Odunze, U; O'Brien, F; Godfrey, L; Schätzlein, A; Uchegbu, I; (2019) Unusual Enthalpy Driven Self Assembly At Room Temperature With Chitosan Amphiphiles. Pharmaceutical Nanotechnology , 7 (1) pp. 57-71. 10.2174/2211738507666190311123401.

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Text Uchegbu_GCPQ thermodynamics paper revised Oct 2018.pdf - Accepted Version Download (1MB) | Preview

Abstract

HYPOTHESIS: GCPQ (N-palmitoyl-N-monomethyl-N,N-dimethyl-N,N,N-trimethyl-6-O-glycolchitosan) is a self-assembling polymer being investigated as a pharmaceutical nano-carrier. GCPQ nanoparticles shuttle drugs across biological barriers, improving drug performance. The exact chemistry of GCPQ is varied by the relative proportion of hydrophobic (N-palmitoyl) and hydrophilic (quaternary ammonium) groups and molecular weight. We hypothesise that the thermodynamics of self-assembly is controlled by the polymer molecular weight and hydrophobicity. METHODS: The thermodynamics of self-assembly was investigated using isothermal calorimetry. FINDINGS: GCPQs (Mw = 8 - 15 kDa) formed micellar aggregates at critical micellar concentrations of 1 - 2.4 μM at 25 °C and micellisation was unusually enthalpy driven. There was a positive correlation between ΔHmic and Q: ΔHmic = 3.8 Q - 159 (r2 = 0.93) and a negative correlation between ΔHmic and molecular weight (Mw): ΔHmic = -13.5 Mw - 26.3 (r2 = 0.99). These findings provide insights into the positive drivers of stable self-assemblies, namely hydrophobicity and molecular weight, as both hydrophobicity and molecular weight are associated with an increased enthalpy contribution to micellisation.

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