Hydrolyzed collagen (HC) is a group of peptides with low molecular weight (3–6 KDa) that can be obtained by enzymatic action in acid or alkaline media at a specific incubation temperature. HC can be extracted from different sources such as bovine or porcine. These sources have presented health limitations in the last years. Recently research has shown good properties of the HC found in skin, scale, and bones from marine sources. Type and source of extraction are the main factors that affect HC properties, such as molecular weight of the peptide chain, solubility, and functional activity. HC is widely used in several industries including food, pharmaceutical, cosmetic, biomedical, and leather industries. The present review presents the different types of HC, sources of extraction, and their applications as a biomaterial.

Hydrolyzed Collagen-Sources and Applications.

Cellulose nanocrystals (CNCs) are bio-based, high aspect ratio nanoparticles that are industrially produced in tonne-per-day quantities across the globe. CNCs can be used to improve the performance of a large range of materials such as emulsions and foams, biomedical devices, electronics and sensors, high-viscosity fluids and polymer composites. Their ability to do so, however, is highly dependent on the way they are produced. In this Review, we assess the properties of CNCs from more than 30 production routes and 40 biomass sources to help CNC users select the right material for their desired application. CNCs produced by various methods are evaluated against three target properties: colloidal stability, size and crystallinity index. Alternative production routes and/or starting materials are suggested to overcome challenges associated with CNC use, including increasing compatibility with hydrophobic materials, resistance to thermal degradation and colloidal stability in high ionic strength environments. Additionally, we discuss industrial production of CNCs, as well as considerations for increasing the yield and reducing the environmental impact of these processes. Overall, this Review guides researchers and CNC users towards a deeper understanding of how production processes can be modified to control CNC properties and subsequently tailor their performance. Cellulose nanocrystals are rigid rod-shaped nanoparticles that show promise as additives in composites, emulsions, foams and biomedical devices and as rheological modifiers. In this Review, the authors guide end users towards selecting cellulose sources and production routes that optimize the performance of cellulose nanocrystals in their intended application.

Production routes to tailor the performance of cellulose nanocrystals

As the most abundant biopolymer on the earth, cellulose has recently gained significant attention in the development of antibacterial biomaterials. Biodegradability, renewability, strong mechanical properties, tunable aspect ratio, and low density offer tremendous possibilities for the use of cellulose in various fields. Owing to the high number of reactive groups (i.e., hydroxyl groups) on the cellulose surface, it can be readily functionalized with various functional groups, such as aldehydes, carboxylic acids, and amines, leading to diverse properties. In addition, the ease of surface modification of cellulose expands the range of compounds which can be grafted onto its structure, such as proteins, polymers, metal nanoparticles, and antibiotics. There are many studies in which cellulose nano-/microfibrils and nanocrystals are used as a support for antibacterial agents. However, little is known about the relationship between cellulose chemical surface modification and its antibacterial activity or biocompatibility. In this study, we have summarized various techniques for surface modifications of cellulose nanostructures and its derivatives along with their antibacterial and biocompatibility behavior to develop non-leaching and durable antibacterial materials. Despite the high effectiveness of surface-modified cellulosic antibacterial materials, more studies on their mechanism of action, the relationship between their properties and their effectivity, and more in vivo studies are required.

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A Review on Surface-Functionalized Cellulosic Nanostructures as Biocompatible Antibacterial Materials

New fluorescent liquid crystalline (LC) compounds containing the 2,1,3-benzothiadiazole chromophore as the central core substituted with 1,2,4-oxadiazole, 1,2,3-triazole and 1,2-isoxazole heterocycles were synthesised and their mesophases characterised by polarised optical microscopy, differential scanning calorimetry and X-ray diffraction. We observed that the bent angles of the five-membered heterocyclic substituents are crucial in determining the thermal stability of the LC phases formed, indicating a delicate balance of forces involved in LC phases. The mesophases formed by all symmetrical and unsymmetrical compounds showed thermal stability in the order 1,2-isoxazole > 1,2,3-triazole > 1,2,4-oxadiazole.

New Luminescent Liquid Crystals Based on 2,1,3-Benzothiadiazole and Bent Five-membered N-Heterocyclic Cores

New polycatenar liquid crystals containing two 1,3,4-oxadiazole rings interconnected by a bent 1,3-substituted benzene ring as the central linking unit and three alkoxy chains at each terminal have been synthesized and investigated by polarizing microscopy, DSC, XRD scattering, UV-vis spectroscopy and photoluminescence measurements All compounds form enantiotropic hexagonal columnar phases and have broader mesophase ranges than the corresponding para substituted analogues and show strong blue fluorescence emission with a large Stokes shift in solution

Columnar mesophases of luminescent polycatenar liquid crystals incorporating a 1,3-substituted benzene ring interconnecting two 1,3,4-oxadiazoles

Temperature dependence of refractive indices near uniaxial–biaxial nematic phase transition

Lyotropic nematic textures are investigated, by image processing, near the reentrant isotropic (IRE)–discotic nematic (ND)–biaxial nematic (NB)–clamitic nematic (NC)–isotropic (I) phase transitions in a lyotropic mixture of potassium laurate, decanol, and D2O. The (NB), intermediate phase between the two uniaxial nematic ones, is characterized by optical birefringence measurements and discussed in terms of structural changes in the image frame by means of an adequate statistical approach. PACS: 61.30.-v, 64.70.Md, 42.65.Jx

A.R. Sampaio

Papers

Temperature dependence of refractive indices near uniaxial–biaxial nematic phase transition

Investigation of uniaxial and biaxial lyotropic nematic phase transitions by means of digital image processing

Cellulose Nanocrystals as a Sustainable Raw Material: Cytotoxicity and Applications on Healthcare Technology

Image processing as a tool for phase transitions identification

Thermal and rheological properties of soapberry Sapindus saponaria L. (Sapindaceae) oil biodiesel and its blends with petrodiesel