Collagen/Cellulose Nanofiber Blend Scaffolds Prepared at Various pH Conditions

Tunable mechanical behavior of collagen-based films: A comparison of celluloses in different geometries

Collagen (Col) films were reinforced by celluloses in different geometries: microcrystalline cellulose (MCC), cellulosic fines (CF), cellulose nanofiber (CNF) and cellulose nanocrystals (CNC). The reinforcement mechanisms were investigated by the elastoplasticity and fracture appearance. Compared with the fracture stress of collagen film (67.5 MPa), the Col-CNF films effectively borne the stress (95.8 MPa) by intercrystalline fracture, ascribing the abundant hydrogen bonding and mechanical locking between cellulose and collagen. The toughness of Col-CF films was increased by the interfibrillar slippage of CF and pull-off of CF within the matrix, improving the strain-to-break from 8.37% to 12.13%. The films added with MCC and CNC weaken the mechanical behavior, due to the defects and lack of mechanical locking. Besides, the effects of celluloses' geometries on the thickness, density, water-tightness, thermal stability, crystallinity and FTIR of films were also investigated. These provide the evidence that the geometries of fillers diversely improve the behaviors of collagen film offering strategies for the film with adjustable mechanical properties.

Detection of Human Neutrophil Elastase by Fluorescent Peptide Sensors Conjugated to TEMPO-Oxidized Nanofibrillated Cellulose

Peptide-cellulose conjugates designed for use as optical protease sensors have gained interest for point-of-care (POC) detection. Elevated serine protease levels are often found in patients with chronic illnesses, necessitating optimal biosensor design for POC assessment. Nanocellulose provides a platform for protease sensors as a transducer surface, and the employment of nanocellulose in this capacity combines its biocompatibility and high specific surface area properties to confer sensitive detection of dilute biomarkers. However, a basic understanding of the spatiotemporal relationships of the transducer surface and sensor disposition is needed to improve protease sensor design and development. Here, we examine a tripeptide, fluorogenic elastase biosensor attached to TEMPO-oxidized nanofibrillated cellulose via a polyethylene glycol linker. The synthetic conjugate was found to be active in the presence of human neutrophil elastase at levels comparable to other cellulose-based biosensors. Computational models examined the relationship of the sensor molecule to the transducer surface. The results illustrate differences in two crystallite transducer surfaces ((110) vs. (1-10)) and reveal preferred orientations of the sensor. Finally, a determination of the relative (110) vs. (1-10) orientations of crystals extracted from cotton demonstrates a preference for the (1-10) conformer. This model study potentiates the HNE sensor results for enhanced sensor activity design.

Engineering fiber anisotropy within natural collagen hydrogels

It is well known that biophysical properties of the extracellular matrix (ECM), including stiffness, porosity, composition, and fiber alignment (anisotropy), play a crucial role in controlling cell behavior in vivo. Type I collagen (collagen I) is a ubiquitous structural component in the ECM and has become a popular hydrogel material that can be tuned to replicate the mechanical properties found in vivo. In this review article, we describe popular methods to create 2-D and 3-D collagen I hydrogels with anisotropic fiber architectures. We focus on methods that can be readily translated from engineering and materials science laboratories to the life-science community with the overall goal of helping to increase the physiological relevance of cell culture assays.

Interfacial Structure Control and Three-Dimensional X-ray Imaging of an Epoxy Monolith Bonding System with Surface Modification

A monolith bonding system has a high reliability for dissimilar material bonding. The epoxy monolith layer fabricated on a substrate guarantees bond strength by the anchor effect, regardless of the compatibility of the used materials. Designing a high-performance monolith bonding system requires the suppression of an interfacial failure between the monolith and the substrate. In this study, silane and phosphine coupling agents containing amino and epoxy groups were used to construct a robust interfacial structure between the monolith and the substrates such as glass and metals. The internal and interfacial monolith structures were characterized by three-dimensional X-ray imaging as a nondestructive observation method in addition to the scanning electron microscopy of the sample cross sections. The modification of the substrate-monolith interface using the coupling agents improved the strength of dissimilar material bonding of the glass and metal substrates in combination with thermoplastic resins such as poly(ethylene terephthalate) and polycarbonate bisphenol-A.

Preparation and characterization of cellulose nanofiber cryogels as oil absorbents and enzymatic lipolysis scaffolds

Cellulose nanofiber (CNF) materials have received much attention as sustainable "green" materials with high mechanical properties. Their application in oil absorption and enzymatic lipolysis makes them further attractive from the perspective of environmental issues including marine pollution preservation. Herein, we prepared CNF cryogels with various surface properties, evaluated their capacities as oil absorbents and applied them as lipase-lipolysis scaffolds. Their obtained cryogels consisted of various modified CNFs and their structure and properties were investigated. Moreover, lipase-supported CNF cryogels were prepared for enzymatic lipolysis. The cryogels of protonated TEMPO-oxidized CNF showed the highest absorption capacity for olive oil, while all the CNF cryogels possessed similar absorption abilities towards water. In enzymatic lipolysis with lipase, the TEMPO-oxidized CNF (TOCN-Na⁺) cryogel showed the highest specific activity. The specific activities of lipase in TOCN-Na⁺ cryogels remained unchanged after being stored at 40 °C for 3 days.