Screening for synergistic interactions in dilute polysaccharide solutions

©1995. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ This document is the Accepted, version of a Published Work that appeared in final form in Carbohydrate Polymers. To access the final edited and published work see https://doi.org/10.1016/0144-8617(95)00098-4A simple viscometric approach has been used to screen for binding interactions between different polysaccharides in very dilute solution where exclusion effects should be negligible. The method involves preparing stock solutions to approximately the same, low, viscosity (ηsp ≈ l), dialysing to identical ionic conditions, mixing in various proportions, and looking ror departures from the initial common viscosity. Mixtures of xanthan or de-acetylated xanthan with locust bean gum (LBG) or konjac glucomannan (KM) show massive enhancement of viscosity, as anticipated from the formation of synergistic gels at higher concentrations. However, no viscosity changes on mixing with LBG or KM were observed for other conformationally ordered bacterial polysaccharides (welan and rhamsan) or for alginate and pectin with sufficient Ca2+ to induce almost complete conversion to the dimeric ‘egg box’ form, demonstrating that conformational rigidity is not, in itself, sufficient for other polysaccharides to form heterotypic junctions with mannan or glucomannan chains. Interactions of carrageenans with LBG appear to depend on both conformation and the extent of aggregation. Mixtures of LBG with K+ kappa carrageenan in 100 mM KCl (which is known to promote extensive aggregation of double helices) gave erratic values for rotational viscosity and showed typical gel-like mechanical spectra under low-amplitude oscillation. Disordered carrageenans (K+ kappa in water and lambda in 100 mM KC1) showed no evidence of interaction with LBG. Negative results were also obtained for iota carrageenan under ionic conditions believed to promote ordering without significant aggregation (100 mM KCl). However, under conditions where limited aggregation might be expected (iota carrageenan in 90 mM CaC12; Me4N+ kappa carrageenan in 150 mM Me4NI), significant reductions in viscosity were observed on mixing with LBG, which may indicate some intermolecular association but without the formation of an extended network structure

Rheology of okra (Hibiscus esculentus L.) and dika nut (Irvingia gabonensis) polysaccharides

©1996. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ This document is the Accepted, version of a Published Work that appeared in final form in Carbohydrate Polymers. To access the final edited and published work see https://doi.org/10.1016/0144-8617(96)00016-1Polysaccharide extracts were prepared from two traditional food thickeners with extensive domestic use in central and western parts of Africa: okra (Hibiscus esculentis L.) and the seed kernel from 'dika nut' (lrvingia gabonensis). Both demonstrated typical polyelectrolyte behaviour in solution, and were therefore studied under fixed ionic conditions (0.1 M NaCl), yielding intrinsic viscosities of [77) = 7.6 di g1 for okra and [77) = 4.4 di g1 for dika. Concentrated solutions gave mechanical SJ?ectra typical of entangled networks, with close Cox-Merz superposition of 17 (w) and 77(y). The variation of 'zero-shear' specific viscosity with degree of space-occupancy (c[77)) was also broadly similar to the general form observed for most disordered polysaccharides, but with greater separation of c' and c'* and steeper slope of log 17sp vs. log c above c' (~4.0 for okra and ~4.6 for dika, in comparison with the usual value of ~3.3). As found for normal disordered polysaccharides, the shear-thinning behaviour of dika gum could be reduced to a single 'master-curve' for all concentrations above c'*, but the absolute value ofthe terminal slope oflog (77 - 17s) vs. logy was unusually low (~0.58, in comparison with the normal value of ~0.76). Terminal slopes for okra gum were also unusually low, and varied systematically with polymer concentration. These departures from normal solution properties are tentatively ascribed to compact macromolecular structures, coupled, in the case of okra gum, with a strong tendency to self-association

Solution rheology of mesquite gum in comparison with gum arabic

©1995. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ This document is the Accepted, version of a Published Work that appeared in final form in Carbohydrate Polymers. To access the final edited and published work see https://doi.org/10.1016/0144-8617(95)00031-2Commercial samples of mesquite gum and food-grade gum arabic were purified by filtration, alcohol precipitation, and extensive dialysis, and their rheological properties were characterised over the full range of concentrations at which solutions could be prepared (up to ~50% w/w). Both gave typical solution-like mechanical spectra, with close Cox-Merz superposition of 71(-y) and 71*(w) and only slight shear thinning at the highest accessible concentrations, and (In 71rei)/c varied linearly with log c from below 2% w/w to above 50%. The intrinsic viscosity of mesquite gum q11] � 0· 11 di g-1 ) was appreciably lower than that of gum arabic ([71] � 0-19 dig- in 0-1 M NaCl at 20°C), and was independent of ionic strength above I� 0-05, indicating a compact structure capable of only limited contraction. Departures from dilute-solution behaviour (71 ~ c1 • 4) occurred at c [71] � I for both materials, with a progressive increase in concentration dependence at higher space-occupancy, behaviour typical of soft, deformable particles, rather than of interpenetrating macromolecules. The increase in viscosity with increasing concentration was steeper for mesquite, consistent with evidence from size-exclusion chromatography and dynamic light scattering that the larger (and presumably more deformable) 'wattle blossom' component of gum arabic was absent from the mesquite gum sample

Electrostatic Self-Assembled Chitosan-Pectin Nano- and Microparticles for Insulin Delivery

A polyelectrolyte complex system of chitosan-pectin nano- and microparticles was developed to encapsulate the hormone insulin. The aim of this work was to obtain small particles for oral insulin delivery without chemical crosslinkers based on natural and biodegradable polysaccharides. The nano- and microparticles were developed using chitosans (with different degrees of acetylation: 15.0% and 28.8%) and pectin solutions at various charge ratios (n+/n− given by the chitosan/pectin mass ratio) and total charge. Nano- and microparticles were characterized regarding particle size, zeta potential, production yield, encapsulation efficiency, stability in different media, transmission electron microscopy and cytotoxicity assays using Caco-2 cells. The insulin release was evaluated in vitro in simulated gastric and intestinal media. Small-sized particles (~240–~1900 nm) with a maximum production yield of ~34.0% were obtained. The highest encapsulation efficiency (~62.0%) of the system was observed at a charge ratio (n+/n−) 5.00. The system was stable in various media, particularly in simulated gastric fluid (pH 1.2). Transmission electron microscopy (TEM) analysis showed spherical shape particles when insulin was added to the system. In simulated intestinal fluid (pH 6.8), controlled insulin release occurred over 2 h. In vitro tests indicated that the proposed system presents potential as a drug delivery for oral administration of bioactive peptide

Immunological and functional properties of the exudate gum from northwestern Mexican mesquite (Prosopis spp.) in comparison with gum arabic

©1997. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ This document is the Accepted, version of a Published Work that appeared in final form in International Journal of Biological Macromolecules. To access the final edited and published work see https://doi.org/10.1016/S0141-8130(97)00037-8A comparison between the fine structural features of exudate gum from mesquite (Prosopis spp.) indigenous to NW Mexico and commercial gum arabic from Acacia spp. was achieved by means of immunological techniques. Their functional properties were compared from the ability to form oil-in-water emulsions and encapsulate cold press orange peel essential oil by spray drying. Fine comparison of the antigenic compounds in both materials against polyclonal rabbit antibodies, showed that the carbohydrate-rich components with slow mobility of mesquite gum are closely related to the faster ones of gum arabic. Also, close identity was observed for the components in the proteic fraction of both gums. Similar tannin concentrations were found in both materials (:0.43%) with only dark coloured samples bearing higher amounts (:1.9%). Gum arabic retained nearly 100% of the quantity of orange peel essential oil emulsified in water before spray drying, while mesquite gum did so for 90.6% of the citrus oil. From these results it is believed that mesquite gum might be a suitable replacement of gum arabic in arid regions of the world were Prosopis trees have widespread occurrence

Rheological study of the chitosan/glutaraldehyde chemical gel system

©1998. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ This document is the Accepted, version of a Published Work that appeared in final form in Polymer Gels and Networks . To access the final edited and published work see https://doi.org/10.1016/S0966-7822(98)00032-XChitosan dissolved in 0.1 mol l~1 acetic acid shows an apparent yield stress at very low frequencies, probably due to a structuring process yielding gel-like response. It re#ects complex relaxation mechanisms once chains disentangle and relax, presumably due to incipient hydrophobic contacts reinforced by the relative sti!ness of the chitosan chains, which tend to slow down reptation. When chemical cross-linkages are introduced, the weak self-associated network of chitosan is gradually replaced by a permanent covalent network as the molar ratio of aldehyde/amine groups, R, is increased. At R"0.4 a glass-to-rubber-type transition is observed, while at R"0.5 the form of the mechanical spectrum suggests the co-existence of a chemically cross-linked gel &dissolved' in a second entangled network formed by chitosan chains of restricted mobility. At higher cross-linking levels (R'1) a strong permanent gel is formed. The observed frequency dependence near the rheological gel point suggests several modes of relaxation processes

A chitosan-based liposome formulation enhances the in vitro wound healing efficacy of substance P neuropeptide

Currently, there is considerable interest in developing innovative biodegradable nanoformulations for controlled administration of therapeutic proteins and peptides. Substance P (SP) is a neuropeptide of 11 amino acids that belongs to the tachykinins family and it plays an important role in wound healing. However, SP is easily degradable in vivo and has a very short half-life, so the use of chitosan-based nanocarriers could enhance its pharmaceutical properties. In light of the above, the aim of this work was to produce and characterize chitosan-coated liposomes loaded with SP (SP-CH-LP) as novel biomaterials with potential application in mucosal wound healing. The loaded system’s biophysical properties were characterized by dynamic light scattering with non-invasive back scattering (DLS-NIBS), mixed mode measurements and phase analysis light scattering (M3-PALS) and high performance liquid chromatography with ultraviolet/visible light detection (HPLC-UV/VIS). Then, the efficacy of the obtained nanoformulations was examined via proof-of-principle experiments using in vitro cell assays. These assays showed an increment on cell motility and proliferation after treatment with free and encapsulated neuropeptides. Additionally, the effect of SP on wound healing was enhanced by the entrapment on CH-LP. Overall, the amenability of chitosan-based nanomaterials to encapsulate peptides and proteins constitutes a promising approach towards potential novel therapies to treat difficult wounds

Protein delivery based on uncoated and chitosan-coated mesoporous silicon microparticles

Mesoporous silicon is a biocompatible, biodegradable material that is receiving increased attention for pharmaceutical applications due to its extensive specific surface. This feature enables to load a variety of drugs in mesoporous silicon devices by simple adsorption-based procedures. In this work, we have addressed the fabrication and characterization of two new mesoporous silicon devices prepared by electrochemistry and intended for protein delivery, namely: (i) mesoporous silicon microparticles and (ii) chitosan-coated mesoporous silicon microparticles. Both carriers were investigated for their capacity to load a therapeutic protein (insulin) and a model antigen (bovine serum albumin) by adsorption. Our results show that mesoporous silicon microparticles prepared by electrochemical methods present moderate affinity for insulin and high affinity for albumin. However, mesoporous silicon presents an extensive capacity to load both proteins, leading to systems were protein could represent the major mass fraction of the formulation. The possibility to form a chitosan coating on the microparticles surface was confirmed both qualitatively by atomic force microscopy and quantitatively by a colorimetric method. Mesoporous silicon microparticles with mean pore size of 35 nm released the loaded insulin quickly, but not instantaneously. This profile could be slowed to a certain extent by the chitosan coating modification. With their high protein loading, their capacity to provide a controlled release of insulin over a period of 60-90 min, and the potential mucoadhesive effect of the chitosan coating, these composite devices comprise several features that render them interesting candidates as transmucosal protein delivery systems

Chitosan-Grafted Copolymers and Chitosan-Ligand Conjugates as Matrices for Pulmonary Drug Delivery

Recently, much attention has been given to pulmonary drug delivery by means of nanosized systems to treat both local and systemic diseases. Among the differentmaterials used for the production of nanocarriers, chitosan enjoys high popularity due to its inherent characteristics such as biocompatibility, biodegradability, and mucoadhesion, among others. Through the modification of chitosan chemical structure, either by the addition of new chemical groups or by the functionalization with ligands, it is possible to obtain derivatives with advantageous and specific characteristics for pulmonary administration. In this paper, we discuss the advantages of using chitosan for nanotechnology-based pulmonary delivery of drugs and summarize the most recent and promising modifications performed to the chitosan molecule in order to improve its characteristics.Fil: Andrade, Fernanda. Universidad de Porto; PortugalFil: Goycoolea, Francisco. Westfalische Wilhelms Universitat; AlemaniaFil: Chiappetta, Diego Andrés. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Tecnología Farmacéutica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; ArgentinaFil: Das Neves, José. Universidad de Porto; PortugalFil: Sosnik, Alejandro Dario. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Tecnología Farmacéutica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay; ArgentinaFil: Sarmento, Bruno. Universidad de Porto; Portugal. Instituto Superior de Ciências da Saúde-Norte; Portuga