Controlled drug delivery to the lung: influence of hyaluronic acid solution conformation on its adsorption to hydrophobic drug particles

J.J. Rouse, T.L. Whateley, M. Thomas, G.M. Eccleston

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

This work reports investigations into the interaction and adsorption of the hydrophilic polymer hyaluronic acid (HA) onto the surface of the hydrophobic corticosteroid drug fluticasone propionate (FP). The eventual aim is to formulate a bioadhesive pulmonary drug delivery system with prolonged action that avoids rapid clearance from the lungs by the mucociliary escalator.

Adsorption isotherms detailing the adsorption of HA from aqueous HA solution concentrations ranging from 0.14 to 0.0008% (w/v) to a fixed FP particle concentration of 0.1% (w/v) were investigated. The method of preparing FP particles with HA molecules adsorbed on their surfaces (FP/HA particles) involved suspension of the FP either in hydrated HA solution or in water followed by addition of solid HA, centrifugation of the solids to form a pellet, washing the pellet several times with water until no HA was found in the supernatant and then freeze drying the suspension obtained by dispersing the final pellet. The freeze dried powder was then analysed for adsorbed HA using a Stains-all assay. The influence of order of addition of HA to FP, time for the adsorption process, and temperature of preparation on the adsorption isotherms was investigated.

The non-equilibrium adsorption isotherms produced generally followed the same trend, in that as the HA solution concentration increased, the amount of HA adsorbed increased to a maximum at a solution concentration of ∼0.1% (w/v) and then decreased. The maxima in the adsorption isotherms were close to the change from secondary to tertiary conformation in the HA solutions. Below the maxima, adsorption occurred via interaction of FP with the hydrophobic patches along the HA chains in the secondary structures. Above the maxima, secondary HA molecules aggregate in solution to form tertiary network structures. Adsorption from tertiary structure was reduced because strong interactions between the HA molecules limited the availability of hydrophobic patches for adsorption of HA onto FP. The influence of preparation variables on adsorption was also related to the availability of hydrophobic patches for adsorption.

LanguageEnglish
Pages175-182
Number of pages8
JournalInternational Journal of Pharmaceutics
Volume330
Issue number1-2
DOIs
Publication statusPublished - 7 Feb 2007

Fingerprint

Hyaluronic Acid
Adsorption
Lung
Pharmaceutical Preparations
Suspensions
Elevators and Escalators
Mucociliary Clearance
Freeze Drying
Fluticasone
Water
Drug Delivery Systems
Centrifugation
Hydrophobic and Hydrophilic Interactions
Powders

Keywords

  • hyaluronic acid
  • fluticasone propionate
  • corticosteroid
  • adsorption isotherms
  • bioadhesive
  • pulmonary delivery

Cite this

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title = "Controlled drug delivery to the lung: influence of hyaluronic acid solution conformation on its adsorption to hydrophobic drug particles",
abstract = "This work reports investigations into the interaction and adsorption of the hydrophilic polymer hyaluronic acid (HA) onto the surface of the hydrophobic corticosteroid drug fluticasone propionate (FP). The eventual aim is to formulate a bioadhesive pulmonary drug delivery system with prolonged action that avoids rapid clearance from the lungs by the mucociliary escalator. Adsorption isotherms detailing the adsorption of HA from aqueous HA solution concentrations ranging from 0.14 to 0.0008{\%} (w/v) to a fixed FP particle concentration of 0.1{\%} (w/v) were investigated. The method of preparing FP particles with HA molecules adsorbed on their surfaces (FP/HA particles) involved suspension of the FP either in hydrated HA solution or in water followed by addition of solid HA, centrifugation of the solids to form a pellet, washing the pellet several times with water until no HA was found in the supernatant and then freeze drying the suspension obtained by dispersing the final pellet. The freeze dried powder was then analysed for adsorbed HA using a Stains-all assay. The influence of order of addition of HA to FP, time for the adsorption process, and temperature of preparation on the adsorption isotherms was investigated. The non-equilibrium adsorption isotherms produced generally followed the same trend, in that as the HA solution concentration increased, the amount of HA adsorbed increased to a maximum at a solution concentration of ∼0.1{\%} (w/v) and then decreased. The maxima in the adsorption isotherms were close to the change from secondary to tertiary conformation in the HA solutions. Below the maxima, adsorption occurred via interaction of FP with the hydrophobic patches along the HA chains in the secondary structures. Above the maxima, secondary HA molecules aggregate in solution to form tertiary network structures. Adsorption from tertiary structure was reduced because strong interactions between the HA molecules limited the availability of hydrophobic patches for adsorption of HA onto FP. The influence of preparation variables on adsorption was also related to the availability of hydrophobic patches for adsorption.",
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Controlled drug delivery to the lung : influence of hyaluronic acid solution conformation on its adsorption to hydrophobic drug particles. / Rouse, J.J.; Whateley, T.L.; Thomas, M.; Eccleston, G.M.

In: International Journal of Pharmaceutics, Vol. 330, No. 1-2, 07.02.2007, p. 175-182.

Research output: Contribution to journalArticle

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T2 - International Journal of Pharmaceutics

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KW - hyaluronic acid

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KW - corticosteroid

KW - adsorption isotherms

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