119 research outputs found
Clay-biosurfactant materials as functional drug delivery systems: Slowing down effect in the in vitro release of cinnamic acid
The main objectives of the present paper were the preparation and characterization of new surfactant-modified clays and the evaluation of their potential applicability as drug delivery systems for the oral administration of the cinnamic acid (CA) drug. The organoclays (OC) were prepared by loading different amounts of the biocompatible nonionic polyoxyethylene sorbitan monolaurate surfactant (Tween20) onto K10 montmorillonite (Mt) clay and characterized through the construction of the adsorption isotherms by means of the spectrophotometric method.
The performance of the prepared material was verified by gathering the adsorption isotherms of the cinnamic acid onto the Mt/Tween20 organoclay and by monitoring the release profiles in both simulated gastric (SGF) and intestinal fluids (SIF).
The quantitative analysis of the adsorption isotherms revealed that the uptake of the aromatic component onto both the blank and Tween20-loaded Mt was governed by positive cooperative processes and that the presence of the bio-surfactant enhanced the loading efficiency of the clay.
By relating the raw montmorillonite uptake capability with that of the OC it was assessed that the presence of the bio-surfactant enhanced about 2 times the loading efficiency of the clay. From the XRD characterization of the obtained complexes, the successful intercalation of the drug into the prepared organoclay was demonstrated.
Very useful information was obtained by the in vitro release studies, which showed that the release of the drug from both the clay and organoclay was prolonged in comparison with the pharmacokinetics of the free drug. Besides, the intercalation of the surfactant into the nano-carrier ensured the complete release of the CA after oral drug administration and the kinetics of the release process was strongly dependent on the type of drug formulation used, which means that the CA release can be modulated by properly functionalizing the clay surface
Peculiar Mechanism of Solubilization of a Sparingly Water Soluble Drug into Polymeric Micelles. Kinetic and Equilibrium Studies
Complementary kinetic and equilibrium studies
on the solubilization process of the sparingly water soluble
tamoxifen (TAM) drug in polymeric aqueous solutions have
been performed by using the spectrophotometric method. In
particular, the amphiphilic copolymers obtained by derivatization
of polymeric chain of poly(N-2-hydroxyethyl)-DLaspartamide,
PHEA, with poly(ethylene glycol)s, PEG (2000
or 5000 Da), and/or hexadecylamine chain, C16, namely
PHEA-PEG2000-C16, PHEA-PEG5000-C16, PHEA-C16, have
been employed. Preliminary to the kinetic and equilibrium
data quantitative treatment, the molar absorption coefficient of
TAM in polymeric micelle aqueous solution has been
determined. By these studies the solubization sites of TAM
into the polymeric micelles have been determined and the solubilization mechanism has been elucidated through a
nonconventional approach by considering the TAM partitioned between three pseudophases, i.e., the aqueous pseudophase, the
hydrophilic corona, and the hydrophobic core. The simultaneous solution of the rate laws associated with each step of the
proposed mechanism allowed the calculation of the rate constants associated with the involved processes, the values of which are
independent of both the copolymer concentration and nature, with the exception of the rate of the TAM transfer from the
corona to the core. This has been attributed to the steric barrier, represented by the corona, which hampers the solubilization
into the core. The binding constant values of the TAM to the hydrophilic corona of the polymeric micelles, calculated through
the quantitative analysis of the equilibrium data, depend on the thickness of the hydrophilic headgroup, while those of the
hydrophobic core are almost independent of the copolymer type. Further confirmation to the proposed solubilization mechanism
has been provided by performing the kinetic and equilibrium measurements in the presence of PHEA-PEG2000 and PHEAPEG5000
copolymers
Modified montmorillonite as drug delivery agent for enhancing antibiotic therapy
The appealing properties of surfactant‐intercalated Montmorillonites (Organo-montmorillonite, OMt) were successfully investigated to propose an effective drug delivery system for metronidazole (MNE) antibiotic therapy. This represents a serious pharmaceutical concern due to the adverse drug reactions and the low targeting ability of MNE. The non‐ionic surfactant Tween 20 was used to functionalize montmorillonite, thus accomplishing the two‐fold objective of enhancing the stability of clay dispersion and better controlling drug uptake and release. The adsorption process was performed under different experimental conditions and investigated by constructing the adsorption isotherms through high‐performance liquid chromatography (HPLC) measurements. Powder X‐ray diffraction (XRD) measurements were performed to characterize the MNE/OMt compounds. The gathered results revealed that the uptake of the drug occurs preferentially in the clay interlayer, and it is governed by positive cooperative processes. The presence of surfactant drives the adsorption into clay interlayer and hampers the adsorption onto external lamella faces. The good performances of the prepared OMt in the controlled release of the MNE were proved by investigating the release profiles under physiological conditions, simulating oral drug administration. Cytotoxicity measurements demonstrated the biocompatibility of the complexes and evidenced that, under specific experimental conditions, nanodevices are more biocompatible than a free drug
Sodium bis-(2-ethylhexyl) sulfosuccinate sepf-aggregation in vacuo: Molecular Dynamics simulation
Molecular dynamics (MD) simulations were conducted for systems in vacuo consisting of n AOT
anions (bis(2-ethylhexyl)sulfosuccinate ions) and n 1 or n Na+ ions up to n = 20. For n = 15,
positively charged systems with Li+, K+, and Cs+ cations were also considered. All systems were
observed to form reverse micelle-like aggregates whose centre is occupied by cations and polar
heads in a very compact solid-like way, while globally the aggregate has the form of an elongated
and rather flat ellipsoid. Various types of statistical analyses were carried out on the systems to
enlighten structural and dynamical properties including gyration radius, atomic pair correlation
functions, atomic B-factor and moment of inertia tensor. For completeness and comparison the
stability of reverse micelle is tested in the case of neutral n = 20 system in CCl4 solution
COUPLING ELECTROCHEMISTRY TO ELECTROSPRAY: A NOVEL PREPARATION OF GOLD NANOSTRUCTURES
nanoparticles on ITO (Indium tin oxide) coated glass using the electrospray (ESI) method
Method:The starting point of this study is that the ESI/MS spectrum (Figure 1) of an ethanolic
solution of HAuCl 4 shows a reduction process of Au (III) strongly dependent on the Cone Voltage
(CV) values (20, 80, 150 V), affording to the ion at m/z 197 (Au+). Further, the decrease of the
abundance of this ion at the highest cone voltage suggests the subsequent its reduction with the
formation of Au
0
.
Figure 1: ESI/MS spectra of an ethanolic solution of HAuCl4 at various cone voltages:
Conclusion: Such experimental evidence leads us to use electrospray technique as a preparative
tool to obtain the formation and deposition of gold nanoparticles in a single step.
In fact, using a home-made electrospray apparatus, we sprayed an ethanolic solution of HAuCl4,
forming a very thin aerosol that has been uniformly deposited on ITO coated glass.
Then, the deposit by SEM, UV-Vis, Optical-Microscopy and XPS has been characterized4,5. In
particular, SEM micrographs show rod-like structures, while XPS spectra show that the deposited
nanoparticles contain about 23% of Au0
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