M. Dolores Blanco

5-Fluorouracil release from copolymeric hydrogels of itaconic acid monoester. I. Acrylamide-co-monomethyl itaconate.

The aim of this work was to test the application of new copolymeric poly (acrylamide-co-monomethyl itaconate) (A/MMI) hydrogels to 5-fluorouracil (5-FU) release. Three different compositions of copolymers have been studied, 90A:10MMI 75A:25MMI and 60A:40MMI. The equilibrium swelling degree in saline solution was between 76 and 80% depending on the copolymer composition. 5-FU, as the sodium salt, was trapped in the gels by including it in the feed mixture of polymerization. The swelling kinetics of the hydrogels in saline solution were studied at four temperatures, and the diffusion coefficient and the activation energy of the process were obtained. The 5-FU release as a function of temperature and disc load was studied; the diffusion coefficient and the activation energy of the release process were also obtained. The diffusion studies follow Ficks second law.

Influence of degree of crosslinking on 5-fluorouracil release from poly(2-hydroxyethyl methacrylate) hydrogels.

Controlled release of 5-fluorouracil (5-FU) from poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels with three different degrees of crosslinking is reported. The swelling kinetic of PHEMA hydrogels in water was studied at different disc thicknesses and temperatures, and the diffusion coefficient and activation energy of the process were obtained. The gels were loaded with 5-FU by immersing them in concentrated aqueous solutions of the drug. The 5-FU release was studied as a function of temperature, disc thickness, disc load and degree of crosslinking of the gels; the diffusion coefficient and activation energy of the release process were also obtained.

Controlled release of cytarabine from poly(2-hydroxyethyl methacrylate-co-N-vinyl-2-pyrrolidone) hydrogels

Controlled release of cytarabine (ara-C) from poly(2-hydroxyethyl methacrylate-co-N-vinyl-2-pyrrolidone) [p(HEMA-co-VP)] hydrogels cross-linked with ethylene glycol dimethacrylate (EGDMA) is reported. Three compositions of copolymer, each one with a different cross-linking degree, have been studied: H50/VP50, H75/VP25, and H80/VP20. Ara-C (5-25 mg by disc) was trapped in the gels by including it in the polymerization feed mixture. The ara-C release time was between 1 day from H50/VP50/E0.5 discs and 16 days from H80/VP20/E15 discs. In all cases there is a time period for which the drug release rate is constant.

Release of 5-fluorouracil from poly(acrylamide-co-monopropyl itaconate) hydrogels

The aim of this work was to test the application of copolymeric poly(acrylamide-co-monopropyl itaconate) (A-MPI) hydrogels on the release of 5-fluorouracil (5-FU). The equilibrium degree of swelling in saline solution was 83 +/- 2%. 5-FU, as the sodium salt, was trapped in gels by placing it in the polymerization feed mixture. The diffusion coefficients for both swelling of the gels and the release of 5-FU were determined, in addition to the activation energies for both processes. To determine the applicability of these copolymers, A-MPI (75:25) gel was subcutaneously implanted in rats and the drug plasma concentration was determined by HPLC.

Skin laser treatments enhancing transdermal delivery of ALA.

Drug delivery across skin has been limited due to barrier properties of the skin, especially those of the stratum corneum (SC). Use of the laser radiation has been suggested for the controlled removal of the SC. The purpose of this study was to study in vitro the influence of infrared radiation from the erbium:yttrium-aluminum-garnet (Er:YAG) laser (λ = 2940  nm), and visible from the 2nd harmonic of a neodymium:yttrium-aluminum-garnet (Nd:YAG) laser (λ = 532  nm) on transdermal delivery of 5-aminolevulinic acid (ALA). Pinna skin of the inner side of rabbit ear was used for skin permeation. The light sources were an Er:YAG laser (Key III Plus KaVo) and a Q-switched Nd:YAG laser (Lotis TII SL-2132). Permeation study, morphological and structural skin examination by histology and differential scanning calorimetry (DSC) were carried out. Permeation profiles and histological observations obtained after irradiation with infrared and visible laser radiation differed due to different biophysical effects on irradiated skin. Wavelength of 2940  nm required lower energy contribution to produce the same level of permeation than visible radiation at 532  nm. Structural analysis by DSC shows a selective impact on the lipidic structure. Laser pretreatment enhanced the delivery of ALA trough the skin by SC ablation.

l-Ascorbic acid release from phema hydrogels

Controlled release of L-ascorbic acid from poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels is reported. PHEMA hydrogels were synthesized from 2-hydroxyethyl methacrylate (HEMA) monomer in an oven. We studied the swelling of PHEMA discs in water as a fuction of temperature and thickness of xerogel discs. The fractional swelling was linear in (time)1/2 at short times. Drug release has been examined as a fuction of temperature, initial drug load and thickness of the PHEMA discs. The fraction of avaible drug release was linear in (time)1/2 during the initial stage too. The release experiments were carried out at 308 K. These studies allow to determinate a diffusion coefficient for transport of water into the hydrogels and a diffusion coefficient for L-ascorbic acid release from the hydrogel.

Tamoxifen-loaded folate-conjugate poly[(p-nitrophenyl acrylate)-co-(N-isopropylacrylamide)] sub-microgel as antitumoral drug delivery system

Folate-conjugate poly[(p-nitrophenyl acrylate)-co-(N-isopropylacrylamide)] sub-microgel (F-SubMG) was loaded with tamoxifen (TMX) to obtain low (9.0 ± 0.4 μg TMX/mg F-SubMG) and high (112.0 ± 15.0 μg TMX/mg F-SubMG) load TMX-loaded F-SubMGs. Maximum in vitro drug release (77 ± 2% to 90 ± 2% of loaded TMX) took place between 47 and 168 h. The cytotoxicity of unloaded F-SubMGs in MCF-7 and HeLa cells was low; although it increased for high F-SubMG concentration. The administration of 10 μM TMX by TMX-loaded F-SubMGs was effective on both cellular types. Cell uptake of F-SubMGs took place in both cell types, but it was larger in HeLa cells because they are folate receptor positive. After subcutaneous administration (2.8 mg TMX/kg b.w.) in Wistar rats, F-SubMGs were detected at the site of injection under the skin, and a significant amount of them were included inside adipocytes. Signs of rejection were not observed after 60 days of injection. Pharmacokinetic study showed an increase in mean residence time of TMX and 4-hydroxytamoxifen (4-OHTMX), as well as a metabolite ratio (MR = AUC(4OHTMX) /AUC(TMX) ) nine times larger, when TMX was administered by drug-loaded F-SubMGs. Since 4-OHTMX is a more potent (at least 100-fold higher) antiestrogen than TMX, administration of TMX-loaded F-SubMGs can be considered an advantage.

Bioresponsive nanohydrogels based on HEAA and NIPA for poorly soluble drugs delivery

Environmentally sensitive hydrogels have gained considerable attention in recent years as one of the most promising drug delivery systems. In the present study, two new formulations of pH and temperature stimuli-responsive nanogels (NGs) based on poly-N-isopropylacrylamide (NIPA), N-hydroxyethyl acrylamide (HEAA) and tert-butyl 2-acrylamidoethyl carbamate (2AAECM) were synthesized and evaluated for passive targeting of paclitaxel (PTX). Nanogels were prepared by microemulsion polymerization method using N-methylenebis(acrylamide) (NMBA) as crosslinking agent. TEM images and DLS results showed nanosized spherical hydrogels. FTIR spectra confirmed the synthesis of nanogels by radical polymerization among vinyl groups of monomers. The PTX loading capacity, encapsulation efficiency and in vitro release were analyzed by HPLC. The cumulative release profile of the PTX-loaded nanohydrogels within 144h showed a faster drug release at acid pH (pH 5), similar to those observed at lysosome compartment, whereas a fewer PTX amount was released from NGs at pH similar to plasma levels. Cellular uptake assays revealed rapid penetration and intracellular accumulation of those nanogels in MCF7, HeLa and T47D cells after 48h incubation. MTT assays showed cell viability dependence on concentration and time incubation. Finally, the PTX effect on cell viability showed a G2/M cell arrest after using PTX-loaded NGs and pure PTX.

Tamoxifen-loaded nanoparticles based on a novel mixture of biodegradable polyesters: characterization and in vitro evaluation as sustained release systems

Nanoparticles (NP) from mixtures of two poly(D,L-lactide-co-caprolactone) (PLC) copolymers, PLC 40/60 and PLC 86/14, with poly(D,L-lactide) (PDLLA) and PCL were prepared: PLC 40/60-PCL (25:75), PLC 86/14-PCL (75:25) and PLC 86/14-PLA (75:25). Tamoxifen was loaded with encapsulation efficiency between 65% and 75% (29.9–36.3 µg TMX/ mg NP). All selected systems showed spherical shape and nano-scale size. TMX-loaded NPs were in the range of 293–352 nm. TMX release from NP took place with different profiles depending on polymeric composition of the particles. After 60 days, 59.81% and 82.65% of the loaded drug was released. The cytotoxicity of unloaded NP in MCF7 and HeLa cells was very low. Cell uptake of NP took place in both cell types by unspecific internalization in a time dependent process. The administration of 6 and 10 µm TMX by TMX-loaded NP was effective on both cellular types, mainly in MCF7 cells.

Biocompatibility evaluation of pH and glutathione-responsive nanohydrogels after intravenous administration.

Nanotoxicology has emerged as an important subdiscipline of nanotechnology due to the new healthy risks associated with the use of nanosystems for therapy and diagnostic. The biocompatibility of four stimuli-responsive nanohydrogel (NG) formulations based on different proportions of N-isopropylacrylamide (NIPA), N-hydroxyethyl acrylamide (HEAA) and 2-acrylamidoethyl carbamate (2AAECM), and cross-linked with N,N-cystaminebisacrylamide (CBA) or N-methylenebisacrylamide (NMBA) has been evaluated after intravenous injection in Wistar rats. All nanohydrogels were pH-sensitive, and those with CBA were also glutathione-responsive. Haematological and coagulation parameters revealed most nanogel formulations did not cause modification, only the NHA 80/15/5-CBA formulation induced a transitory light increase in platelets. Prothrombin time was in the reference normal range, there were no modifications of fibrinogen concentration and an increase in antithrombin III was observed on the last day of the study. Blood biochemical parameters such as AST, ALT, ALP, BUN, and creatinine were in the standard range for rats. The activity of enzyme antioxidant defences (SOD, CAT and GSSG-R) and total glutathione were evaluated in liver, kidney and spleen samples. Nanohydrogels cross-linked with the disulphide reducible CBA-cross-linker caused a decrease in GSSG/GSH content and an increase in GSSG-R activity in the spleen. The antioxidant response is also reflected by modifications of SOD activity in liver and kidney of NHA 80/15/5-CBA and NHA 80/10/10-NMBA groups. Histology showed no tissue damage, inflammation or morphological change in liver, kidney and spleen. Overall, the results demonstrated modifications of antioxidant defences; however, no acute or very significant changes in biomarkers of liver or kidney damage were observed.