title: Investigation of wetting behavior of nonaqueous ethylcellulose gel matrices using dynamic contact angle.
abstract: OBJECTIVE
  This study reports the development of a method based on dynamic contact angle to investigate the wetting behavior of non-aqueous ethylcellulose (EC) gel matrices intended for topical drug delivery.
  
  
  METHODS
  Non-aqueous gel matrices were prepared from the three fine particle grades of EC and propylene glycol dicaprylate/dicaprate. Dynamic contact angle measurements of sessile drops of water and isopropylmyristate (IPM) on EC gel matrices were performed using a dynamic contact angle analyzer equipped with axisymmetric drop shape analysis of the sessile drop images. Gel density was determined by weighing known volumes of gel samples.
  
  
  RESULTS
  The EC gel matrices were wetted by both water and IPM, with much higher wettability by the latter. Increased EC concentration and polymeric chain length decreased the extent and rate of wetting. Linear correlation was observed between wetting parameters and rheological as well as mechanical properties of EC gel matrices.
  
  
  CONCLUSIONS
  The EC gel matrices exhibited both hydrophilic and lipophilic properties, with predominance of the latter. The extent and rate of wetting was governed by a balance of chemical and physical characteristics of the gel. EC gel matrices showed desirable wetting behavior in their function as a moisture-barrier, bioadhesive and vehicle for topical drug delivery.
authors.affiliation: Department of Pharmacy, Faculty of Science, National University of Singapore, 18 Science Drive 4, Singapor, 117543, Singapore.
authors.forename: L W
authors.initials: LW
authors.lastname: Chan
authors.forename: K T
authors.initials: KT
authors.lastname: Chow
authors.forename: P W S
authors.initials: PW
authors.lastname: Heng
mesh_terms: D000268:Adhesiveness; D002482:Cellulose / Q000031:analogs & derivatives* / Q000737:chemistry; D002626:Chemistry, Pharmaceutical; D004548:Elasticity; D005079:Excipients; D005782:Gels; D006244:Hardness; D016014:Linear Models; D008970:Molecular Weight; D013329:Structure-Activity Relationship; D013500:Surface Tension; D014783:Viscosity
chemical_list: D005079:Excipients; D005782:Gels; C013517:ethyl cellulose; D002482:Cellulose