crystals Editorial Green Approach in Synthesis of Bio-Inspired Materials Anamarija Stankovi´ c 1, * , Martina Medvidovi´ c-Kosanovi´ c 1 , Jasminka Kontrec 2 and Branka Njegi´ c Džakula 3   Citation: Stankovi´ c, A.; Medvidovi´ c- Kosanovi´ c, M.; Kontrec, J.; Džakula, B.N. Green Approach in Synthesis of Bio-Inspired Materials. Crystals 2021, 11, 1243. https://doi.org/10.3390/ cryst11101243 Received: 9 October 2021 Accepted: 13 October 2021 Published: 14 October 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional afﬁl- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Institute for General, Inorganic and Physical Chemistry and Teaching Methods in Chemistry, Department of Chemistry, Josip Juraj Strossmayer University of Osijek, Ulica Cara Hadrijana 8/A, 31000 Osijek, Croatia; martina.medvidovic@gmail.com 2 Laboratory for Precipitation Processes, Ru ¯ der Boškovi´ c Institute, Bijeniˇ cka c. 54, 10000 Zagreb, Croatia; Jasminka.Kontrec@irb.hr 3 Ru ¯ der Boškovi´ c Institute, Bijeniˇ cka c. 54, 10000 Zagreb, Croatia; bnjeg@irb.hr * Correspondence: ster.anamarija@gmail.com In this Special Issue, we focus on biomineralization/pathological biomineralization systems and the synthesis of bioinspired materials. This Special Issue promotes the cur- rent trend of “green chemistry”, and, as such, in all published papers, only aqueous solutions and eco-friendly additives were used for the production of well-characterized bioinspired materials. This Special Issue contains four papers: three original research papers and one review. Here, a brief introduction of these papers is provided. Kontrec et al. [1] in their paper indicate a signiﬁcant contribution of initial pH to the overall effect of all parameters relevant to precipitation processes and biomineraliza- tion. This paper reports on the inﬂuence of initial pH and type of stirring on the kinetics, phase composition, size, and morphology of spontaneously precipitated calcium carbonate (CaCO 3 ). CaCO 3 is one of the most widespread biominerals formed via biomineralization in calcifying organisms. Precipitation processes are the physicochemical basis of biominer- alization. The main parameter controlling the precipitation of CaCO 3 is supersaturation, but other parameters, such as the concentration of constituent ions and dissolved carbon dioxide (CO 2 )[2], the presence of additives [3,4], temperature [5], pH [6], ionic strength [7] and hydrodynamics [8], are also known to inﬂuence and control CaCO 3 precipitation and, consequently, together with the variety of biological constituents and processes, inﬂuence biomineralization. Bearing in mind that the supersaturation, ionic strength, and activity ra- tio of constituent ions a(Ca 2+ )/a(CO 3 2- ) inﬂuence the phase composition and morphology of the precipitated CaCO 3 , in the work presented in this paper, the initial values of these parameters in all experiments were identical. Amongst the sixty different types of biominerals, one of the most interesting to hu- mans is calcium phosphate (CaP), the main inorganic component of vertebrate skeletons, and it is also prominent in pathological biomineralization [9,10]. The inclusion of additives in the precipitation system affects the rate and mechanism of CaP formation as well as the properties of the formed solid phase(s). Erceg et al. [11] investigated the inﬂuence of different classes of amino acids (AAs), namely, charged (aspartic acid and lysine), polar (as- paragine and serine), and non-polar (phenylalanine) amino acids, under conditions similar to physiological conditions. The observed differences in the effects that AAs exert on CaP precipitation, as well as the differences in the behavior of AAs of the same class, indicated that classiﬁcation based on charge and polarity cannot satisfactorily explain the different effects. Rather, these relatively simple molecules should be studied as speciﬁc entities. The obtained results point to the likely complex role of AAs in biological mineralization but also to a rather simple method of controlling CaPs properties, which are of importance in the preparation of multifunctional bone regeneration materials. Urolithiasis is a multifactorial disease with a high incidence and high recurrence rate, characterized by formation of solid deposits in the urinary tract. Petrovi´ c et al. [12] Crystals 2021, 11, 1243. https://doi.org/10.3390/cryst11101243 https://www.mdpi.com/journal/crystals