Co-Encapsulation of l-Asparaginase and Etoposide in Dextran Nanoparticles for Synergistic Effect in Chronic Myeloid Leukemia Cells

Co-encapsulation of multiple therapeutic drugs in a single nanocarrier has the potential to enable synergistic interactions, increase drug efficacy, and reduce side effects. The enzyme l-asparaginase and the small molecule drug etoposide have a known synergistic effect against selected cancer types. However, both drugs differ significantly in size, molecular weight, and solubility, which often results in challenges when a simultaneous delivery is required. In this study, we present the co-encapsulation of a large hydrophilic enzyme l-asparaginase and the small hydrophobic drug etoposide into a biodegradable, biocompatible, and acid-responsive dextran-based nanoparticle system. These dual drug-loaded nanoparticles show an excellent cellular uptake in chronic myeloid leukemia (CML) K562 cells and a stepwise release of the cytotoxic payloads in a pH-dependent manner. In activity tests, the dual drug-loaded formulation has shown a significant effect on cell viability (down to 31%) compared to those incubated only with l-asparaginase (92%) or etoposide (82%) at a particle concentration of 125 μg∙mL^-1. These results show that the simultaneous co-delivery of these two drugs in K562 cells leads to synergistic cytotoxicity, indicating a great potential for the treatment of CML.

Detailed algal extracellular carbohydrate-protein characterisation lends insight into algal solid-liquid separation process outcomes

The effectiveness of algal solid-liquid separation processes has been impacted by the strong influence of algal extracellular organic matter (EOM), where the composition of proteins and carbohydrates and their associated interactions have been implicated. However, despite this, no studies have analysed the detailed protein and carbohydrate composition in EOM in relation to their impacts on separation. Hence, the aim of this study was to explore the relationship between the variety of carbohydrates and proteins present in the EOM of select algal and cyanobacterial samples and the associated separation performance to better understand the influence of specific biopolymers. The protein and carbohydrate composition of the EOM of three species - Microcystis aeruginosa CS-555/1, Chlorella vulgaris CS-42/7 and Microcystis aeruginosa CS-564/01, previously observed to result in variable treatment performance were investigated. The carbohydrates were analysed via high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection (PAD) while the proteins were analysed using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) combined with liquid chromatography-mass spectrometry (LC-MS). Ten unique monosaccharides were identified; of these, the greatest proportion of charged uronic acid carbohydrates were present in the EOM of M. aeruginosa CS-564/01. The protein profiling revealed that M. aeruginosa CS-564/01 had a greater proportion and concentration of proteins >75 kDa when compared to M. aeruginosa CS-555/1 or C. vulgaris CS-42/7. It was determined that three serine- and two threonine-based proteins, detected in greater concentrations in M. aeruginosa CS-564/01 than CS-555/1, could covalently interact with carbohydrates (OHenderson et al., 2010a, 2010b-linked glycosylation). These proteins have the ability to form numerous localised networks with carbohydrates and cells in the presence of coagulant molecules, thereby providing a good hypothesis to explain the excellent treatment performance observed for M. aeruginosa CS-564/01 previously. It is proposed that the uronic acids in M. aeruginosa CS-564/01 could interact with proteins via glycosylation, explaining why the coagulant demand for this strain remained low despite the high charged carbohydrate concentration. Overall, it is proposed that process performance could be impacted by: (a) physicochemical characteristics and (b) carbohydrate-protein interactions.