Conventional and Fast Field Cycling Relaxometry Study of the Molecular Dynamics in Polymer Nanocomposites for Use as Drug Delivery Systems

MARIANA MONTEIRO; FABIAN VACA CHAVEZ; PEDRO J. SEBASTIÃO; ELTON RODRIGUES; LUCIANA BRITO; MARIA INES BRUNO TAVARES

JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY

AMER SCIENTIFIC PUBLISHERS

Lugar: California; Año: 2016 vol. 16 p. 7539 - 7549

1533-4880

This article presents a molecular dynamics study performed by combining conventional and fast-fieldcycling NMR relaxation techniques in nanocomposite systems for the optimization of drug deliverysystems. The biodegradable polymers polycaprolactone, polylactide, polyvinyl alcohol and maizestarch were used as base polymers and they were modified by incorporation of nanoparticles and/orcross-linking reactions, in order to understand the interaction between the bioactive molecules andthe supporting matrix for a controlled drug release. Nevirapine was used as a testing bioactivedrug. H spin-lattice relaxation times were measured for Larmor frequencies between 10 kHz and300 MHz to obtain information about molecular motions in different time scales for comprehensiveanalysis of the possible interactions of the polymer matrices, modified nanoparticles and bioactivemolecules. All systems presented some degree of crystallinity and poly-exponential decay of magnetizationin the spin-lattice relaxation. The shortest spin-lattice relaxation times were assigned tothe more amorphous regions and the relaxation dispersion was similar to that found in polymermelts. The effects of both nanoparticles and bioactive molecules on the molecular dynamics ofthe polymer matrices were clearly detected. The results show that NMR relaxometry study coversa broad range of frequencies and it is a powerful and suitable method to characterize nanocompositesystems at the molecular scale, provides information about the mobility of polymer chainsand the strength of the interaction between polymers/nanoparticles. This information helps to makeinferences about drug confinement level inside the systems, which can have a direct influence onthe drug release. It is extremely important to know the exact drug release mechanism of bioactivemolecules in a medical treatment. The main results indicated that the NMR techniques used wereable to evaluate the molecular dynamics of the nanocomposites studied. It can be pointed out thatPCL/clay nanocomposites containing nevirapine drug, caused a compensating effect regarding tothe distribution of correlation times for the molecular segment motions and the drugs interferes inthe nanomaterial molecular dynamics.