Green composites, composed of bio-based matrices and natural fibers, are a sustainable alternative for composites based on conventional thermoplastics and glass fibers. In this work, micronized bleached Eucalyptus kraft pulp (BEKP) fibers were used as reinforcement in biopolymeric matrices, namely poly(lactic acid) (PLA) and poly(hydroxybutyrate) (PHB). The influence of the load and aspect ratio of the mechanically treated microfibers on the morphology, water uptake, melt flowability, and mechanical and thermal properties of the green composites were investigated. Increasing fiber loads raised the tensile and flexural moduli as well as the tensile strength of the composites, while decreasing their elongation at the break and melt flow rate. The reduced aspect ratio of the micronized fibers (in the range from 11.0 to 28.9) improved their embedment in the matrices, particularly for PHB, leading to superior mechanical performance and lower water uptake when compared with the composites with non-micronized pulp fibers. The overall results show that micronization is a simple and sustainable alternative for conventional chemical treatments in the manufacturing of entirely bio-based composites.
In this study, alginate nanocomposite hydrogel bioinks reinforced with lysozyme nanofibers (LNFs) were developed. Alginate-LNF (A-LNF) suspensions with different LNF contents (1, 5 and 10 wt.%) were prepared and pre-crosslinked with 0.5% (w/v) CaCl2 to formulate A-LNF inks. These inks exhibit proper shear-thinning behavior and good recovery properties (~90%), with the pre-crosslinking step playing a crucial role. A-LNF fully crosslinked hydrogels (with 2% (w/v) CaCl2) that mimic 3D printing scaffolds were prepared, and it was observed that the addition of LNFs improved several properties of the hydrogels, such as the morphology, swelling and degradation profiles, and mechanical properties. All formulations are also noncytotoxic towards HaCaT cells. The printing parameters and 3D scaffold model were then optimized, with A-LNF inks showing improved printability. Selected A-LNF inks (A-LNF0 and A-LNF5) were loaded with HaCaT cells (cell density 2 × 106 cells mL−1), and the cell viability within the bioprinted scaffolds was evaluated for 1, 3 and 7 days, with scaffolds printed with the A-LNF5 bioink showing the highest values for 7 days (87.99 ± 1.28%). Hence, A-LNF bioinks exhibited improved rheological performance, printability and biological properties representing a good strategy to overcome the main limitations of alginate-based bioinks.
The global demand for sustainable textile fibers is growing and has led to an increasing research interest from both academia and industry to find effective solutions. In this research, regenerated wood pulp fibers were functionalized with glycidyltrimethylammonium chloride (GTAC) to produce modified regenerated cellulose with cationic pending groups for improved dye uptake. The resultant cationic cellulose with a degree of substitution (DS) between 0.13 and 0.33 exhibited distinct morphologies and contact angles with water ranging from 65.7° to 82.5° for the fibers with DS values of 0.13 and 0.33, respectively. Furthermore, the thermal stability of the modified regenerated cellulose fibers, albeit lower than the pristine ones, reached temperatures up to 220 °C. Additionally, the modified fibers showed higher dye exhaustion and dye fixation values than the non-modified ones, attaining maxima values of 89.3% ± 0.9% and 80.6% ± 1.3%, respectively, for the cationic fibers with a DS of 0.13. These values of dye exhaustion and dye fixation are ca. 34% and 77% higher than those obtained for the non-modified fibers. Overall, regenerated wood pulp cellulose fibers can be used, after cationization, as textiles fiber with enhanced dye uptake performance that might offer new options for dyeing treatments.
Biopolymeric injectable
hydrogels are promising biomaterials
for
myocardial regeneration applications. Besides being biocompatible,
they adjust themselves, perfectly fitting the surrounding tissue.
However, due to their nature, biopolymeric hydrogels usually lack
desirable functionalities, such as antioxidant activity and electrical
conductivity, and in some cases, mechanical performance. Protein nanofibrils
(NFs), such as lysozyme nanofibrils (LNFs), are proteic nanostructures
with excellent mechanical performance and antioxidant activity, which
can work as nanotemplates to produce metallic nanoparticles. Here,
gold nanoparticles (AuNPs) were synthesized in situ in the presence
of LNFs, and the obtained hybrid AuNPs@LNFs were incorporated into
gelatin-hyaluronic acid (HA) hydrogels for myocardial regeneration
applications. The resulting nanocomposite hydrogels showed improved
rheological properties, mechanical resilience, antioxidant activity,
and electrical conductivity, especially for the hydrogels containing
AuNPs@LNFs. The swelling and bioresorbability ratios of these hydrogels
are favorably adjusted at lower pH levels, which correspond to the
ones in inflamed tissues. These improvements were observed while maintaining
important properties, namely, injectability, biocompatibility, and
the ability to release a model drug. Additionally, the presence of
AuNPs allowed the hydrogels to be monitorable through computer tomography.
This work demonstrates that LNFs and AuNPs@LNFs are excellent functional
nanostructures to formulate injectable biopolymeric nanocomposite
hydrogels for myocardial regeneration applications.
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