (acidic, alkaline and oxidative) and enhanced specificities (substrate and product). Captivating results were discussed in depth, including the extended half-life at 100C, pH 3.5 and 10, 1.8 M hydrogen peroxide as well as enhanced substrate (65.3%) and product (42.4%) specificities. These shed light to the future microbial -amylase engineering in achieving paramount biochemical traits ameliorations to apt in the industries.
Conclusions: Microbial -amylases can be tailored for specific industrial applications through protein engineering (rational design and directed evolution). While the critical mutation points are dependent on respective enzymes, formation of disulfide bridge between cysteine residues after mutations is crucial for elevated thermostability. Amino acids conversion to basic residues was reported for enhanced acidic resistance while hydrophobic interaction resulted from mutated hydrophobic residues in carbohydrate-binding module or surface-binding sites is pivotal for improved substrate specificity. Substitution of oxidation-prone methionine residues with non-polar residues increases the enzyme oxidative stability. Hence, this review provides conceptual advances for the future microbial -amylases designs to exhibit industrially significant characteristics. However, more attention is needed to enhance substrate specificity and oxidative stability since they are least reported.