Three-dimensional cell-laden collagen scaffolds: From biochemistry to bone bioengineering.

The bones can be viewed as both an organ and a material. As an organ, the bones give structure to the body, facilitate skeletal movement, and provide protection to internal organs. As a material, the bones consist of a hybrid organic/inorganic three-dimensional (3D) matrix, composed mainly of collagen, noncollagenous proteins, and a calcium phosphate mineral phase, which is formed and regulated by the orchestrated action of a complex array of cells including chondrocytes, osteoblasts, osteocytes, and osteoclasts. The interactions between cells, proteins, and minerals are essential for the bone functions under physiological loading conditions, trauma, and fractures. The organization of the bone's organic and inorganic phases stands out for its mechanical and biological properties and has inspired materials research. The objective of this review is to fill the gaps between the physical and biological characteristics that must be achieved to fabricate scaffolds for bone tissue engineering with enhanced performance. We describe the organization of bone tissue highlighting the characteristics that have inspired the development of 3D cell-laden collagenous scaffolds aimed at replicating the mechanical and biological properties of bone after implantation. The role of noncollagenous macromolecules in the organization of the collagenous matrix and mineralization ability of entrapped cells has also been reviewed. Understanding the modulation of cell activity by the extracellular matrix will ultimately help to improve the biological performance of 3D cell-laden collagenous scaffolds used for bone regeneration and repair as well as for in vitro studies aimed at unravelling physiological and pathological processes occurring in the bone.

Starch modification through environmentally friendly alternatives: a review.

Starch is a versatile and a widely used ingredient, with applications in many industries including adhesive and binding, paper making, corrugating, construction, paints and coatings, chemical, pharmaceutical, textiles, oilfield, food and feed. However, native starches present limited applications, which impairs their industrial use. Consequently, starch is commonly modified to achieve desired properties. Chemical treatments are the most exploited to bring new functionalities to starch. However, those treatments can be harmful to the environment and can also bring risks to the human health, limiting their applications. In this scenario, there is a search for techniques that are both environmentally friendly and efficient, bringing new desired functionalities to starches. Therefore, this review presents an up-to-date overview of the available literature data regarding the use of environmentally friendly treatments for starch modification. Among them, we highlighted an innovative chemical treatment (ozone) and different physical treatments, as the modern pulsed electric field (PEF), the emerging ultrasound (US) technology, and two other treatments based on heating (dry heating treatment - DHT, and heat moisture treatment - HMT). It was observed that these environmentally friendly technologies have potential to be used for starch modification, since they create materials with desirable functionalities with the advantage of being categorized as clean label ingredients.

Dry heating treatment: A potential tool to improve the wheat starch properties for 3D food printing application.

The futuristic technology of three-dimensional (3D) printing is an additive manufacturing that allows obtaining creative and personalized food products. In this context, the study of food formulations (named as "inks") to be processed through 3D printing is necessary. This work investigated the use of dry heating treatment (DHT), a simple and safe method, to improve the wheat starch properties aiming to produce hydrogels to be used as "inks" for 3D printing. Wheat starch was processed by dry heating for 2 (DHT_2h) and 4 h (DHT_4h) at 130 °C. Modified wheat starches showed an increase in granule size, but processing did not alter the granule's shape nor surface, neither alter the molecular functional groups. On the other hand, DHT promoted slight molecular depolymerization, and reduction of starch crystallinity. Hydrogels "inks" based on the modified starches showed lower peak apparent viscosity during pasting, higher structural strength at rest, higher resistance to external stresses, higher gel firmness, and lower syneresis than hydrogels based on native starch. The hydrogels based on starch DHT_4h showed the best printability (greater ability to make a 3D-object by layer-by-layer deposition and to support its structure once printed) and this "ink" showed better reproducibility. Another point observed is that DHT extended the texture possibilities of printed samples based on wheat starch hydrogels. These results suggested that DHT is a relevant process to improve the properties of hydrogels based on wheat starch, making this ink suitable for 3D printing application.

Preparation of cassava starch hydrogels for application in 3D printing using dry heating treatment (DHT): A prospective study on the effects of DHT and gelatinization conditions.

3D printing is a technology capable of presenting creative, unique and intricate items in an attractive format, with specific compositions. However, novel ingredients must be developed to satisfy this new technological requirement. This work proposes dry heating treatment (DHT), a simple physical technique, as a method for modifying cassava starch, with particular focus on its use for 3D printing. DHT processing was conducted at 130 °C for 2 and 4 h (named DHT_2h and DHT_4h, respectively). Different gelatinization conditions (65, 75, 85, and 95 °C) were applied, and the hydrogels were evaluated considering different storage periods (1 and 7 days). Cassava starch properties were evaluated, focusing on the application of its hydrogels to 3D printing. The increase of DHT time produced a starch with higher carbonyl content and bigger granule size. It also reduced the water absorption index, increased the water solubility index, affected granule crystallinity and reduced molecular size. The longest storage period increased gel firmness. Increasing the temperature used in the gelatinization process reduced the gel strength of the native and DHT_2h. DHT_4h showed the lowest peak apparent viscosity and provided the strongest gels for all the evaluated conditions. Gels produced with DHT starches exhibited better printability than the native starch, mainly for the DHT_4h. This treatment was chosen to print 3D stars, and displayed better resolution than the native gels. Therefore, by using DHT, it was possible to obtain hydrogels with enhanced pasting properties, gel texture, and printability, thereby expanding the potential of applying cassava starch to 3D printing.

Hydrogels based on ozonated cassava starch: Effect of ozone processing and gelatinization conditions on enhancing 3D-printing applications.

Ozone is an interesting alternative for modifying starch, as it is considered an emerging and environmentally friendly technology. New applications for food ingredients are receiving attention, such as 3D printing. Consequently, the impact of emerging technologies on new applications must be understood. In this work, cassava starch was modified by ozone to evaluate its printability. Increasing ozonation time produced a starch with higher carbonyl and carboxyl contents, lower pH and molecular size, and gels with different behaviors (stronger and weaker than the native ones, as a function of processing time). The hydrogels obtained were evaluated in relation to pasting and gel properties, including their printability. The effects of starch concentration, gelatinization temperature and storage period were also evaluated. Starch ozonated for 30 min showed the lowest peak apparent viscosity at all the temperatures and starch concentrations evaluated, and provided the strongest gel. Gels produced by native starches and starches ozonated for 30 min showed good printability when the gelatinization temperature used was 65 °C, but up to this temperature, only starch ozonated for 30 min produced gels with good printability. This work highlights that, by using the ozone process to modify starch and varying the process conditions, it is possible to obtain hydrogels with enhanced pasting properties, gel texture, and printability, thereby expanding the potential of starch applications.

Structural modification of fiber and starch in turmeric residue by chemical and mechanical treatment for production of biodegradable films.

The dye extraction from turmeric rhizomes (Curcuma longa L.) is generated a residue with high starch content that in nature does not form film. Therefore, we decided evaluate how mechanical treatment (ball or cryogenic mill) and chemical treatment with alkali (NaOH 2.5% (1, 4, or 8 h) and bleaching with NaClO or H2O2 at 25 or 45 °C affect the chemical structure of the starch and fibers in turmeric residue, and its filmogenic capacity. Ball milling decreased the turmeric residue particle size more effectively favoring the chemical procedures. Only two types of chemical treatment consisting in alkaline treatment for 4 h and bleaching with NaClO and H2O2, respectively, for 4 h, at 25 °C yielded turmeric residues with filmogenic capacity. The chemical treatments oxidized the starch granules causing to lose their crystal structure as verified by DRX, and removed amorphous fibers such as lignin and hemicellulose increasing cellulose content in turmeric residue. FTIR analyses also revealed that the starch granules were oxidized. As bleaching agent, NaClO caused greater starch oxidation (the highest carboxyl and carbonyl groups contents) affording films with the best mechanical and functional properties. Although chemical treatment reduced the turmeric residue phenolic compounds, the films still presented antioxidant activity.

Formation of carrageenan-CaCO3 bioactive membranes.

The high biocompatibility and resorbability of polymeric membranes have encouraged their use to manufacture medical devices. Here, we report on the preparation of membranes consisting of carrageenan, a naturally occurring sulfated polysaccharide that forms helical structures in the presence of calcium ions. We incorporated CaCO3 particles into the membranes to enhance their bioactivity and mechanical properties. Infrared spectroscopy and X-ray diffraction data confirmed CaCO3 incorporation into the polymeric matrix. We tested the bioactivity of the samples by immersing them in a solution that mimics the ionic composition and pH of the human body fluid. The hybrid membranes generated hydroxyapatite, as attested by X-ray diffraction data. Scanning electron and atomic force microscopies aided investigation of membrane topography before and after CaCO3 deposition. The wettability and surface free energy, evaluated by contact angle measures, increased in the presence of CaCO3 particles. These parameters are important for membrane implantation in the body. Moreover, membrane stiffness was up to 110% higher in the presence of the inorganic particles, as revealed by Young's modulus.