Tissue engineering and cell therapy are very attractive in terms of potential applications but remain quite challenging regarding the clinical aspects. Amongst the different strategies proposed to facilitate their implementation in clinical practices, biodegradable microparticles have shown promising outcomes with several advantages and potentialities. This critical review aims to establish a survey of the most relevant materials and processing techniques to prepare these micro vehicles. Special attention will be paid to their main potential applications, considering the regulatory constraints and the relative easiness to implement their production at an industrial level to better evaluate their application in clinical practices.

Biodegradable polyester/hydroxyapatite microparticles are widely proposed as microcarriers for drug/cell delivery or scaffolds for bone tissue regeneration. The current research implements the surfactant-free approach for the fabrication of polyester-based microparticles filled with hydroxyapatite nanoparticles (nHA) via the oil/water Pickering emulsion solvent evaporation technique for the first time, to the best of our knowledge. The process of polyester microparticle fabrication using nHA for the oil/water interface stabilization was studied as a function of phase used for nHA addition, which allows the preparation of a range of microparticles either filled with nHA or having it as a shell over the polymeric core. The effect of processing conditions (polymer nature, polymer/nHA ratio, ultrasound treatment) on particles’ total yield, size distribution, surface and volume morphology, and chemical structure was analyzed using SEM, EDX, Raman spectroscopy, and mapping. Addition of nHA either within the aqueous or oil phase allowed the effective stabilization of the oil/water interface without additional molecular surfactants, giving rise to hybrid microparticles in which total yield, size distribution, and surface morphology depended on all studied processing conditions. Preliminary ultrasound treatment of any phase before the emulsification process led to a complex effect but did not affect the homogeneity of nHA distribution within the polymeric core of the hybrid microparticles.

A brief review of the physiology of conditionally essential trace elements and their status among vegetarians and vegans is presented. To date, the biological role of conditionally essential trace elements has been studied much worse than the role of essential trace elements and, especially, macroelements. Nevertheless, they perform a number of important functions in the human body, and the development of their deficiency may lead to unpleasant consequences. Fluorine plays an important role in calcium-phosphorus metabolism and bone tissue development. In addition, it is necessary to maintain normal oral flora. With its deficiency, the risk of osteoporosis development increases while the resistance of tooth enamel to bacterial damage decreases. Despite the evidence that vegetarians are more likely to develop caries than omnivores, it is premature to conclude that they are poorly supplied with fluoride, primarily because drinking water is still the main source of fluoride. The most studied function of silicon is its involvement in the collagen synthesis. Thus, with silicon defi-ciency, the formation of connective tissue, including the organic matrix of the bones, is disturbed. Despite the fact that silicon is mainly found in plant foods, vegans should be mindful about its status, since they have an increased risk of osteopenia and osteoporosis. There is a lack of data on the physiological significance of bromine. Presumably, it is involved in the activa-tion of certain digestive enzymes, inhibitory processes in the nervous system. Although vegetarians and vegans seem to consume less bromine than omnivores, they are probably at a higher risk of intoxication with this element. This is due to the fact that bromine-containing pesticides are actively used in agriculture and can accumulate in plants. Vegetarians and vegans consume more plant foods. The situation is aggravated by the fact that bromine accumulates more actively against the background of iodine deficiency, which is often observed in these population groups. Boron plays a role in the glucose and lipid metabolism, as well as in the vitamin D, calcium and phosphates exchange, thus participating in the formation of an inorganic matrix of bones. It is unlikely that vegetarians and vegans have an increased risk of developing nutritional deficiency of boron compared to omnivores. However, considering data on a higher risk of vitamin D and calcium deficiency and osteoporosis, monitoring and correction of boron status can affect the prevalence of metabolic disturbances in bone tissue among vegans.

Представлен краткий обзор физиологии металлов, относящихся к условно-эссенциальным ультрамикроэлементам и обеспеченности ими вегетарианцев (людей, не употребляющих мясо и рыбу) и веганов (тех, кто полностью исключил продукты животного происхождения из рациона). Данные о физиологической роли условно-эссенциальных ультрамикроэлементов на сегодняшний день очень ограничены. Тем не менее известно о некоторых важных функциях, которые выполняют эти элементы, позволяющих отнести их к группе условно эссенциальных. Никель принимает участие в гемопоэзе, передаче сигнала инсулина. Больше известно о его токсических эффектах. Так как никель содержится преимущественно в растительной пище, веганы и вегетарианцы потребляют большие его количества. Более того, биодоступность никеля существенно повышается на фоне дефицита метионина, кальция, железа, цинка и селена, что часто встречается среди веганов. Наиболее изученным эффектом лития является его потенцирование тормозной активности магния в центральной нервной системе. Литий также используется в терапии маниакальных состояний. Поступает литий в основном с растительной пищей, однако при адекватной обеспеченности калием способность организма аккумулировать литий значительно снижается. Ванадий повышает чувствительность клеток к инсулину, участвует во внутриклеточном транспорте глюкозы. Дефицит ванадия сопровождается нарушением углеводного и липидного обмена, отягощает течение сахарного диабета 2-го типа. Пищевыми источниками ванадия являются в основном растительные и морепродукты. Согласно имеющимся данным, содержание ванадия в рационе веганов и вегетарианцев сравнимо с содержанием этого элемента у людей со смешанным питанием. Роль германия в организме изучена крайне плохо. Он входит в состав цитохромоксидазы и карбоангидразы. Есть свидетельства, что германий участвует в регуляции экспрессии генов, гемопоэзе, а также имеет противовоспалительную и иммуномодулирующую активность. Обеспеченность населения этим элементом также изучена недостаточно. По имеющимся данным, германий распределен в пищевых продуктах довольно однородно.

Acknowledgments were not included in the original publication