José M. Teijón

Laser treatments on skin enhancing and controlling transdermal delivery of 5-fluorouracil.

Laser ablation of stratum corneum (SC) enhances transdermal delivery of hydrophilic drugs. The influence of the infrared (IR) (λ = 1,064 nm), visible (λ = 532 nm), and ultraviolet (UV) (λ = 355 nm) radiations of a Nd:YAG laser on transdermal delivery of 5‐Fluorouracil (5‐Fu) across skin was studied in vitro.

Use of Poly(N‐isopropylacrylamide) Nanohydrogels for the Controlled Release of Pimaricin in Active Packaging

UNLABELLED We propose here a delivery drug-polymer system using poly(N-isopropylacrylamide) (PNIPA) nanohydrogels that enables pimaricin to be protected from hostile environments and allows the controlled release of the antifungal through environmental stimuli. We synthesized 2 nanohydrogels, 1 with 100% N-isopropylacrylamide (PNIPA(5)) and 1 with 80% N-isopropylacrylamide copolymerized and 20% acrylic acid (PNIPA-20AA(5)). Both were then, loaded with a pimaricin aqueous solution. The pimaricin release profiles of these 2 nanohydrogels were considerably different: PNIPA(5) released 10% and PNIPA-20AA(5) released 30% with respect to the free pimaricin release. Moreover, the diffusion experiments showed that pimaricin was released from the PNIPA-20AA(5) nanohydrogel for up to 3 times longer than free pimaricin. Therefore, incorporating acrylic acid as comonomer into the PNIPA nanohydrogel resulted in a slower but more continuous release of pimaricin. The highest pimaricin levels were reached when the most hydrophilic nanohydrogel was used. The bioassay results showed that the pimaricin-nanohydrogel system was highly effective in inhibiting the growth of the indicator strain in conditions of thermal abuse. The spoilage in acidified samples stored under fluorescent lighting was reduced by 80.94% ± 33.02% in samples treated with a pimaricin-loaded nanohydrogel, but only by 19.91% ± 6.68% in samples treated with free pimaricin. Therefore, 2 conclusions emerge from this study. One is that the nanohydrogel delivery system could impede the degradation of pimaricin. The other is that the inhibitory effect of the antifungal on yeast growth is more pronounced when it is added included into the nanohydrogel to the food, especially in an acidic environment. PRACTICAL APPLICATION This article presents relevant results on the use of nanohydrogels in food packaging. Nanohydrogels could provide protection so that the pimaricin remains active for a longer time. They also allow the controlled release of pimaricin, which thus regulates the unnecessary presence of the antifungal in the food.

Effects of lead administration at low doses by different routes on rat spleens. Study of response of splenic lymphocytes and tissue lysozyme

The aim of this study was to evaluate the effects of low doses of lead (200 ppm of PbAc(2) for 4 weeks) on rat spleens using different routes of administration. The study has been carried out at different levels: a histological evaluation has been made, and alterations of cell proliferation, B and T lymphocyte subpopulations, and CD4(+) and CD8(+) T cell subpopulations have been evaluated. Apoptosis and necrosis of lymphoid cells were also analysed. Furthermore, lysozyme activity was measured. Results indicate a large increase in spleen size when lead is administered by intraperitoneal injection, being this route in which lead causes larger modifications in all of the parameters measured. Lead administered orally causes histological modifications, such as an increase in the number of lymphocytes as well as edema. However, significant alterations in other parameters studied have not been detected. Lead administration by intraperitoneal route causes more evident histological modifications as well as an increase in the number of lymphocytes, and also induces a decrease in the percentage of B(+), T(+) and CD4(+) cells, and an increase in CD8(+) cells. Cell death of splenic lymphocytes is not altered by lead. With regard to the immune innate response, lead behaves as an immunomodulator as can be deduced from data on lysozyme activity in tissue. Therefore, it is possible to affirm that the effect of low doses of lead depends on the route of administration. Thus, the intraperitoneal route, through which lead goes directly to the bloodstream, causes drastic effects, generating important immunological alterations.

Cooperative effect of 5-aminolevulinic acid and gold nanoparticles for photodynamic therapy of cancer

An enhanced capacity for protoporphyrin IX (PpIX) synthesis through 5-aminolevulinic acid (ALA) administration has been reported in cancer cells. We compared the effect of ALA and ALA combined with gold nanoparticles (ALA-AuNPs) for photodynamic therapy (PDT) on human cervical cancer cell line. Because PpIX after photoactivation produces reactive oxygen species (ROS), ALA-AuNPs combinations can enhance this production and then induce higher phototoxicity. With this aim, two different-sized AuNPs (14 and 136 nm, AuNP1 and AuNP2, respectively) were successfully synthesized and characterized by UV-visible spectrophotometry and transmission electron microscopy. AuNPs were combined with ALA to evaluate their cooperative action in the intracellular ROS production, cell viability, and cell death mechanism. Results showed that ALA-AuNPs combinations induced cell death via ROS-mediated apoptosis after PDT. When exposed to light at their resonance wavelength, AuNP2 combined with ALA result in cytotoxicity and cell injury in greater extension than ALA and ALA-AuNP1 combination.

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.

Studies of cadmium binding to hexokinase: structural and functional implications.

The interaction between cadmium and yeast hexokinase was studied. Cadmium produces changes in the aggregation state of the protein and large structures with a large molecular mass were formed. This phenomenon occurs without large modifications to the secondary structure. During this change the enzyme maintains a high level of activity in the monomer as well as in aggregate form. This implies that the enzyme function is not greatly affected by the change and it maintains its active sites without significant modifications. According to kinetic measurements with both glucose and ATP as a variable substrate, cadmium causes a mixed-type inhibition with a main uncompetitive component. Binding experiments show that the protein presents negative cooperative binding with cadmium at various temperatures (298, 303 and 313 K) and a progressive loss in metal union with concentration depending on the temperature. The total union percentage decreases as the metal concentration increases. This is probably due to the aggregation process, which affects the binding sites for the metal and also for the substrate. Labile interactions are more persistent than specific interactions in accordance with the solvation parameter.