Key Engineering Materials Vol. 903

Abstract: Liposomes are being used as unique drug delivery systems due to their ability to encapsulate both hydrophilic and hydrophobic drugs, as well as for the fact that they improve the disadvantages of free drug administration. However, liposomes have a significant disadvantage - low encapsulation efficiency. In the research carried out, 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and cholesterol (Chol), in the ratio (n/n) of 2:1, 3:1 and 4:1 respectively, were used to prepare the liposomes. Blank liposomes (LIP) and vancomycin hydrochloride (VANKA) containing liposomes (VANKA-LIP) were prepared for each of the DSPC and Chol compositions. The aim of our study was to evaluate the effect of liposome composition on the VANKA encapsulation efficiency and release kinetics.

Abstract: The aim of the research was to evaluate the content of metallic elements in different parts of lingonberries (Vaccinium vitis-idaea L.) depending on their place of growth and evaluate the transfer factor values from between different parts of plants (fine roots, leaves, berries). Obtained results show that there are no significant differences between the content of Fe, Cu, Zn and K, and there are similar element transfer factors between different parts of lingonberries independent from which site the samples are taken.

Abstract: Quantitative analysis of catecholamines and their acidic metabolites can provide vital information for diagnosis and treatment of various diseases (such as adrenal tumors). However, complicated purification protocols are usually required to isolate the analytes. Molecularly imprinted polymers (MIPs) have attracted considerable attention as a method of selectively separating desired compounds from their matrix. Therefore, we propose a synthetic procedure for new molecularly imprinted sorbents that possess selective binding sites for both catecholamines and their acidic metabolites. The new polymer utilizes non-covalent and semi-covalent imprinting methods. The binding properties of MIPs were evaluated using chromatographic experiments. The results suggest that the MIPs bind with catecholamines much more selectively than with their acidic metabolites. Therefore, increasing sorption selectivity of the acids would make it possible to perform simultaneous extraction of both compound groups.

Abstract: The possibility to modify the morphology by crystallization additives of model substances was studied using molecular dynamics simulations. For this 2,6-dimethoxybenzoic acid and 3-hydroxybenzoic acid, each having two polymorphic forms, including a form without carboxylic acid homodimers in their crystal structure were selected. For each polymorph 2-3 largest crystal faces were selected for the study and the crystal was cut along these planes by preparing a simulation box with these planes facing towards solution containing additives. In the performed study it was evaluated which additives potentially can influence the crystal morphology and possibly also polymorph obtained in the crystallization by significantly changing the growth rate of crystal by adsorbing on the surface. For the study 4-5 additives providing different intermolecular interaction possibilities were selected. Among the studied additives urea showed the most complete adsorption and the longest residence time on surfaces of both substances, with the exceptions of few specific planes.

Abstract: The goal of this study was to evaluate the influence of birch outer bark (BOB) extraction solvents on the antioxidant properties of the obtained dry extracts, which were added in cosmetic product emulsions. Extracts obtained in ethanol, 2-propanol, 1-butanol and ethyl acetate as well as one purified in ethanol by means of recrystallization were used as antioxidant additives, in 30 and 60 mg·g^-1 concentrations, to cosmetic water-in-oil type emulsions. It was found that raw extracts had a considerably higher antioxidant stability than purified ones, because the raw extracts showed a higher phenolic compound content. The highest stability was detected in the cosmetic sample, which had a raw BOB extract obtained in 2-propanol. At the additive concentration of 60 mg·g^-1, the protection factor was 20.6 times higher than in the case of a blank sample. Among other solvents used, 2-propanol showed the best solubility for BOB extract phenolic compounds, the content of which reached 3.58 wt% from the oven dry extract. It could be concluded that raw BOB extracts act as an excellent antioxidant additive in cosmetic emulsions.

Abstract: The effect of water extracts obtained from bark of growing in Latvia and widely spread in Europe grey alder (Alnus incana), black alder (Alnus glutinosa) and aspen tree (Populus tremula), on the amylase activity in human saliva was evaluated. The extracts were obtained using advanced ACE equipment and distilled hot water as a solvent. The total yields of extractives from bark were rather similar and varied from 16 % to 21 % based on dry bark. However, the content of proantocianidine and salicine derivatives used as diagnostic characteristic for evaluation of effect of extracts on activity of amylase – a glucose-polymers cleavage enzyme - differed significantly. The results of in-vitro tests realized using the model of human gastrointestinal pass have shown that the abovementioned extracts in micro dosages are able to increase significantly activity of amylase. However, this effect is dose dependent and when the dose is exceeded the opposite effect – inhibition of amylase activity - is observed. This effect is explained by increasing of proantocianidins component in the volume of the tested extract dose, because pure proantocianidins, isolated from grey alder bark significantly inhibited activity of amylase. The further investigation is necessary in order to estimate effective and safe dosages for application of extracts providing a guaranteed unambiguous effect of activation or inhibition of amylase activity.

Abstract: When producing recombinant proteins with Pichia pastoris, cultivation parameters, such as induction temperature, dissolved oxygen level and residual methanol concentration play a crucial role in product biosynthesis and subsequent purification, therefore to maximize protein yields, the optimization of these parameters is imperative. Two different Pichia pastoris cultivation strategies for HBsAg VLP production in a 5 L stirred-tank bioreactor and the influence of different cultivation parameters on product yield were investigated. Residual methanol concentrations were controlled at low (>0.01 g/L), medium (1.5-2.0 g/L) and high (5.0-6.0 g/L) levels using a PI-based feed rate control algorithm based on the online methanol sensor signal. Product was purified using a novel and rapid purification method including steps of ammonium sulfate precipitation, size-exclusion chromatography and hydrophobic interaction chromatography. Employing an in-situ methanol sensor probe, the PI-based methanol feed rate control algorithm provided residual methanol concentration control with an average deviation of ±0.4 g/L from set-point value. Employing a cultivation protocol with an increased methanol concentration controlled at 6.0 g/L and a reduced DO level below 10 %, resulting in a final dry cell biomass concentration of 140 g/L and purified HBsAg VLPs yield of 186 mg/L. Developed purification method proved advantageous to other described methods, as it did not include time consuming extraction and centrifugation steps.

Abstract: The recent surge in interest in the densification of calcium phosphate powders needs consideration of all the influencing factors. Spark plasma sintering with the primary contribution from the spark plasma and cold compaction that densifies from the large compaction pressures were considered. X-ray diffraction and Fourier transform infra-red spectroscopy characterized the powder and tablet to confirm the retention of the amorphous phase. Density was measured using the Archimedes method and the microstructure was viewed by scanning electron microscopy. The densified tablets were indented by nanoindentation to determine the hardness and elastic modulus. Reports on the density showed that the smallest contribution to density arose from vacuum, a marginally higher densification from the spark plasma effect, but the largest densification arose from the use of significantly higher pressures. Nanoindentation showed a small difference in elastic modulus between tablets densified at 25 °C and 200 °C, but a larger difference in the hardness.

Abstract: Bone regeneration is complex physiological process, which include the most common form of regeneration - bone fracture healing and new bone formation. Moreover, large bone defects, infections and bone diseases such as osteoporosis and arthritis can impair bone regeneration. Despite intensive research and development of biomaterials for bone tissue engineering, especially for osteoporotic bone healing, the properties of the fabricated biomaterials are still far from those of unique composite structure of natural bone and desired therapeutic effect not achieved. This mini-review will highlight the various cutting-edge injectable inorganic-organic biocomposites as minimally invasive and regenerative therapeutics for bone tissue regeneration. The review will summarize the main strategic tools for the development of injectable biocomposites: natural or synthetic biopolymer-based hydrogels, bioactive inorganic fillers and biologically active components, as well as the fabrication techniques and synthesis methods.