title: Encapsulation of albumin in self-assembled layer-by-layer microcapsules: comparison of co-precipitation and adsorption techniques.
abstract: OBJECTIVE
  The objective of this study is to prepare and characterize polymeric self-assembled layer-by-layer microcapsules (LbL-MC) to deliver a model protein, bovine serum albumin (BSA). The aim is to compare the BSA encapsulation in LbL-MC using co-precipitation and adsorption methods.
  
  
  METHODS
  In co-precipitation method, BSA was co-precipitated with growing calcium carbonate particles to form a core template. Later, poly(styrene sulfonate) and poly(allylamine hydrochloride) were sequentially adsorbed onto the CaCO3 templates. In adsorption method, preformed LbL-MC were incubated with BSA and encapsulation efficiency is optimized for pH and salt concentration. Free and BSA-encapsulated LbL-MC were characterized using Zetasizer, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy and differential scanning calorimeter. Later, in vitro release studies were performed using dialysis membrane method at pH 4, 7.4 and 9.
  
  
  CONCLUSIONS
  Results from Zetasizer and SEM showed free LbL-MC with an average size and zeta-potential of 2.0 ± 0.6 μm and 8.1 ± 1.9 mV, respectively. Zeta-potential of BSA-loaded LbL-MC was (-)7.4 ± 0.7 mV and (-)5.7 ± 1.0 mV for co-precipitation and adsorption methods, respectively. In adsorption method, BSA encapsulation in LbL-MC was found to be greater at pH 6.0 and 0.2 M NaCl. Co-precipitation method provided four-fold greater encapsulation efficiency (%) of BSA in LbL-MC compared with adsorption method. At pH 4, the BSA release from LbL-MC was extended up to 120 h. Polyacrylamide gel electrophoresis showed that BSA encapsulated in LBL-MC through co-precipitation is stable toward trypsin treatment.
  
  
  CONCLUSIONS
  In conclusion, co-precipitation method provided greater encapsulation of BSA in LbL-MC. Furthermore, LbL-MC can be developed as carriers for pH-controlled protein delivery.
authors.affiliation: Department of Pharmacy, BITS Pilani, Hyderabad Campus , Hyderabad, Andhra Pradesh , India.
authors.forename: Suman
authors.initials: S
authors.lastname: Labala
authors.forename: Praveen Kumar
authors.initials: PK
authors.lastname: Mandapalli
authors.forename: Shubhmita
authors.initials: S
authors.lastname: Bhatnagar
authors.forename: Venkata Vamsi Krishna
authors.initials: VV
authors.lastname: Venuganti
mesh_terms: D000327:Adsorption; D000818:Animals; D002214:Capsules; D002417:Cattle; D011232:Chemical Precipitation; D004337:Drug Carriers / Q000737:chemistry* / Q000493:pharmacokinetics; D010316:Particle Size; D012710:Serum Albumin, Bovine / Q000737:chemistry* / Q000493:pharmacokinetics
chemical_list: D002214:Capsules; D004337:Drug Carriers; D012710:Serum Albumin, Bovine
keywords: Adsorption; bovine serum albumin; co-precipitation; layer-by-layer microcapsules; pH responsive