Artificial antibody-antigen-directed immobilization of lipase for consecutive catalytic synthesis of ester: Benzyl acetate case study.

A strategy based on artificial antibody-antigen recognition was proposed for the specific directed immobilization of lipase. The artificial antibody was synthesized using catechol as a template, α-methacrylic acid as a functional monomer, and Fe3O4 as the matrix material. Lipase was modified with 3,4-dihydroxybenzaldehyde as an artificial antigen. The artificial antibody can specifically recognize catechol fragment in the enzyme structure to achieve the immobilization of lipase. The immobilization amount, yield, specific activity, and immobilized enzyme activity were 13.2 ± 0.2 mg/g, 78.9 ± 0.4 %, 7.9 ± 0.2 U/mgprotein, and 104.6 ± 1.7 U/gcarrier, respectively. Moreover, the immobilized lipase exhibited strong reusability and regeneration ability. Additionally, the immobilized lipase successfully catalyzed the synthesis of benzyl acetate and demonstrated robust continuous catalytic activity. These results fully demonstrate the feasibility of the proposed artificial antibody-antigen-directed immobilization of lipase.

Assessment of Tribo-charging and Continuous Feeding Performance of Direct Compression Grades of Isomalt and Mannitol Powders.

Tribo-charging is often a root cause of mass flow deviations and powder adhesion during continuous feeding. Thus, it may critically impact product quality. In this study, we characterized the volumetric (split- and pre-blend) feeding behavior and process-induced charge of two direct compression grades of polyols, galenIQ™ 721 (G721) for isomalt and PEARLITOL® 200SD (P200SD) for mannitol, under different processing conditions. The feeding mass flow range and variability, hopper end fill level, and powder adhesion were profiled. The feeding-induced tribo-charging was measured using a Faraday cup. Both materials were comprehensively characterized for relevant powder properties, and their tribo-charging was investigated for its dependence on particle size and relative humidity. During split-feeding experiments, G721 showed a comparable feeding performance to P200SD with lower tribo-charging and adhesion to the screw outlet of the feeder. Depending on the processing condition, the charge density of G721 ranged from -0.01 up to -0.39 nC/g, and for P200SD from -3.19 up to -5.99 nC/g. Rather than differences in the particle size distribution of the two materials, their distinct surface and structural characteristics were found as the main factors affecting their tribo-charging. The good feeding performance of both polyol grades was also maintained during pre-blend feeding, where reduced tribo-charging and adhesion propensity was observed for P200SD (decreasing from -5.27 to -0.17 nC/g under the same feeding settings). Here, it is proposed that the mitigation of tribo-charging occurs due to a particle size-driven mechanism.

Temperature cycling-induced formation of crystalline coatings.

The surface of particles is the hotspot of interaction with their environment and is therefore a major target for particle engineering. Particles with tailored coatings are greatly desired for a range of different applications. Amorphous coatings applied via film coating or microencapsulation have frequently been described in the pharmaceutical context and usually result in homogeneous surfaces. In the present study we have been exploring the feasibility of coating core particles with crystalline substances, a matter that has rarely been investigated. The expansion of the range of possible coating materials to include small organic molecules enables completely new product properties to be achieved. We present an approach based on temperature cycles performed in a tubular crystallizer to result in engineered crystalline coatings on excipient core particles. By manipulating the process settings and by the choice of coating substance we are able to tailor surface roughness, topography as well as surface chemistry. Benefits of our approach are demonstrated by using resulting particles as carriers in dry-powder-inhaler formulations. Depending on the resulting surface chemistry and surface roughness, coated carrier particles show varying fitness for delivering the model API salbutamol sulphate to the lung.