title: Insights into hydrophobic molecule release from polyelectrolyte multilayer films using in situ and ex situ techniques.
abstract: We report on the loading and release of curcumin (a hydrophobic polyphenol with anti-inflammatory and anti-bacterial properties) from polyelectrolyte multilayers composed of poly(diallyldimethylammonium chloride) (PDADMAC) and poly(sodium 4-styrenesulfonate) (PSS). We have used the in situ techniques of attenuated total reflectance (ATR) FTIR spectroscopy and quartz crystal microbalance with dissipation monitoring (QCM-D) to study the formation of the PEM and the incorporation of curcumin, providing direct evidence of the incorporation, in terms of molecular vibrations and gravimetric detection. The release of curcumin was followed using ex situ measurements of UV-visible spectroscopy of PEM films on quartz plates, in addition to in situ ATR FTIR measurements. Release was studied as a function of salt concentration of the release solution (0.001 M NaCl; 1 M NaCl). UV-visible spectroscopy indicated that salt concentration of the release solution had a major impact on release rates, with higher salt giving faster/more extensive release. However, prolonged timescale immersion and monitoring with UV-visible spectroscopy indicated that sample dehydration/rehydration cycling (required to measure UV absorbance) was responsible for the release of curcumin, rather than immersion time. In situ measurements of release kinetics with ATR FTIR confirmed that release does not occur spontaneously while the multilayer remains hydrated.
authors.affiliation: Ian Wark Research Institute, University of South Australia, Mawson Lakes Campus, Mawson Lakes, SA 5095, Australia. David.Beattie@unisa.edu.au.
authors.forename: Yongjin
authors.initials: Y
authors.lastname: Shin
authors.forename: Weng Hou
authors.initials: WH
authors.lastname: Cheung
authors.forename: Tracey T M
authors.initials: TT
authors.lastname: Ho
authors.forename: Kristen E
authors.initials: KE
authors.lastname: Bremmell
authors.forename: David A
authors.initials: DA
authors.lastname: Beattie
mesh_terms: D004573:Electrolytes / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D015394:Molecular Structure; D011095:Polyethylenes / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D058525:Quartz Crystal Microbalance Techniques; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013451:Sulfonic Acids / Q000737:chemistry*
chemical_list: D004573:Electrolytes; D011095:Polyethylenes; D011108:Polymers; D000644:Quaternary Ammonium Compounds; D013451:Sulfonic Acids; C041004:poly-N,N-dimethyl-N,N-diallylammonium chloride; C077114:styrenesulfonic acid polymer