Metformin hydrochloride is an extensively used antidiabetic drug that according to the results reported here is able to spontaneously intercalate layered silicates like the montmorillonite clay mineral following an ion-exchange mechanism. The adsorption isotherm from water solutions shows a great affinity of metformin towards the clay mineral, which can retain about thrice the exchange capacity of the clay. The adsorbed excess was easily removed by washing with water, leading to an intercalation compound that contains 93 meq of metformin per 100 g of montmorillonite, matching the CEC value of this clay. The intercalated metformin is arranged in the interlayer space as a monolayer of monoprotonated molecules, which remain strongly entrapped within the solid. These new hybrid materials were characterized by elemental chemical analysis, XRD, FTIR, TG-DTA, and NMR. We preliminary evaluated the use of the metformin-montmorillonite intercalation compound as a drug delivery system, determining the liberation kinetics of metformin at diverse pH values that mimic the gastrointestinal tract. Although the release rate was not totally slowed down, the system seems promising in view of further optimization for drug delivery applications.
The
present work introduces new functional bionanocomposite materials
based on layered montmorillonite and fibrous sepiolite clays and two
biopolymers (carboxymethylcellulose polysaccharide and zein protein)
to produce drug-loaded bionanocomposite films for antibiotic topical
delivery. Neomycin, an antibiotic indicated for wound infections,
was employed as the model drug in this study. The physical properties
and the antimicrobial activity of these materials were evaluated as
a function of the type of hybrid and the amount of zein protein incorporated
in the bionanocomposite films. In addition, the interfacial and physicochemical
properties of these new clay–drug hybrids have been studied
through a combination of experimental and computational methodologies,
where the computational studies confirm the intercalation of neomycin
into the montmorillonite layers and the possible penetration of the
drug in the tunnels of sepiolite, as pointed out by N
2
adsorption
and X-ray diffraction techniques. The antimicrobial activity of these
bionanocomposite materials show that the films based on montmorillonite–neomycin
display a more pronounced inhibitory effect of the bacterial growth
than those prepared with the sepiolite–neomycin hybrid. Such
effect can be related to the difficult release of neomycin adsorbed
on sepiolite due to a strong interaction between both components.
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