A novel polyelectrolyte complex between amphiphilic poly (allyl amine) and sodium alginate.
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Polyelectrolytes are charge carrying polymers, when two oppositely charged polyelectrolytes are combined in a solution favouring charge expression, a polyelectrolyte complex can result. These complexes have been shown to be useful in the field of drug delivery in general. Amphiphilic polyelectrolytes contain both hydrophilic and hydrophobic groups as part of their structure; these amphiphilic polymers have shown interesting results in the field of protein and peptide delivery. Peptides and proteins are natural polyelectrolytes, and have been used in combination with other charged polymers in the delivery of peptide drugs. The oral route of delivery for peptides and proteins has many barriers, but is of great interest, due to its potential to improve patients’ adherence to medications. In this study poly (allyl amine) and sodium alginate were used to produce a polyelectrolyte complex with the peptide insulin, with a view to investigating one of a number of barriers preventing the peptides oral delivery, namely its enzymatic cleavage by α-chymotrypsin. Poly (allyl amine) was prepared from poly (allyl amine) hydrochloride, amphiphilic derivatives were prepared using palmitic acid-N-hydroxy succinamide and resulted in 3.7% and 5.1% palmitoyl grafted poly (allyl amine) based on elemental analysis. Furthermore samples were quaternised using methyl iodide and resulted in samples with degrees of quaternisation of 18% and 35% based on elemental analysis. alginate/poly (allyl amine) complexes were analysed at a number of mass ratios and using a number of techniques including dynamic light scattering, differential scanning calorimetry with hot-stage microscopy, zeta potential, and infra-red analysis. Results showed that alginate and the different derivatives of poly (allyl amine) resulted in nano-sized aggregates with estimated hydrodynamic diameters ranging from 130-400nm. Thermal analysis showed that complexation appeared to have resulted in changes in the thermal decomposition temperatures of polymers. Variations in the vibrational frequencies of infra-red results for analysed samples were used as evidence of polyelectrolyte interactions. Zeta potential of select samples resulted in values >50mV, indicating good colloidal stability of nano-aggregates. Transmission electron microscopy showed the formation of distinct spherical particles, and agglomerations of spherical and needle shaped particles. Polyelectrolyte complexes of poly (allyl amine), sodium alginate, and insulin were prepared at a different pH, but were investigated using similar methods as complexes of poly (allyl amine) and sodium alginate without insulin. Dynamic light scattering results showed the formation of complexes with estimated hydrodynamic diameters of 150-200nm. Thermal analysis showed changes in the thermal decomposition temperatures of complexes compared to individual polyelectrolytes. Infra-red analysis showed small variations in vibrational frequencies which were seen as signs of electrostatic interaction. Reverse phase high performance liquid chromatography was used in enzymatic studies to ascertain whether prepared polyelectrolyte complexes were capable of protecting insulin from the enzymatic activity of α-chymotrypsin, results showed that complexes appeared to increase the susceptibility of insulin to enzymatic cleavage, with results after 2 hours incubation with α-chymotrypsin showing <5% remaining insulin for complexes, whereas insulin control show approximately 35% remaining peptide after 2 hours in the presence of the enzyme. The polyelectrolytes used appeared to result in stable complexes maintained by a combination of electrostatic and hydrophobic interactions, however these interaction also appeared to lead to increased degradation of insulin by α-chymotrypsin.