Publications by authors named "Kristaps Rubenis"

The eggshell membrane (ESM), resembling the extracellular matrix (ECM), acts as a protective barrier against bacterial invasion and offers various biofunctions due to its porous structure and protein-rich composition, such as ovalbumin, ovotransferrin, collagen, soluble protein, and antimicrobial proteins. However, the structure of ESM primarily comprises disulfide bonds and heterochains, which poses a challenge for protein solubilization/extraction. Therefore, the method of dissolving and extracting bioactive protein components from ESM has significant potential value and importance for exploring the reuse of egg waste and environmental protection.

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Nanocomposite hydrogels are suitable in bone tissue engineering due to their resemblance with the extracellular matrix, ability to match complex geometries, and ability to provide a framework for cell attachment and proliferation. The nanocomposite hydrogel comprises organic and inorganic counterparts. Gelatin methacrylate (GELMA) is an extensively used organic biomaterial in tissue engineering due to its excellent biocompatibility, biodegradability, and bioactivity.

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This study investigates osteoblastic cell spheroid cultivation methods, exploring flat-bottom, U-bottom, and rotary flask techniques with and without amorphous calcium phosphate (ACP) supplementation to replicate the 3D bone tissue microenvironment. ACP particles derived from eggshell waste exhibit enhanced osteogenic activity in 3D models. However, representative imaging of intricate 3D tissue-engineered constructs poses challenges in conventional imaging techniques due to notable scattering and absorption effects in light microscopy, and hence limited penetration depth.

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Xenografts are commonly used for bone regeneration in dental and orthopaedic domains to repair bone voids and other defects. The first-generation xenografts were made through sintering, which deproteinizes them and alters their crystallinity, while later xenografts are produced using cold-temperature chemical treatments to maintain the structural collagen phase. However, the impact of collagen and the crystalline phase on physicochemical properties have not been elucidated.

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Octacalcium phosphate (OCP) has excellent bone formation ability and a good resorption rate as compared to the commercial bone substitutes [, Bio-Oss (Geistlich Pharma AG) and MBCP+ (Biomatlante)], as well as synthesized biomaterials (hydroxyapatite and tricalcium phosphate). The synthesis approach to obtain phase-pure OCP possesses a great challenge due to its complex reaction mechanism and narrow synthesis window. Thus, the current study aimed to overcome the synthesis challenges and to define the precise reaction conditions required for controllable and reproducible synthesis of OCP.

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As the primary solid phase, amorphous calcium phosphate (ACP) is a pivotal precursor in cellular biomineralization. The intrinsic interplay between ACP and Howard factor underscores the significance of understanding their association for advancing biomimetic ACP development. While organic compounds play established roles in biomineralization, this study presents the synthesis of ACP with naturally occurring organic compounds (ascorbate, glutamate, and itaconate) ubiquitously found in mitochondria and vital for bone remodeling and healing.

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Amorphous calcium phosphate (ACP) is the first solid phase precipitated from a supersaturated calcium phosphate solution. Naturally, ACP is formed during the initial stages of biomineralization and stabilized by an organic compound. Carboxylic groups containing organic compounds are known to regulate the nucleation and crystallization of hydroxyapatite.

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Bone is a composite material made up of inorganic and organic counterparts. Most of the inorganic counterpart accounts for calcium phosphate (CaP) whereas the major organic part is composed of collagen. The interfibrillar mineralization of collagen is an important step in the biomineralization of bone and tooth.

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Calcium phosphate (CaP) biomaterials are extensively used to reconstruct bone defects. They resemble a chemical similarity to the inorganic mineral present in bones. Thus, they are termed as the key players in bone regeneration.

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Understanding photochromicity is essential for developing new means of modulating the optical properties and optical response of materials. Here, we report on the synthesis and exciting new photochromic behavior of Nb doped TiO nanoparticle colloids (NCs). We find that, in hole scavenging media, Nb doping significantly improves the photochromic response time of TiO nanoparticles.

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Donor dopants in oxide semiconductors are compensated not only by valuable electrons but also by other point defects, leading to a decrease in electric conductivity and infrared absorption. We demonstrate that the electron compensation mechanism in Ga doped ZnO nanocrystals can be promoted by photodoping. Unexpectedly, the electrons from photodoping are stable in the open air for months.

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