Nano-Silica Carriers Coated by Chloramphenicol: Synthesis, Characterization, and Grinding Trial as a Way to Improve the Release Profile

Silica nanoparticles were applied as the carrier of chloramphenicol (2,2-dichloro-N-[(1R,2R)-1,3-dihydroxy-1-(4-nitrophenyl)propan-2-yl]acetamide), and were loaded in a 1% carbopol-based gel (poly(acrylic acid)), which allowed obtainment of an upgraded drug form. The samples of silica materials were obtained by means of modified Stöber synthesis, and their morphological properties were analyzed using Fourier transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) method, elemental analysis (EA), thermogravimetric analysis (TGA), analysis of the specific surface properties, X-ray diffraction study (XRD), scanning electron microscope (SEM), and dynamic light scattering (DLS) methods, which permitted the selection of the drug carrier. The two obtained silica carriers were coated with chloramphenicol and loaded into 1% carbopol gel. The release studies were then performed. The release results were evaluated using mathematical models as well as model-independent analysis. It was found that the modification of the synthesis of the silica by the sol-gel method to form a product coated with chloramphenicol and further grinding of the silica material influenced the release of the active substance, thus allowing the modification of its pharmaceutical availability. The change in the parameters of silica synthesis influenced the structure and morphological properties of the obtained silica carrier. The grinding process determined the way of adsorption of the active substance on its surface. The studies showed that the proper choice of silica carrier has a considerable effect on the release profile of the prepared hydrogel formulations.

Immobilization of the Highly Active UDP-Glucose Pyrophosphorylase From Thermocrispum agreste Provides a Highly Efficient Biocatalyst for the Production of UDP-Glucose

Biocatalysis that produces economically interesting compounds can be carried out by using free enzymes or microbial cells. However, often the cell metabolism does not allow the overproduction or secretion of activated sugars and thus downstream processing of these sugars is complicated. Here enzyme immobilization comes into focus in order to stabilize the enzyme as well as to make the overall process economically feasible. Besides a robust immobilization method, a highly active and stable enzyme is needed to efficiently produce the product of choice. Herein, we report on the identification, gene expression, biochemical characterization as well as immobilization of the uridine-5′-diphosphate-glucose (UDP-glucose) pyrophosphorylase originating from the thermostable soil actinobacterium Thermocrispum agreste DSM 44070 (TaGalU). The enzyme immobilization was performed on organically modified mesostructured cellular foams (MCF) via epoxy and amino group to provide a stable and active biocatalyst. The soluble and highly active TaGalU revealed a V_max of 1698 U mg^–1 (uridine-5′-triphosphate, UTP) and a K_m of 0.15 mM (UTP). The optimum reaction temperature was determined to be 50°C. TaGalU was stable at this temperature for up to 30 min with a maximum loss of activity of 65%. Interestingly, immobilized TaGalU was stable at 50°C for at least 120 min without a significant loss of activity, which makes this enzyme an interesting biocatalyst for the production of UDP-glucose.

Statement on the safety and efficacy of phosphoric acid 60% on silica carrier (UD60) for all animal species

The additive UD60 (phosphoric acid 60% on silica carrier) is intended to be used as a technological additive (functional group: preservative) for all animal species. The Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) assessed the data provided by the applicant in the technical dossier. During the course of the assessment, the need for additional information in order to be able to deliver an opinion on the safety and efficacy of this additive was identified and notified to the applicant. The information requested covered the characterisation, the safety for the target species and the efficacy of the additive. The applicant has failed to provide the additional information. Therefore, considering the data provided in the original dossier and the absence of response from the applicant to the requests from EFSA, the FEEDAP Panel is not in a position to deliver an opinion on the safety and efficacy of the additive UD60 (phosphoric acid 60% on silica carrier) as a technological additive for all animal species.