Modulating insulin-release profile from pH/thermosensitive polymeric beads through polymer molecular weight

Ramkissoon-Ganorkar, Chaaya; Liu, Feng; Baudyš, Miroslav; Kim, Sung Wan

doi:10.1016/s0168-3659(99)00006-1

Cited by 247 publications

(128 citation statements)

References 31 publications

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“…LCST Generally, the LCST value of the hydrogels is determined by the CP method at low polymer concentration (0.5-1%) [10,11], this value is then assumed to correspond to that of the hydrogels. However, the chemically cross-linked hydrogels are prepared from highly concentrated polymer solution (5-10%) [11,12].…”

Section: Influence Of the Polymer Concentration Onmentioning

confidence: 99%

“…For determining the LCST of linear thermoresponsive polymer, the cloud point (CP) method is used to determine the CP value [8], and the differential scanning calorimetry analysis applies to obtain the endothermic transition peak [9]. Usually, the concentration of the polymer solution used for the determination of the LCST value by calorimetric and absorbance studies is low (0.5-1%, w/v) [10,11]. The LCST value determined at low concentration is then taken as the VPTT of the hydrogel, although the physical and chemical crosslinked hydrogels used in biomedical applications are prepared starting from high concentrated polymer solutions (5-10%, w/v) [11,12].…”

Section: Introductionmentioning

confidence: 99%

“…Usually, the concentration of the polymer solution used for the determination of the LCST value by calorimetric and absorbance studies is low (0.5-1%, w/v) [10,11]. The LCST value determined at low concentration is then taken as the VPTT of the hydrogel, although the physical and chemical crosslinked hydrogels used in biomedical applications are prepared starting from high concentrated polymer solutions (5-10%, w/v) [11,12]. Moreover, cross-linked hydrogels in the swollen state could be considered as a concentrated polymer solution related to the amount of water retained by the hydrogel.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Lower critical solution temperature versus volume phase transition temperature in thermoresponsive drug delivery systems

Constantin¹,

Cristea²,

Ascenzi³

et al. 2011

Express Polym. Lett.

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Abstract. One of the most subtle problem in the characterization of thermoresponsive polymers is the evaluation of the relationship between the lower critical solution temperature (LCST) of the linear polymer and the volume phase transition temperature (VPTT) of the corresponding hydrogel. Here, the LCST and the onset temperature of linear poly(N-isopropylacrylamide-co-N-hydroxymethyl acrylamide) has been determined under pseudo-physiological conditions by cloud point (CP) measurements and by microcalorimetric analysis. The LCSTs, as well as the onset temperatures, determined by the CP method, decrease with increasing the concentration of the polymer solution. On the contrary, microcalorimetric analyses give almost the same values for LCSTs and the onset temperatures regardless of polymer concentration. The VPTT of the hydrogel, determined by the blue dextran method, was found to be closely similar to the LCST of the concentrated polymer solution (10%, w/v), determined by the CP method. In fact, the hydrogel could be considered as a concentrated polymer solution whose concentration could be related to the amount of water retained by the hydrogel. Hydrogel microspheres have been also reported to release diclofenac, a drug model system, in a pulsating way at temperatures slightly below and above the VPTT.

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Section: Influence Of the Polymer Concentration Onmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Lower critical solution temperature versus volume phase transition temperature in thermoresponsive drug delivery systems

Constantin¹,

Cristea²,

Ascenzi³

et al. 2011

Express Polym. Lett.

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“…INS was also labeled with fluorescein (FITC-INS) (Ramkissoon-Ganorkar et al, 1999), then FITC-INS (1 mg/ ml) with or without surfactin (1 mg/ml) was treated with pepsin at pH 1.2 as described above. After digestion, the residual precipitated particles were examined by a confocal laser scanning microscopy (CLSM) (Carl Zeiss 510-META, Oberkochen, Germany).…”

Section: Analysis Of Surfactin To Protect Ins From Pepsin and Trypsinmentioning

confidence: 99%

“…For in vivo assay, FITC-labeled surfactin (FITC-surfactin) and NHS-Rhodamine B labeled INS were synthesized and purified in the laboratory (Ramkissoon-Ganorkar et al, 1999). Prior to oral administration, diabetic mice fasted for 12 h and then orally given with 200 mg NHS-Rhodamine B-INS plus 200 mg FITC-surfactin or 200 mg NHS-Rhodamine B-INS alone.…”

Section: Determination Of Ins Absorbed By Intestine Ex Vivo and In Vivomentioning

confidence: 99%

A natural lipopeptide of surfactin for oral delivery of insulin

et al. 2016

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Surfactin, a natural lipopeptide produced by Bacillus, is gaining attention for potentially biomedical and pharmaceutical applications. Here, surfactin was assayed for oral delivery of insulin (INS) by its ability to bind to and promote protein to penetrate through the cell membrane. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, surfactin was found to form co-precipitates with INS to protect it from acidic and enzymatic attack in the gastrointestinal tract. Further analysis by non-reductive electrophoresis showed surfactin could bind to INS forming heteropolymers. Analysis with circular dichroism, we found this binding significantly influenced the INS structure with decreased rigid a-helix and b-turn, but with increased flexible b-sheet and random coil. The change with more flexible structure was favorable for INS to penetrate through the cell membrane. Fluorescence spectra analysis also showed surfactin could lead Phe and Tyr in the inner of INS exposed outside, further promoting INS permeabilization by improving the hydrophobic-lipophilic interactions between INS and cell membrane. As a result, the effective permeability (Peff) of INS plus surfactin was 4.3 times of that of INS alone. In vivo assay showed oral INS with surfactin displayed excellent hypoglycemic effects with a relative bioavailability of 12.48% and 5.97% in diabetic mice and non-diabetic dogs, respectively. Summary, surfactin is potential for oral delivery of INS by its role as an effective protease inhibitor and permeability enhancer.

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Smart Materials

Benee

Snowden

Chowdhry

2002

Encyclopedia of Polymer Science and Technology

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The nature and properties of “smart” colloidal microgels are reviewed. Detailed descriptions including mechanistic information are reported with respect to the preparation of a number of physically different microgel structures including homopolymers, copolymers, polyelectrolyte, and core–shell type materials. The principal techniques used for the characterization of microgels are described, including dynamic light scattering and differential scanning calorimetery. Microgel properties are reviewed with respect to temperature sensitivity, pH sensitivity, colloid stability, rheological behavior, osmotic deswelling, and the influence of copolymers on microgels. Applications of these types of materials are also discussed and, include drug delivery devices, binding/adsorption agents, and catalytic compounds.

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Modulating insulin-release profile from pH/thermosensitive polymeric beads through polymer molecular weight

Cited by 247 publications

References 31 publications

Lower critical solution temperature versus volume phase transition temperature in thermoresponsive drug delivery systems

Lower critical solution temperature versus volume phase transition temperature in thermoresponsive drug delivery systems

A natural lipopeptide of surfactin for oral delivery of insulin

Smart Materials

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