Aggregation of hydrophobically modified polysaccharides in solution and at the air–water interface

Acid-induced conformation regulation of peanut polysaccharide and its effect on stability and digestibility of oil-in-water emulsion

BACKGROUND

Developing the stable and healthy emulsion-based food is in accord with the needs of people for health. In the present study, acidification at pH 3.0 of peanut polysaccharide (APPSI) was employed to regulate its conformation and further improve its advantages in preparing oil-in-water emulsion.

RESULTS

The results indicated that acidification induced conversion of PPSI aggregates into linear chains. Increasing concentration promoted formation of cross-linked network structure shown in transmission electron microscopy images. Consequently, the viscosity, yield stress, storage modulus and flow activation energy significantly increased, further fabricating gel structure. Moreover, aggregation behavior suggested that more exposed proteins were involved in gel structure, thereby forming many hydrophobic cores as verified by fluorescence spectroscopy of pyrene. Afterwards, emulsion characteristics indicated that APPSI produced strong and thick steric hindrance around oil droplets and the coil-like interweaved chains locked the continuous phase, bringing strong elasticity and resistance to stress and creaming. Meanwhile, the lower fatty acid in APPSI-emulsion was released after simulated gastrointestinal digestion, mainly as a result of the high retention ratio of emulsion droplets. Furthermore, the elastic and viscous Lissajous curves suggested that the structure strength of APPSI-emulsion was similar to that of the salad dressing within the strain 53.22%.

CONCLUSION

The conformation of PPSI after acidification at pH 3.0 was suitable for preparing the stable emulsion. The obtained emulsion could resist digestion and maintain a strong structure, comprising a cholesterol-free and low-fat salad dressing substitute. © 2023 Society of Chemical Industry.

Characterization of hydrophobic interaction of galactomannan in aqueous solutions using fluorescence-based technique

Fluorescence probing was used to study hydrophobic interactions of galactomannan (GM) obtained from fenugreek gum (FG), guar gum (GG), and locust bean gum (LBG) at different M/G ratios. The I₁/I₃ ratio of pyrene changed from 1.73 to 1.29, 1.22, and 1.29 for FG, GG and LBG, respectively, as the concentration of GM increased from 0.01 to 8.0 g/L at 30 °C. The critical aggregation concentration of FG, GG, and LBG increased from 1.04 to 3.84 g/L, 1.15 to 3.73 g/L, and 0.94 to 3.63 g/L, respectively, as temperature increased from 10 to 70 °C. Addition of Na₂SO₄ and NaSCN increased the I₁/I₃ ratio in dilute solution, but reduced it in semi-dilute solution, whereas adding urea reduced I₁/I₃ in dilute solution but increased it in semi-dilute solution. These results indicated that the CAC of GM, polarity and number of hydrophobic microdomains were highly dependent on the M/G ratio and galactose distribution.

A simple strategy for selective photocatalysis degradation of organic dyes through selective adsorption enrichment by using a complex film of CdS and carboxylmethyl starch

Resource utilization of wastes through effective separation is a major challenge in the field of water and wastewater treatment. Photocatalytic degradation is a powerful water treatment technology but has no selectivity in degradation of various coexisting contaminants due to its strong oxidation. In this work, a complex film composed of CdS and carboxylmethyl starch (CdS/CMS) was designed and fabricated using in situ formation method. The morphology, composition, and optical property of this film were investigated in detail by various characterization methods. CdS was well distributed in the starch matrix, and the absorption wavelength of this film was still located in the visible light region. This starch-based complex film was used to remove various organic dyes [methylene blue (MB), crystal violet (CV), and rhodamine B (RhB)] from aqueous solutions by two consecutive processes of adsorption enrichment and photocatalysis degradation. 0.1 g of CdS/CMS film can remove approximately 86.72% of MB and 81.03% of CV in 120 min. CdS/CMS still exhibited evidently selective photocatalysis degradation of MB and CV in MB/RhB and CV/RhB binary systems, respectively, and had nearly no effect on RhB. The cationic groups on MB and CV can effectively interact with negatively carboxyl groups of CMS via electrostatic interactions, causing their good affinities; but the anionic groups on RhB had an electrostatic repulsion to the starch matrix. The considerably different affinities of various dyes to CMS triggered strong adsorption preferences and great selective degradation effectiveness. The selectivity of CdS/CMS could not be influenced by pH and some coexisting inorganic anions. Furthermore, this complex film did not require regeneration and could be reused directly with low removal capacity loss. Therefore, a new and simple strategy was provided to realize the effective separation and recovery of target contaminants in water by photocatalytic degradation technology.

Falkenbergia rufolanosa polysaccharide - Poly(vinyl alcohol) composite films: A promising wound healing agent against dermal laser burns in rats

This work was conducted to evaluate the compatibility between physicochemical, antioxidant and morphological properties of polysaccharide (FRP) extracted from red marine alga Falkenbergia rufolanosa reinforced by poly (vinyl alcohol) (PVA) composed films at different ratios of FRP/PVA: F1 (70:30), F2 (50:50), F3 (30:70) and PVA (100% PVA) and the potential wound healing effects. As assessed, FRP/PVA prepared films were heterogeneous, slightly opaque with a rough surface as ascertained by Fourier transform infrared spectroscopy, scanning electron microscopy and colorimetric parameters. Even, X-ray diffraction and glass transition results revealed a semi-crystalline structure of FRP composed films which decreased with increasing PVA ratios. The antioxidant activities of composite films depicted that F1 exhibited the highest antioxidant activity in vitro. Therefore, F1 was found to promote significantly the wound healing, after eight days of treatment, evidenced by higher wound appearance scores and a higher content of collagen (885.12 ± 20.35 mg/g of tissue) confirmed by histological examination, when compared with control, CYTOL BASIC® and PVA-treated groups. All together, the marine-derived polysaccharide gave a substantial pledge for the development of biodegradable films as a potent antioxidant material and a promising agent for tissue regeneration.

Microfluidics-assisted generation of stimuli-responsive hydrogels based on alginates incorporated with thermo-responsive and amphiphilic polymers as novel biomaterials

We used a droplet-based microfluidics technique to produce monodisperse responsive alginate-block-polyetheramine copolymer microgels. The polyetheramine group (PEA), corresponding to a propylene oxide /ethylene oxide ratio (PO/EO) of 29/6 (Jeffamine(®) M2005), was condensed, via the amine link, to alginates with various mannuronic/guluronic acids ratios and using two alginate:jeffamine mass ratios. The size of the grafted-alginate microgels varied from 60 to 80 μm depending on the type of alginate used and the degree of substitution. The droplet-based microfluidics technique offered exquisite control of both the dimension and physical chemical properties of the grafted-alginate microgels. These microgels were therefore comparable to isolated grafted-alginate chains in retaining both their amphiphilic and thermo-sensitive properties. Amphiphilicity was demonstrated at the oil-water interface where grafted-alginate microgels were found to decrease interfacial tension by ∼ 50%. The thermo-sensitivity of microgels was clearly demonstrated and a 10 to 20% reduction in size between was evidenced on increasing the temperature above the lower critical solution temperature (TLCST) of Jeffamine. In addition, the reversibility of thermo-sensitivity was demonstrated by studying the oil-water affinity of microgels with temperature after Congo red labeling. Finally, droplet-based microfluidics was found to be a good and promising tool for generating responsive biobased hydrogels for drug delivery applications and potential new colloidal stabilizers for dispersed systems such as Pickering emulsions.

pH-sensitive pullulan-based nanoparticle carrier of methotrexate and combretastatin A4 for the combination therapy against hepatocellular carcinoma

This study designs a pH-sensitive nanoparticle carrier of methotrexate (MTX) and combretastatin A4 (CA4) based on pullulan for the combination therapy against hepatocellular carcinoma (HCC). Briefly, N-urocanyl pullulan (URPA) with the degree of substitution (DS) of 5.2% was synthesized and then conjugated with MTX to form MTX-URPA, in which MTX content was 17.8%. MTX-URPA nanoparticles prepared by the dialysis method had spherical shape and the mean size of 187.1 nm, and showed high affinity for HepG2 cells. CA4 was successfully loaded into MTX-URPA nanoparticles and exhibited pH-sensitive in vitro release property. After intravenous injection to PLC/PRF/5-bearing nude mice, CA4 loaded MTX-URPA (CA4/MTX-URPA) nanoparticles achieved the enhanced antitumor and anti-angiogenic effects, the prolonged circulation time in blood, and the increased distributions both in the liver and the tumor. In conclusion, this drug carrier system has significant liver-targeting property and exhibits advantages for the combination therapy against hepatocellular carcinoma.

Proteins, polysaccharides, and their complexes used as stabilizers for emulsions: alternatives to synthetic surfactants in the pharmaceutical field?

Emulsions are widely used in pharmaceutics for the encapsulation, solubilization, entrapment, and controlled delivery of active ingredients. In order to answer the increasing demand for clean label excipients, natural polymers can replace the potentially irritative synthetic surfactants used in emulsion formulation. Indeed, biopolymers are currently used in the food industry to stabilize emulsions, and they appear as promising candidates in the pharmaceutical field too. All proteins and some polysaccharides are able to adsorb at a globule surface, thus decreasing the interfacial tension and enhancing the interfacial elasticity. However, most polysaccharides stabilize emulsions simply by increasing the viscosity of the continuous phase. Proteins and polysaccharides may also be associated either through covalent bonding or electrostatic interactions. The combination of the properties of these biopolymers under appropriate conditions leads to increased emulsion stability. Alternative layers of oppositely charged biopolymers can also be formed around the globules to obtain multi-layered "membranes". These layers can provide electrostatic and steric stabilization thus improving thermal stability and resistance to external treatment. The novel biopolymer-stabilized emulsions have a great potential in the pharmaceutical field for encapsulation, controlled digestion, and targeted release although several challenging issues such as storage and bacteriological concerns still need to be addressed.

Interaction of self-assembled squalenoyl gemcitabine nanoparticles with phospholipid-cholesterol monolayers mimicking a biomembrane

Gemcitabine (dFdC or Gem) is a water-soluble cytotoxic drug, with poor cellular uptake in the absence of a nucleoside transporter. To improve its diffusion through membranes, it was modified by grafting of a squalenoyl moiety. In water, this derivative is able to form stable and monodispersed nanoparticles made of inverse hexagonal phases. The formation and interfacial properties of the squalenoyl gemcitabine (SQ-Gem) nanoparticles, and their ability to interact with phospholipid and cholesterol monolayers modeling a biomembrane, was assessed from surface tension measurements and Brewster angle microscopy. To get a better insight into the mechanisms of SQ-Gem interaction with the various lipids, the interfacial behavior of SQ-Gem and squalene was also studied by surface pressure and surface potential measurements, in the absence and in the presence of phospholipids and cholesterol. The results showed that SQ-Gem nanoparticles adsorbed at the free air/water interface and disrupted to form a monolayer. SQ-Gem molecules released from the adsorbed nanoparticles were also able to penetrate into condensed phospholipid-cholesterol mixed monolayers. The kinetics of this penetration was apparently controlled by intermolecular interactions between the drug and the adsorbed lipids. Whereas distearoylphosphatidylcholine (DSPC) hindered SQ-Gem penetration, cholesterol favored it, which could have important implications in the therapeutic field since cholesterol targeting could alter lipid raft composition and cancer cell survival.

Tubular cationized pullulan hydrogels as local reservoirs for plasmid DNA

In the present study, we measured the ability of various cationized pullulan tubular hydrogels to retain plasmid DNA, and tested the ability of retained plasmid DNA to transfect vascular smooth muscle cells (VSMCs). Cationized pullulans were obtained by grafting at different charge densities ethylamine (EA) or diethylaminoethylamine (DEAE) on the pullulan backbone. Polymers were characterized by elemental analysis, acid-base titration, size exclusion chromatography, Fourier-transform infrared spectroscopy, and proton nuclear magnetic resonance. The complexation of cationized pullulans in solution with plasmid DNA was evidenced by fluorescence quenching with PicoGreen. Cationized pullulans were then chemically crosslinked with phosphorus oxychloride to obtain tubular cationized pullulan hydrogels. Native pullulan tubes did not retain loaded plasmid DNA. In contrast, the ability of cationized pullulan tubes to retain plasmid DNA was dependent on both the amine content and the type of amine. The functional integrity of plasmid DNA in cationized pullulan tubes was demonstrated by in vitro transfection of VSMCs. Hence, cationized pullulan hydrogels can be designed as tubular structures with high affinity for plasmid DNA, which may provide new biomaterials to enhance the efficiency of local arterial gene transfer strategies.

Enhancement of the Solubility and Efficacy of Poorly Water-Soluble Drugs by Hydrophobically-Modified Polysaccharide Derivatives

PURPOSE

This work was intended to develop and evaluate a new polymeric system based on amphiphilic carboxymethylpullulans (CMP(49)C(8) and CMP(12)C(8)) that can spontaneously self-assemble in aqueous solutions and efficiently solubilize hydrophobic drugs.

METHODS

The self-assembling properties of CMP(49)C(8) and CMP(12)C(8) were characterized by fluorescence spectroscopy and surface tension measurements. The solubilization of benzophenone and docetaxel was assessed from surface tension measurements, UV spectrometry and HPLC assays. The in vitro cytoxicity of CMP(49)C(8) solutions and the docetaxel commercial vehicle (Tween 80/Ethanol-water) were evaluated in the absence and in the presence of docetaxel.

RESULTS

Compared to CMP(12)C(8), CMP(49)C(8) in aqueous solutions appeared to self-organize into monomolecular aggregates containing hydrophobic nanodomains, and to significantly increase the apparent solubility of benzophenone. Docetaxel solubility could also be improved in the presence of CMP(49)C(8) but to a lower extent due to the surface properties of the drug. Nevertheless, in vitro, the cytotoxicity studies revealed that against cancer cells, the CMP(49)C(8)-docetaxel formulation was equipotent to the commercial docetaxel one. Furthermore, in the absence of the drug, CMP(49)C(8) appeared less cytotoxic against macrophages than the Tween 80/Ethanol-water.

CONCLUSIONS

CMP(49)C(8) is a good candidate for solubilizing hydrophobic drugs and could be applied to docetaxel formulations.

Spontaneous association of hydrophobized dextran and poly-β-cyclodextrin into nanoassemblies

New nanoassemblies were instantaneously prepared by mixing two aqueous solutions, one containing a beta-cyclodextrin polymer (pbetaCD), and the other a hydrophobically modified by alkyl chains dextran (MD). The formation mechanism and the inner structure of these nanoassemblies were analysed using surface tension measurements and (1)H NMR spectroscopy. The effect of a hydrophobic guest molecule, such as benzophenone (BZ), on the formation and stability of the nanoassemblies was also evaluated. MD exhibited the typical behaviour of a soluble amphiphilic molecule and adsorbed at the air/water interface. Whereas the injection of native beta-CDs in the solution beneath the adsorbed MD monolayer did not produce any change in the surface tension, that of the pbetaCD resulted in an increase in the surface tension, indicating the desorption of the polymer from the interface. This result accounts for a cooperative effect of beta-CDs linked together in the pbetaCD polymer on dextran desorption. The presence of benzophenone in the system hindered the sequestration of dextran alkyl moieties by beta-CD in the polymer without impeding the formation of associative nanoassemblies of 100-200 nm. (1)H NMR investigations demonstrated that, in the BZ-loaded nanoassemblies, the hydrophobic molecule was mainly located into the cyclodextrin cavities.