Calcium Carbonate

3D printing nacre powder/sodium alginate scaffold loaded with PRF promotes bone tissue repair and regeneration

Bone defects are a common complication of bone diseases, which often affect the quality of life and mental health of patients. The use of biomimetic bone scaffolds loaded with bioactive substances has become a focal point in the research on bone defect repair. In this study, composite scaffolds resembling bone tissue were created using nacre powder (NP) and sodium alginate (SA) through 3D printing. These scaffolds exhibit several physiological structural and mechanical characteristics of bone tissue, such as suitable porosity, an appropriate pore size, applicable degradation performance and satisfying the mechanical requirements of cancellous bone, etc. Then, platelet-rich fibrin (PRF), containing a mass of growth factors, was loaded on the NP/SA scaffolds. This was aimed to fully maximize the synergistic effect with NP, thereby accelerating bone tissue regeneration. Overall, this study marks the first instance of preparing a bionic bone structure scaffold containing NP by 3D printing technology, which is combined with PRF to further accelerate bone regeneration. These findings offer a new treatment strategy for bone tissue regeneration in clinical applications.

Properties and mechanisms of steel slag strengthening microbial cementation of cyanide tailings

The advantages of microbial induced carbonate precipitation (MICP) as bio-cementation technology for tailings-solidification are under extensive investigation. In order to improve performance of bio-cementation, many strengthening materials were applied to the bio-cementation of tailings. Steel slag (SS) is a kind of industrial solid waste, its chemical composition and mineral composition are similar to cement, and it has a certain application prospect as an auxiliary cementing material. In this study, the properties and mechanism of SS strengthening MICP cementation of cyanide tailings (CT) were investigated. The results showed that Sporosarcina pasteurii growth is not inhibited by SS, and Sporosarcina pasteurii can promote the hydration reaction of SS, providing a suitable alkaline environment and Ca2+, promoting the production of more CaCO3 in the MICP process. When 200 mL of CT leachate was added 1.4 g SS (200-400 mesh), the adsorption of Cu, Pb, Zn, Cd, total cyanide (T-CN), and free cyanide (F-CN) reached 48.05%, 44.28%, 36.25%, 16.67%, 79.05%, and 67.20%, respectively. The maximum unconfined compressive strength（UCS） of the cemented body (with 5%, 150 mesh SS) was 1.97 MPa, which was 3.396 times as high as that without SS. The cemented body with the addition of SS (5%, 150 mesh) contained more carbonate bound Cu (2.75%), Pb (4.89%), Zn (5.37%), and Cd (5.75%), and less exchangeable Cu (3.65%), Pb (6.85%), Zn (2.27%), and Cd (4.42%) than that without SS. In summary, the addition of SS improved the UCS of cemented bodies and the stability of heavy metals and cyanide, reduced the environmental risks existing in the process of CT storage. Meanwhile, it also provides new ideas for resource utilization of industrial solid waste SS and improvement of mine filling materials.

Chiroptically Active Multi-Modal Calcium Carbonate-Based Nanocomposites

The development of multimodal nano- and micro-structures has become an increasingly popular area of research in recent years. In particular, the combination of two or more desirable properties within a single structure opens multiple opportunities from biomedicine, sensing, and catalysis, to a variety of optical applications. Here, for the first time, we report the synthesis and characterization of multimodal chiroptically active CaCO3 nanocomposites. These composites have been prepared by a modified microemulsion method in the presence of an amino acid (cysteine). Following this, additional modalities have been introduced by loading the composites with luminescent nanoparticles or doping with Eu3+ ions. The luminescent composites have been produced by the incorporation of CuInZnS/ZnS or CdSe@ZnS/ZnS core/shell quantum dots, or via doping with trivalent europium. In this manner, we have produced chiroptically active composites with orange, green, and red luminescence. Overall, this work demonstrates the unique advantage and potential of our approach and new class of chiroptically active CaCO3 nanocomposites, which display tunable functionality to specific requirements via the incorporation of desired ions, nanoparticles, and chirality of the structure.

Recombinant Collagen-Templated Biomineralized Synthesis of Biocompatible pH-Responsive Porous Calcium Carbonate Nanospheres

The synthesis of calcium carbonate with controlled morphology is crucial for its biomedical applications. In this study, we synthesized well-ordered porous calcium carbonate nanospheres using recombinant collagen as a biomineralization template. Porous collagen-calcium carbonate was created by incubating calcium chloride and sodium carbonate with collagen biotemplates at room temperature. Our results show that the recombinant collagen-calcium carbonate nanomaterials underwent a morphological transition from solid nanospheres to more porous nanospheres and a phase transformation from vaterite to a mixture of calcite and vaterite. This study highlights the crucial role of recombinant collagen in modulating the morphology and crystallinity of calcium carbonate nanoparticles. Importantly, the highly porous recombinant collagen-calcium carbonate hybrid nanospheres demonstrated superior loading efficacy for the model drug cefoperazone. Furthermore, the drug loading and releasing results suggest that hybrid nanospheres have the potential to be robust and biocompatible pH-responsive drug carriers. Our findings suggest that recombinant collagen's unique amino acid content and rodlike structure make it a superior template for biomineralized synthesis. This study provides a promising avenue for the production of novel organic-inorganic nanostructures, with potential applications in biomedical fields such as drug delivery.

In Vivo Immune Adjuvant Effects of CaCO3 Nanoparticles through Intracellular Ca2+ Concentration Regulation

Calcium (Ca) is a vital component of the human body and plays a crucial role in intracellular signaling and regulation as a second messenger. Recent studies have shown that changes in intracellular Ca2+ concentration can influence immune cell function. In this study, we developed calcium carbonate nanoparticles (CaNPs) of various sizes using a Nanosystem Platform to modulate intracellular Ca2+ concentration in vitro and in vivo. Our findings demonstrate that intravenous administration of CaNPs led to changes in the number and ratio of immune cells in the spleen and stimulated the activation of dendritic cells (DCs) and macrophages. Notably, CaNPs exhibited strong adjuvant properties in the absence of antigenic stimuli. These results indicate that CaNPs have the potential to regulate immune cell function by modulating Ca2+ concentrations, offering a novel approach for disease prevention and treatment in combination with antigens or drugs. Overall, our study emphasizes the importance of modulating intracellular Ca2+ concentration as a means of regulating immune cell function.

Effects of eggshell and seashell powder as natural dietary calcium supplements on growth, molting frequency, and carapace calcium composition of juvenile red claw crayfish, Cherax quadricarinatus

The growth performance of red claw crayfish, Cherax quadricarinatus, fed diets with different sources and concentrations of natural calcium was evaluated. Formulated diets containing 30% protein and 8% lipid were prepared using supplementation of 0 (control), 3%, 6%, 9% eggshell, and 6% seashell. C. quadricarinatus juveniles with an average total weight of 0.21 ± 0.01 g and length of 25.0 ± 0.10 mm were obtained from ten ovigerous females bred in captivity. An aquarium with a size of 0.72 m² was divided into eight compartments with an area of 0.09 m² per compartment and was individually stocked with juvenile crayfish. A total of eight juvenile crayfish were used per dietary treatment. There were five dietary treatments in total and each of these treatments were replicated three times. The addition of eggshell and seashell powder exerted positive effects on the growth performance, molting frequency, and survival of the crayfish. Crayfish fed with a 6% eggshell-supplemented diet exhibited the best overall growth performance. The calcium percentage of the carapace increased with the increase in calcium content of the diets. Meanwhile, the performance of diets comprising eggshells and seashells was not significantly different (P > 0.05). Considering the low cost and abundance of eggshells, the addition of 6% of this product to the diet is recommended for the best growth of juvenile C. quadricarinatus.

Nanoplastics Weathering and Polycyclic Aromatic Hydrocarbon Mobilization

Despite increasing efforts to recycle plastic materials, large quantities of plastics waste continue to accumulate in the oceans. Persistent mechanical and photochemical degradation of plastics in the oceans yields micro- and nanoscale plastic particles, which represent potential vectors for mobilizing hydrophobic carcinogens in an aqueous milieu. Yet, the fate and potential threats associated with plastics remain largely unexplored. Herein, we apply an accelerated weathering protocol to consumer plastics to characterize the effect of photochemical weathering on the size, morphology, and chemical composition of nanoplastics under defined conditions and validate that the photochemical degradation is consistent with plastics harvested from the Pacific Ocean. Machine learning algorithms trained with accelerated weathering data successfully classify weathered plastics from nature. We demonstrate that photodegradation of poly(ethylene terephthalate) (PET)-containing plastics produces enough CO₂ to induce a mineralization process that results in the deposition of CaCO₃ on nanoplastics. Finally, we determine that despite UV-radiation induced photochemical degradation and mineral deposition, nanoplastics retain their ability to sorb, mobilize, and increase bioaccessibility of polycyclic aromatic hydrocarbons (PAHs) in water and under simulated physiological gastric and intestinal conditions.

Polysaccharides as Effective and Environmentally Friendly Inhibitors of Scale Deposition from Aqueous Solutions in Technological Processes

In this paper, we consider natural and modified polysaccharides for use as active ingredients in scale deposition inhibitors to prevent the formation of scale in oil production equipment, heat exchange equipment, and water supply systems. Modified and functionalized polysaccharides with a strong ability to inhibit the formation of deposits of typical scale, such as carbonates and sulfates of alkaline earth elements found in technological processes, are described. This review discusses the mechanisms of the inhibition of crystallization using polysaccharides, and the various methodological aspects of evaluating their effectiveness are considered. This review also provides information on the technological application of scale deposition inhibitors based on polysaccharides. Special attention is paid to the environmental aspect of the use of polysaccharides in industry as scale deposition inhibitors.

CaCO3 from Anadara granosa shell as reparative dentin inducer in odontoblast pulp cells: In-vivo study

Introduction

Anadara granosa (blood clam) shell contained 98.7% of calcium carbonate (CaCO3). This material has bio-properties that able to induced the dentin regeneration. This study is expected to reveal the nuclear factor kappa beta (NF-kB), transforming growth factor beta (TGF-β1), and vascular endothelial growth factor A (VEGF-A) expression in dental pulp after application of CaCO3 from Anadara granosa shell.

Material and methods

The thirty Rattus norvegicus strain Wistar used as model. The maxillary first molar was preparation using 0.84 mm low-speed diamond bur to made cavity. The cavity then applied glass ionomer cement (as control group) and other group applied CaCO3 from Anadara granosa shell. The teeth in each group were extracted after 1st, 3rd and 7th days of application for immunohistochemistry analysis for NF-kB, TGF-β1, and VEGF-A expression.

Result

The NF-kB expression in the group with CaCO3 from Anadara granosa shell lower than control after 1st, 3rd and 7th days (p < 0.05). In other hand, the TGF-β1 and VEGF-A expression in the group with CaCO3 from Anadara granosa shell higher than control after 1st, 3rd and 7th days (p < 0.05).

Conclusion

CaCO3 from Anadara granosa shell able to stimulate the TGF-β1 and VEGF-A and suppress the NF-kB expression in the dental pulp. This material able to develop as dentin-pulp material restoration.

Valorization of tannery solid wastes for sustainable enzyme induced carbonate precipitation process

Biocementation via enzyme induced carbonate precipitation (EICP) is an emerging ground improvement technique that utilizes urease for calcium carbonate precipitation. Usage of expensive laboratory grade chemicals in EICP hinders its implementation at field level applications. In this study, the feasibility of utilizing solid wastes generated from leather industry was investigated for EICP process. Initially, the proteinaceous fleshing waste was used as nitrogen source for production of an extracellular urease from Arthrobacter creatinolyticus MTCC 5604 followed by its subsequent use in EICP with suspended solids of tannery lime liquor, as alternative calcium source. The calcium ion solution was prepared by treating suspended solids of lime liquor with 1 N HCl. The EICP was optimum with 1000 U of urease, 1.0 M urea and 1.0 M CaCl₂.2H₂O for test tube experiments. Sand solidification experiments under optimal conditions with five times addition of cementation solution yielded a maximum unconfined compressive strength (UCS) of 810 kPa with laboratory grade CaCl₂.2H₂O and 780 kPa with calcium from lime liquor. The crystalline phases and morphology of the CaCO₃ precipitate were analyzed by XRD, FTIR and SEM-EDX. The results showed the formation of more stable calcite in EICP with calcium obtained from lime liquor, while calcite and vaterite polymorphs were obtained with CaCl₂.2H₂O. Utilization of fleshing waste and lime liquor in EICP could reduce the pollution load and sludge formation that are generated during the pre-tanning operations of leather manufacturing. The results indicated the viability of process to achieve cost effective and sustainable biocementation for large scale applications.

Preparation of calcium carbonate microrods from the gypsum scale layer of evaporation equipment

The difficult-to-remove CaSO₄ scale layer attached to an evaporator wall is a major problem in related industries. How to efficiently remove the CaSO₄ scale layer and convert it into fine chemicals with high added value, so as to turn waste into treasure, is a current research hotspot. In this study, a CaSO₄ scale layer was removed by 15 min rotary washing via a phase transfer route. Further, using the eluted calcium gluconate solution as a raw material and polyethylene glycol as the crystal control agent, CaCO₃ was prepared by a CO₂ carbonization method. The preparation conditions of CaCO₃ were optimized by single factor experiments, and the phase and morphology of the prepared samples were characterized by XRD and FESEM. The results show that the optimized conditions are as follows: reaction temperature 80 °C, reaction time 1 h, polyethylene glycol addition 3%, and a stirring rate of 400 rpm. The samples prepared under these conditions are pure-phase calcite-type CaCO₃ microrods with lengths of 1–2 μm and diameters of 300–500 nm.

The difficult-to-remove CaSO₄ scale layer attached to an evaporator wall is a major problem in related industries.

Integrating waste fish scale-derived gelatin and chitosan into edible nanocomposite film for perishable fruits

Petroleum-based plastics (such as polyethylene, polypropylene, polyvinyl chloride, polystyrene, etc.) as white waste have caused great concern in the environment. It is urgent to develop a kind of biodegradable, biocompatible and non-toxic materials to replace them. Herein, an environmental-friendly edible film for postharvest fruits refreshing application was prepared by combining the waste fish scale-derived gelatin, chitosan as well as CaCO₃ nanoparticles. The as-prepared nanocomposite film showed the multifunctional features, such as UV absorption, antimicrobial, oxygen screening, excellent mechanical properties and non-toxic. In addition, the protein-polysaccharide based nanocomposite film was hydrophilic and can be easily washed away on fruits before eating. In order to inspect its preservative effect on fruits, longan and banana were chosen as the testing object. Our results showed that the edible multifunctional nanocomposite film can effectively extend the shelf life of longan by more than 3 days and banana by more than 5 days, compared with the control groups. Integrating natural biological macromolecules gelatin and chitosan into a multifunctional nanocomposite film with series of advantages of biodegradability, sustainability as well as multifunction is expected to be a potential preservative material for food packaging applications.

Extraction of Value-Added Minerals from Various Agricultural, Industrial and Domestic Wastes

Environmental pollution is one of the major concerns throughout the world. The rise of industrialization has increased the generation of waste materials, causing environmental degradation and threat to the health of living beings. To overcome this problem and effectively handle waste materials, proper management skills are required. Waste as a whole is not only waste, but it also holds various valuable materials that can be used again. Such useful materials or elements need to be segregated and recovered using sustainable recovery methods. Agricultural waste, industrial waste, and household waste have the potential to generate different value-added products. More specifically, the industrial waste like fly ash, gypsum waste, and red mud can be used for the recovery of alumina, silica, and zeolites. While agricultural waste like rice husks, sugarcane bagasse, and coconut shells can be used for recovery of silica, calcium, and carbon materials. In addition, domestic waste like incense stick ash and eggshell waste that is rich in calcium can be used for the recovery of calcium-related products. In agricultural, industrial, and domestic sectors, several raw materials are used; therefore, it is of high economic interest to recover valuable minerals and to process them and convert them into merchandisable products. This will not only decrease environmental pollution, it will also provide an environmentally friendly and cost-effective approach for materials synthesis. These value-added materials can be used for medicine, cosmetics, electronics, catalysis, and environmental cleanup.

Geochemical Characterization of the NWA 11273 Lunar Meteorite Using Nondestructive Analytical Techniques: Original, Shocked, and Alteration Mineral Phases

A lunar feldspathic breccia meteorite, the Northwest Africa (NWA) 11273, was analyzed to compensate the lack of scientific data available about its mineralogy and geochemistry. In order to obtain a deeper characterization of the sample, a strategy based on the combination of nondestructive spectroscopic techniques such as X-ray fluorescence and Raman spectroscopy is used. Both techniques are being used in spatial missions by the Perseverance Rover, so their combination in the laboratory is here proposed as an optimal strategy to study the complete mineralogy of the sample. In addition to finding the minerals indicated by the Meteoritical Society (anorthite, olivine, pyroxene, kamacite, and troilite), other minor minerals were identified, such as zircon and ilmenite, which are minerals related to the Moon geology, as well as calcite and sulfate which can be considered products of terrestrial weathering. Finally, secondary minerals related to alteration processes were also found, such as hematite, quartz, and anatase. In this work, the alteration processes that gave rise to the detected secondary minerals have been proposed.

Whey as an Alternative Nutrient Medium for Growth of Sporosarcina pasteurii and Its Effect on CaCO3 Polymorphism and Fly Ash Bioconsolidation

Whey in large quantities can cause environmental problems when discarded, because it reduces dissolved oxygen and aquatic life. Nonetheless, it could be used as an easily available and economical alternative to reduce culture medium costs in microbially induced calcium carbonate precipitation (MICP). In this work, a native Sporosarcina pasteurii was isolated and then cultured by using different proportions of whey (W) in nutrient broth (NB). The solids were characterized by XRD, FT-IR, TGA, and SEM. The potential applications in bioconsolidation were also studied. Whey concentration was directly related to CaCO₃ production. Higher whey concentrations reduced calcium carbonate purity to nearly 80%. All experiments showed calcite and vaterite fractions, where a whey increment in the media increased calcite content and decreased vaterite content, causing a decrease in crystal size. MICP improved compressive strength (CS) in sand and fly ash. The best CS results were obtained by fly ash treated with 25 W-75 NB (37.2 kPa) and sand with 75 W-25 NB (32.1 kPa). Whey changed crystal polymorphism in biogenic CaCO₃ production. Material bioconsolidation depends on the CaCO₃ polymorph, thus fly ash was effectively bioconsolidated by crystallization of vaterite and sand by crystallization of calcite.

The Processing of Calcium Rich Agricultural and Industrial Waste for Recovery of Calcium Carbonate and Calcium Oxide and Their Application for Environmental Cleanup: A Review

Every year a million tonnes of calcium rich agro and industrial waste are generated around the whole globe. These calcium rich waste like finger citron, shells of cockle, mussel, oysters etc., and egg shell are biological sources which have various organic compounds. The inorganic calcium rich waste includes gypsum, dolomite, sludge etc., which are produced in surplus amount globally. Most of these by-products are mainly dumped, while few are used for land-filling purposes which leads to the pollution. These agro and industrial by-products could be processed for the recovery of calcium carbonate and calcium oxide particles by physical and chemical method. The recovery of calcium carbonate and calcium oxide particles from such by products make them biocompatible. Moreover, the products are economical due to their synthesis from waste materials. Here, in this current review work we have emphasized on the all the calcium rich agro industries and industrial by products, especially their processing by various approaches. Further, we have also focused on the properties and application of such calcium carbonate and oxide particles for the remediation of organic and inorganic pollutants from the environments. The recovery of such particles from these byproducts is considered not only economical and eco-friendly but it also minimizes the pollution present in the form of solid waste.

Synthesis and characterizations of natural limestone-derived nano-hydroxyapatite (HAp): a comparison study of different metals doped HAps on antibacterial activity

Earth-abundant mineral limestone obtained from North Sumatera, Indonesia, has been utilized to synthesize nano-hydroxyapatite (HAp). Although HAp is biocompatible to the human bone, its antibacterial activity is still very low. Herein, different metal ions (i.e., Ag, Cu, Zn, and Mg) were doped into HAp to improve the antibacterial activity. The as-synthesized HAp was characterized by X-ray ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), energy disperse spectroscopy (EDS), Fourier transmission infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET). The antibacterial test showed that the performance of HAp to inactivate bacterial growth was significantly improved after incorporating the metal ion dopants into HAp. Ag-HAp exhibited the highest activity toward E. coli and S. aureus with an antibacterial rate of 99.9 ± 0.1%, followed by Zn-HAp, Cu-HAp, and Mg-HAp.

Antibacterial activities of different metal ion doped HAp towards (a) E. coli and (b) S. aureus bacteria.

Innovative Gas-Liquid Membrane Contactor Systems for Carbon Capture and Mineralization in Energy Intensive Industries

CO₂ mineralization is an alternative to conventional geological storage and results in permanent carbon storage as a solid, with no need for long-term monitoring and no requirements for significant energy input. Novel technologies for carbon dioxide capture and mineralization involve the use of gas-liquid membrane contactors for post-combustion capture. The scope of the present study is to investigate the application of hollow fiber membrane contactor technology for combined CO₂ capture from energy-intensive industry flue gases and CO₂ mineralization, in a single-step multiphase process. The process is also a key enabler of the circular economy for the cement industry, a major contributor in global industrial CO₂ emissions, as CaCO₃ particles, obtained through the mineralization process, can be directed back into the cement production as fillers for partially substituting cement in high-performance concrete. High CO₂ capture efficiency is achieved, as well as CaCO₃ particles of controlled size and crystallinity are synthesized, in every set of operating parameters employed. The intensified gas-liquid membrane process is assessed by calculating an overall process mass transfer coefficient accounting for all relevant mass transfer resistances and the enhanced mass transfer due to reactive conditions on the shell side. The obtained nanocomposite particles have been extensively characterized by DLS, XRD, TGA, SEM, TEM, and FTIR studies, revealing structured aggregates (1–2 μm average aggregate size) consisting of cubic calcite when the contactor mode is employed.

Cyanobacterial Mats in Calcite-Precipitating Serpentinite-Hosted Alkaline Springs of the Voltri Massif, Italy

(1) Background: Microbial communities in terrestrial, calcifying high-alkaline springs are not well understood. In this study, we investigate the structure and composition of microbial mats in ultrabasic (pH 10–12) serpentinite springs of the Voltri Massif (Italy). (2) Methods: Along with analysis of chemical and mineralogical parameters, environmental DNA was extracted and subjected to analysis of microbial communities based upon next-generation sequencing. (3) Results: Mineral precipitation and microbialite formation occurred, along with mat formation. Analysis of the serpentinite spring microbial community, based on Illumina sequencing of 16S rRNA amplicons, point to the relevance of alkaliphilic cyanobacteria, colonizing carbonate buildups. Cyanobacterial groups accounted for up to 45% of all retrieved sequences; 3–4 taxa were dominant, belonging to the filamentous groups of Leptolyngbyaceae, Oscillatoriales, and Pseudanabaenaceae. The cyanobacterial community found at these sites is clearly distinct from creek water sediment, highlighting their specific adaptation to these environments.

Novel method to achieve crystallinity of calcite by Bacillus subtilis in coupled and non-coupled calcium-carbon sources

Bacteria mineralization is a promising biotechnological approach to apply in biomaterials development. In this investigation, we demonstrate that Bacillus subtilis 168 induces and influences CaCO₃ composites precipitation. Crystals were formed in calcium-carbon non-coupled (glycerol + CaCl₂, GLY; or glucose + CaCl₂, GLC) and coupled (calcium lactate, LAC; or calcium acetate, ACE) agar-sources, only maintaining the same Ca²⁺ concentration. The mineralized colonies showed variations in morphology, size, and crystallinity form properties. The crystals presented spherulitic growth in all conditions, and botryoidal shapes in GLC one. Birefringence and diffraction patterns confirmed that all biogenic carbonate crystals (BCC) were organized as calcite. The CaCO₃ in BCC was organized as calcite, amorphous calcium carbon (ACC) and organic matter (OM) of biofilm; all of them with relative abundance related to bacteria growth condition. BCC-GLY presented greatest OM composition, while BCC-ACE highest CaCO₃ content. Nucleation mechanism and OM content impacted in BCC crystallinity.

Enhancement of Biomass and Calcium Carbonate Biomineralization of Chlorella vulgaris through Plackett-Burman Screening and Box-Behnken Optimization Approach

The biosynthesis of calcium carbonate (CaCO₃) minerals through a metabolic process known as microbially induced calcium carbonate precipitation (MICP) between diverse microorganisms, and organic/inorganic compounds within their immediate microenvironment, gives rise to a cementitious biomaterial that may emerge as a promissory alternative to conventional cement. Among photosynthetic microalgae, Chlorella vulgaris has been identified as one of the species capable of undergoing such activity in nature. In this study, response surface technique was employed to ascertain the optimum condition for the enhancement of biomass and CaCO₃ precipitation of C. vulgaris when cultured in Blue-Green (BG)-11 aquaculture medium. Preliminary screening via Plackett–Burman Design showed that sodium nitrate (NaNO₃), sodium acetate, and urea have a significant effect on both target responses (p < 0.05). Further refinement was conducted using Box–Behnken Design based on these three factors. The highest production of 1.517 g/L C. vulgaris biomass and 1.143 g/L of CaCO₃ precipitates was achieved with a final recipe comprising of 8.74 mM of NaNO₃, 61.40 mM of sodium acetate and 0.143 g/L of urea, respectively. Moreover, polymorphism analyses on the collected minerals through morphological examination via scanning electron microscopy and crystallographic elucidation by X-ray diffraction indicated to predominantly calcite crystalline structure.

Porous Alginate Scaffolds Assembled Using Vaterite CaCO3 Crystals

Formulation of multifunctional biopolymer-based scaffolds is one of the major focuses in modern tissue engineering and regenerative medicine. Besides proper mechanical/chemical properties, an ideal scaffold should: (i) possess a well-tuned porous internal structure for cell seeding/growth and (ii) host bioactive molecules to be protected against biodegradation and presented to cells when required. Alginate hydrogels were extensively developed to serve as scaffolds, and recent advances in the hydrogel formulation demonstrate their applicability as "ideal" soft scaffolds. This review focuses on advanced porous alginate scaffolds (PAS) fabricated using hard templating on vaterite CaCO3 crystals. These novel tailor-made soft structures can be prepared at physiologically relevant conditions offering a high level of control over their internal structure and high performance for loading/release of bioactive macromolecules. The novel approach to assemble PAS is compared with traditional methods used for fabrication of porous alginate hydrogels. Finally, future perspectives and applications of PAS for advanced cell culture, tissue engineering, and drug testing are discussed.

Marble-derived microcalcite improves bone healing in mice osteotomy

Approximately 10% of all fractures result in delayed healing or non-unions. Bone healing can be improved by the application of osteoconductive and osteoinductive biomaterials. Microcalcite (MCA) as a naturally available calcium carbonate-based biomaterial derived from marble may have the potential to improve bone healing. Herein, we studied for the first time, if MCA in combination with platelet-rich plasma (PRP) can be used as a bone graft material for bone healing in vivo. For this purpose, osteotomies were induced in CD-1 mice (n = 60). Animals received into the osteotomy gap either MCA-loaded PRP (MCA + PRP; n = 20), PRP alone (PRP; n = 20) or no application (NONE; n = 20). Bone healing was evaluated at two and five weeks after osteotomy by micro-computed tomography (μCT), histomorphometric, immunohistochemical and Western Blot analyses. μCT of MCA + PRP femurs revealed more bone volume and an increased polar moment of inertia, indicating a higher biomechanical stability when compared to PRP and NONE femurs. Histomorphometry revealed an increased total callus area after two weeks and a reduced callus tissue area after five weeks in MCA + PRP and PRP animals compared to NONE animals, indicating an accelerated process of bone healing and remodeling over the study period. Moreover, histomorphometric analyses demonstrated an increased fraction of osseous tissue within the callus in MCA + PRP femurs when compared to PRP and NONE femurs. Immunohistochemical analyses showed increased numbers of Ki67⁺ cells in callus tissue of MCA + PRP femurs. Of interest, Western Blotting revealed a significantly reduced expression of BMP-4 in MCA + PRP animals, while the expression of BMP-2 did not reveal any significant differences between the groups. This indicates a modified balance between angiogenesis and osteogenesis due to MCA. In conclusion, the application of MCA with PRP improved bone healing in a murine osteotomy model and, thus, might be a promising novel bone graft material which may be of interest for clinical fracture treatment.

Mechanochemical synthesis of hydroxyapatite using cuttlefish bone and chicken eggshell as calcium precursors

This work explores the possibility of synthesising hydroxyapatite via mechanochemical route using biogenic calcium carbonate sources, namely calcite in chicken eggshell and aragonite in cuttlebone. The calcium source and orthophosphoric acid in ratio complying with Ca/P = 1.67 were submitted to high-energy ball milling with transferred energy values in the 1.6 to 123.0 kWh/g range, in the presence of 6.4 wt% water. Results show that increasing transferred energy results in CaCO₃ → DCPD → HA reaction sequence when the used calcium source is cuttlebone, and in CaCO₃ → DCPD → DCPA → HA when eggshell is used. The produced calcium orthophosphates exist in delimited energy transfer ranges; HA forms monophasic regions at the highest transferred energy ranges tested. 52.5 kWh/g is the minimum energy value for hydroxyapatite formation starting from eggshell, while only 6.2 kWh/g is required starting from cuttlebone. Calcium orthophosphate dimensionality depends on the supplied energy and on the starting CaCO₃ polymorph, and includes nanospheres and nanoplates, and more complex flower-like geometries built from individual nanoparticles. Milling maps were built to systematise the effect of initial CaCO₃ polymorph and transferred milling energy on the conditions for hydroxyapatite mechanochemical formation. Obtained results demonstrate the potential of chicken eggshell and cuttlefish bone as natural precursors to produce hydroxyapatite, and the ability of high-energy milling as the corresponding processing route. This indicates an opportunity window for the development of reliable, scalable, fast and cost-effective HA production method.

A trypsin–calcium carbonate hybrid nanosphere based enzyme reactor with good stability and reusability

Trypsin not only acts as a novel robust biotemplate to mediate the growth of CaCO₃ crystals, but also enhances their biological properties as an excellent enzyme.