RESUMEN
The effects of cellulose nanocrystals (CNC) and microcrystalline cellulose (MCC) on the gel properties and microstructure of glucono-δ-lactone-induced soy protein isolate (SPI) gels were investigated. The water-holding capacity, gel strength, and viscoelastic modulus of CNC-SPI gels were positively associated with CNC concentration from 0 to 0.75% (w/v). In contrast, MCC-SPI gels exhibited decreased water-holding capacity, gel strength, and viscoelastic modulus. All composite gels displayed high frequency dependence and the typical type I (strain thinning) network behavior. Changes in viscoelasticity under large strain were correlated with differences in the microstructure of SPI composite gels. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) showed that CNC were more evenly and steadily distributed in the protein matrix and formed a compact network structure. In contrast, MCC-SPI gels exhibited a discontinued and rough gel network with some large aggregates and pores, in which MCC was randomly entrapped. Fourier transform infrared spectroscopy (FTIR) and molecular forces results revealed that no new chemical bonds were formed in the gelation process and that the disulfide bond was of crucial importance in the gel system. With the addition of CNC, electrostatic interactions, hydrophobic interactions, and hydrogen bonds in the SPI gel network were significantly strengthened. However, the incorporation of MCC might obstruct the connection of the protein network. It is concluded that both cellulose type and concentration affect gelling properties.
RESUMEN
In this work, the effects of calcium chloride (CaCl2) concentration on the creep-recovery, linear and nonlinear rheological behavior of nanocellulose gels had been investigated to quantify gel properties. The absolute zeta potential of nanocellulose gels were decreased as the CaCl2 concentration increased, which was related to the electrostatic repulsion that origin from carboxyl group could be effectively screened with increasing CaCl2 concentration. Rheological measurements further confirmed this result for nanocellulose gels, which revealed that the increased modulus and viscoelastic properties were obtained in the presence of CaCl2. The rheological properties of nanocellulose gels were showed to depend on CaCl2 concentration. The enhanced gel network structure was related to the Ca2+ ions that promoted crosslink between nanocellulose by salt bridge. This work highlighted the potential of using electrostatic complexation between nanocellulose and Ca2+ ions to form gels, and demonstrated the tunability of the rheological behavior by adjusting the concentration of CaCl2.
RESUMEN
Cellulose and TEMPO-oxidized cellulose fibers (TOCF) from the wheat straw were prepared with ultrasonic and chemical treatments to investigate structure and functionalities. Sol-gel transition of TOCF suspensions has been investigated using rheology to unveil the roles of ultrasonic pretreatment and temperature at various concentration. It was found that TOCF extracted with or without ultrasonic pretreatment exhibit similar functional groups in FTIR. However, different crystal structures and thermal stabilities were revealed in XRD and TGA, respectively. The gelation was independent of the ultrasonic pretreatment, while the rheological properties were highly infuenced by the concentration and temperature of the TOCF suspensions. TOCF suspensions presented a strain thinning behavior in large amplitude oscillatory shear tests. Lissajous curves showed that the elastoplastic behavior was predominantly modulated by the fiber concentration and strain amplitude other than the ultrasonic pretreatment. These results could improve the understanding of the relationships between TOCF structure and rheological properties.
RESUMEN
Polyvinylpyrrolidone (PVP) is capable of forming complexes in aqueous solutions with poorly soluble drugs, dramatically increasing their aqueous solubility and formulating stable aqueous solutions. These self-assembled complexes could potentially be explored as an ocular drug delivery system. This study assumes that these PVP medicine complexes can improve ocular permeation and strengthen the drugs' therapeutic effects. PVP K-17PF (17PF) and naringenin (NAR) could formulate into self-assembly nanocomplexes (17PF-NAR). The optimal formulation featured a 17PF/NAR weight ratio 20:1 with a complexation efficiency of 98.51 ± 0.86 percent, a mean diameter 6.73 ± 0.42 nm, and a polydispersity index 0.254 ± 0.019. This 17PF-NAR nanocomplex ophthalmic solution was stable in well storage at both 4° and 25 °C for 12 weeks. The 17PF-NAR nanocomplexes were observed to significantly improve in vitro antioxidant activity and membrane permeation of NAR. The 17PF-NAR nanocomplex ophthalmic solution had good in vitro cellular tolerance and well in vivo tolerated in rabbits. The 17PF-NAR nanocomplexes also demonstrated significant improvement in in vivo intraocular permeation of NAR and in vivo anti-inflammatory efficacy. These results indicated that nanocomplexes based on 17PF have great potential as novel nanoformulations to improve the ocular bioavailability and therapeutic efficacy of poorly water-soluble agents such as NAR.