Atomic force microscopy of gastric mucin and chitosan mucoadhesive systems

Deacon, Matthew P.; McGurk, Simon L.; Roberts, Clive J.; Williams, Philippa; Tendler, Saul J. B.; Davies, Martyn C.; Davis, S.S.; Harding, Stephen E.

doi:10.1042/bj3480557

Cited by 117 publications

(33 citation statements)

References 22 publications

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“…We treated mica with aminopropyltriethoxysilane, a.k.a. "APTES" [17,18], to adsorb the G-wires by direct deposition onto an electropositive surface. We found no significant orientation when imaged in air (Fig.…”

Section: Resultsmentioning

confidence: 99%

Auto-orientation of G-wire DNA on mica

Vesenka¹,

Bagg²,

Wolff³

et al. 2007

Colloids and Surfaces B: Biointerfaces

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Scanning probe microscopy was used to examine the orientation of Tet1.5 quadruplex DNA polymers, a.k.a. "G-wires", after adsorption onto freshly cleaved Phyllosilicate micas. The G-wires appear to have a preferential orientation at 60• intervals after thorough rinsing and slow drying. The angles the G-wires made with the fast scan direction of the SPM probe were measured and the frequency-angle information was quantitatively characterized by an empirical correlation coefficient. Careful measurements indicate the Tet1.5 G-wires orient along the b lattice vector of mica, the next nearest neighbor potassium vacancy. A model is proposed to explain this auto-orientation affect due to alignment of the G-wires' phosphate backbone through magnesium tether cations. Pairs of adjacent, parallel phosphate groups of the G-wires (0.95 nm apart) appear to align with the next nearest neighbor potassium vacancy sites of mica (0.90 nm apart). This behavior is not observed in solution. The potential for using the auto-orientation phenomena in the development of high-density biomolecular nano-electronic devices is explored.

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Section: Resultsmentioning

confidence: 99%

Auto-orientation of G-wire DNA on mica

Vesenka¹,

Bagg²,

Wolff³

et al. 2007

Colloids and Surfaces B: Biointerfaces

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“…Besides increasing permeability, chitosan exhibits its mucoadhesive property via interacting with negatively charged sialic acid residues on mucin at physiological pH. 15) Incorporating chitosan into micro/nanoparticles also preserves mucoadhesion, which along with the abovementioned features contribute to its widespread evaluation for oral delivery of therapeutic agents. Nguyen et al developed exendin-4-loaded nanoparticles composed of chitosan and poly(γ-glutamic acid) by using a simple ionic gelation method, and the prepared nanoparticles were then freeze-dried and filled in enteric-coated hard gelatin capsules to release nanoparticles in the proximal segment of the intestine.…”

Section: )mentioning

confidence: 99%

Permeability of Exendin-4-Loaded Chitosan Nanoparticles across MDCK Cell Monolayers and Rat Small Intestine

Wang

Zhang

Sun

et al. 2014

Biological & Pharmaceutical Bulletin

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The purpose of this study was to investigate the permeability of exendin-4-loaded chitosan nanoparticles using the Madin Darby canine kidney (MDCK) cell monolayer as an in vitro model and the rat intestine as an ex vivo model of the human intestinal barrier. A series of formulations of sodium tripolyphosphate (TPP) and chitosan with different molecular weights and degrees of deacetylation was evaluated. The formulation consisting of 0.1% TPP and 0.2% chitosan (400 kDa, 95% degree of deacetylation), which gave optimized monodispersed particle size (303.1 10.36 nm), zeta potential (18.37 1.15 mV) and encapsulation efficiency (38.0 2.6%), was used for further analysis. After determining their biocompatibility, the transport potential of drug-loaded chitosan nanoparticles was evaluated and compared with free exendin-4 using both MDCK cell monolayers and different rat intestinal segments. Mechanisms underlying enhanced transport of exendin-4 in the cell model were also explored. Compared with free exendin-4, the absorption of optimized chitosan nanoparticles was enhanced by 4.7-fold in MDCK cell monolayers and by 2.0-2.78-fold in different rat intestinal segments, with no significant difference between the duodenum, jejunum and ileum. As supported by confocal laser scanning microscopic analysis, the lower enhancement of absorption in the intestine compared to the cell monolayer likely resulted from the chitosan nanoparticle-mediated opening of cellular tight junctions and not through intracellular transport. These findings suggest that the potential application of chitosan nanoparticles as delivery carriers of exendin-4 is limited and may need further modifications.

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“…For example both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) have been used to investigate the interaction of mucin with chitosan solution (Fiebrig et al 1995) and chitosan microspheres (Genta et al 1998). Furthermore, atomic force microscopy (AFM) has been used to study aggregates of polymers and mucin (Deacon et al 2000) and polymer adsorption to cell surfaces (Patel et al 2000). NMR microscopy has been used to study the diffusion of water in the bioadhesive bond between alginate and a mucin solution (Marshall et al 2001).…”

Section: Miscellaneous Methodsmentioning

confidence: 99%

“…Films made from the positively charged chitosan had a significantly higher force of detachment than the two negatively charged polymers, polycarbophil and CMC. Deacon et al (2000) used AFM to study the interaction between chitosan and pig gastric mucin at a variety of ionic strengths, showing that electrostatic interactions are important for promoting mucoadhesive interactions at physiological ionic strength.…”

Section: Chemical Structurementioning

confidence: 99%

Pharmaceutical applications of mucoadhesion for the non-oral routes

Edsman

Hägerström

2005

Journal of Pharmacy and Pharmacology

152

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The adhesion of pharmaceutical formulations to the mucosal tissue offers the possibility of creating an intimate and prolonged contact at the site of administration. This prolonged residence time can result in enhanced absorption and, in combination with a controlled release of the drug, also improved patient compliance by reducing the frequency of administration. During the almost 30 years over which mucoadhesion has been studied, a considerable amount of knowledge has been gained, and much has been learned about the different mechanisms occurring at the formulationmucus interface and the properties that affect these mechanisms. The in-vivo performance of a dosage form not only depends on the mechanisms occurring at the interface, but also on the properties of the total mucoadhesive complex: the dosage form, the mucosa and the interface between them. A wide variety of methods are used for studying mucoadhesion; some rather similar to the in-vivo situation and some mimicking the interface alone. In this review, the mucus surface, the methods used for the study of mucoadhesion, the different mechanisms involved in mucoadhesion and theories underpinning them have been described. The complexity of mucoadhesion when trying to systemize the subject will also be discussed. The last part of the review describes the buccal, nasal, ocular, vaginal and rectal routes and provides examples of what can be achieved in-vivo when using mucoadhesive formulations.

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Atomic force microscopy of gastric mucin and chitosan mucoadhesive systems

Cited by 117 publications

References 22 publications

Auto-orientation of G-wire DNA on mica

Auto-orientation of G-wire DNA on mica

Permeability of Exendin-4-Loaded Chitosan Nanoparticles across MDCK Cell Monolayers and Rat Small Intestine

Pharmaceutical applications of mucoadhesion for the non-oral routes

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