Abstract
Thin films were prepared using layer-by-layer (LbL) deposition of Nafion (NAF) and polycations such as poly(allylamine hydrochloride) (PAH), poly(ethyleneimine) (PEI), and poly(diallydimethylammonium chloride) (PDDA). Insulin was then adsorbed on the NAF-polycation LbL films by immersion in an insulin solution. The NAF-polycation LbL films were characterized using a quartz crystal microbalance and an atomic force microscope. The release of insulin from the LbL films was characterized using UV-visible adsorption spectroscopy and fluorescence emission spectroscopy. The greatest amount of insulin was adsorbed on the NAF-PAH LbL film. The amount of insulin adsorbed on the (NAF/PAH)5NAF LbL films by immersion in a 1 mg mL−1 insulin solution at pH 7.4 was 61.8 µg cm−2. The amount of insulin released from the LbL films was higher when immersed in insulin solutions at pH 2.0 and pH 9.0 than at pH 7.4. Therefore, NAF-polycations could be employed as insulin delivery LbL films under mild conditions and as an insulin release control system according to pH change.
Highlights
Layer-by-layer (LbL) films can be prepared by alternate and repeated deposition of a polyelectrolyte on a solid surface through electrostatic interactions [1,2]
The value of −∆F was increased when the quartz resonator was exposed to NAF and poly(allylamine hydrochloride) (PAH), PEI, or poly(diallydimethylammonium chloride) (PDDA), which indicated that NAF-PAH, NAF-PEI, and NAF-PDDA
It is considered that negatively charged NAF and positively charged PAH, PEI, and PDDA are deposited by electrostatic attraction, which builds up the LbL film on the quartz resonator surface
Summary
Layer-by-layer (LbL) films can be prepared by alternate and repeated deposition of a polyelectrolyte on a solid surface through electrostatic interactions [1,2]. The materials employed for this purpose include synthetic polymers [8,9,10], proteins [11], polysaccharides [12,13], and DNA [14]. Such layered thin films have found applications in separation and purification [15,16], sensors [17,18,19], microcapsules [20,21], and drug delivery systems (DDSs) [22,23]. LbL based DDS that responds to pH [24,25,26] and sugar levels [27,28,29,30].
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