The enzymatic synthesis of lactose caprate using Candida rugosa lipase immobilized into ZIF-8 and investigation of its anticancer applications against K562 leukemia and HeLa cancer cells.

In this study, a lactose fatty acid ester was enzymatically synthesised using immobilized Candida rugosa lipase (CRL). Its anticancer property against K562 leukemia and HeLa cancer cells was carefully investigated. In the first step, a de novo strategy was applied to encapsulate CRL into a microporous zeolite imidazolate framework called ZIF-8. Various characterization techniques including powder X-ray diffraction, Fourier transform infrared spectroscopy, N2 adsorption-desorption, field-emission scanning electron microscopy and thermogravimetric analysis were used to prove the successful encapsulation of CRL molecules during the formation of ZIF-8 crystals with an enzyme loading of 98% of initial CRL. The effect of various factors such as pH and temperature, affecting the enzymatic activity and reusability of the CRL@ZIF-8 composite were assessed against the free enzyme. Additionally, enzyme catalysis parameters, such as Km and Vmax, were also assessed. The obtained biocatalyst showed excellent activity in a wide pH range of 2-9 and a temperature range of 30-60 °C. According to the experimental results, the CRL@ZIF-8 composite maintained about 63% of its initial activity after 6 cycles of use. In the next step, the synthesized catalyst was applied for the synthesis of lactose caprate via enzymatic esterification of lactose with capric acid. Further experiments were performed to obtain the cytotoxicity profile of the new derivative. The growth inhibitory effect of the produced lactose caprate on K562 leukemia and HeLa cancer cells determined by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay showed its potential anticancer effects against both cell lines (IC50, 49.6 and 57.2 µg mL-1). Our results indicate that lactose caprate might be a promising candidate for further studies on K562 leukemia and HeLa cancer cells owing to its possible therapeutic usefulness.

Carbonic Anhydrase-Embedded ZIF-8 Electrospun PVA Fibers as an Excellent Biocatalyst Candidate.

There is a growing concern that the increasing concentration of CO2 in the atmosphere contributes to a potential negative impact on global climate change. To deal with this problem, developing a set of innovative, practical technologies is essential. In the present study, maximizing the CO2 utilization and precipitation as CaCO3 was evaluated. In this manner, bovine carbonic anhydrase (BCA) was embedded into the microporous zeolite imidazolate framework, ZIF-8, via physical absorption and encapsulation. Running as crystal seeds, these nanocomposites (enzyme-embedded MOFs) were in situ grown on the cross-linked electrospun polyvinyl alcohol (CPVA). The prepared composites displayed much higher stability against denaturants, high temperatures, and acidic media than free BCA, and BCA immobilized into or on ZIF-8. During 37 days of storage period study, BCA@ZIF-8/CPVA and BCA/ZIF-8/CPVA maintained more than 99 and 75% of their initial activity, respectively. The composition of BCA@ZIF-8 and BCA/ZIF-8 with CPVA improved stability for consecutive usage in recovery reactions, recycling easiness, and greater control over the catalytic process. The amounts of calcium carbonate obtained by one mg each of fresh BCA@ZIF-8/CPVA and BCA/ZIF-8/CPVA were 55.45 and 49.15 mg, respectively. The precipitated calcium carbonate by BCA@ZIF-8/CPVA reached 64.8% of the initial run, while this amount was 43.6% for BCA/ZIF-8/CPVA after eight cycles. These results indicated that the BCA@ZIF-8/CPVA and BCA/ZIF-8/CPVA fibers could be efficiently applied to CO2 sequestration.

Metal-Organic Frameworks as advanced moisture sorbents for energy-efficient high temperature cooling.

Latent cooling load accounts for 30% of the total load of air-conditioning, and its proportion is even higher in many tropical and subtropical climates. Traditional vapour-compression air-conditioning (VCAC) has a low coefficient of performance (COP) due to the refrigeration dehumidification process, which often makes necessary a great deal of subsequent re-heating. Technologies using conventional desiccants or sorbents for indoor moisture control are even less competitive than VCAC due to their high regeneration temperature, long cycling time and bulky components. Here, we report a novel high temperature cooling system that uses porous metal-organic frameworks (MOFs) as advanced sorbents for humidity control. We directly coat MOFs on the surface of evaporator and condenser. The system has no additional components compared to a traditional VCAC. The evaporator can simultaneously remove both the sensible and latent loads of the incoming air without reducing the temperature below its dew point. The regeneration of wet MOFs is completely driven by the residual heat from the condenser. The MOF-coated heat exchangers can achieve a cooling power density of 82 W·L-1. We demonstrate that the system has a high COP, up to 7.9, and can save 36.1% of the energy required, compared to the traditional VCAC system with reheating. The amphiphilic MOFs used in the research have high water uptake, are made of low-cost raw materials and have high hydrothermal stability. They thus have the potential for being scaled up for large-scale applications in air conditioning.