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Controlled Release of Antidepressant Drugs by Multiple Stimuli-Sensitive Hydrogels Based on α-Aminoacid Residues
No full textTwo slightly cross-linked hydrogels bearing l-phenylalanine (Phe-Nip3) or l-valine (Ava2) residues of a copolymeric and homopolymeric vinyl structure were considered for their potential application in the psychiatric treatment of depression. Two antidepressant drugs (citalopram and trazodone) were loaded into hydrogels and their controlled release behavior monitored for several days at 25 °C in two buffer solutions of different pHs (PBS pH 7.4 and acetate pH 4.6). The different basicity constants (logKs) of the involved substance determine a different electrostatic effect between the drug ionized positively and the negatively charged hydrogel. Both the hydrogels loaded with citalopram showed a greater binding effect with respect to trazodone. In fact, for the same hydrogel, the release of citalopram in PBS (4 days) was slower than trazodone (24 h). In addition, at pH (4.6) < logK the release of the drug was much slower and durable, due to the lower capacity of ionization and swelling of the hydrogel. Additionally, the magnetic nanoparticles (CoFe2O4) embedded into the hydrogel Phe-Nip3 were an additional remote control for drug release through the stimulation of an appropriate alternating magnetic field (AMF, 20 kHz and 50 W). In these conditions, the kinetics of the drug released was substantially increased
Smart polyelectrolyte hydrogels: a novel platform for drug delivery
Full text linkThree kinds of vinyl hydrogels with a-aminoacid residues have been considered as potential platforms for the deliver of several therapies (pain, diabetes, and mood) when loaded with appropriate drugs. The presence of ionizable groups of the L-valine, L-phenylalanine and L-histidine residues is able to modify the swelling properties of the hydrogel on the basis of its pKa values. A greater basicity constant of the functional groups improves a greater loading of the drug and a longer sustained-release pattern due to a strong polymer-drug ionic interaction. This occurs for the insulin and the paroxetine loaded on carboxylate hydrogels, and diclofenac loaded on zwitterionic hydrogels. The pH stimulation improves the swelling of the hydrogel and increases ‘on demand' the drug availability. A further remote stimulus based on alternating magnetic fields (AMF) on hydrogels containing embedded magnetic nanoparticles (CoFe2O4) allows a greater release rate of insulin and paroxetine for several pulses at physiological pH
Stimuli-Responsive Hydrogels Bearing α-amino acid Residues: a Potential Platform for Future Therapies
Full text linkVinyl hydrogels bearing α-aminoacid residues have been explored as platforms for the treatment of cancer, glaucoma and mood disorder therapies. Ionic/ionizable groups of the L-valine, L-phenylalanine and L-histidine residues are able to modify the swelling properties of the hydrogel on the basis of their thermodynamic characteristics. Greater basicity constants of functional groups improve a greater loading of the drug and a longer sustained-release pattern. The pH and the temperature affect the swelling of the hydrogel and increase ‘on demand’
the drug availability. A further stimulus based on alternating magnetic fields can be applied on hydrogels containing embedded magnetic nanoparticles used for site-specific controlled drug delivery. The diffusion process for the in
vitro release of the drug (cisplatin, doxorubicin, pilocarpine, trazodone, citalopram and paroxetine) from the drugloaded hydrogels is mainly controlled by the drug-polymer interaction, that in the meanwhile preservs it’s bioactivity.
The different interaction strength between the drug and the polymer may be a strategy to develop suitable capsules for long-term therapies
Polyelectrolyte Hydrogel Platforms for the Delivery of Antidepressant Drugs
No full textSome vinyl hydrogels containing -amino acid residues (L-phenylalanine, L-valine) were
used as polyelectrolyte platforms for the evaluation of the controlled release of two antidepressants
(paroxetine and duloxetine). The closer acidity constant (pKa) values of the two drugs show a closer
release profile in physiological phosphate buffered saline (PBS) buffer (pH 7.40) and for long periods
of time. The great electrostatic interaction forces between the COO group of the hydrogel and the
protonated secondary amino nitrogen of the drug are the main factor improving the release kinetics;
this release was found to be slower compared to that of two structurally related drugs bearing the
tertiary amino nitrogen atom (citalopram and trazodone). Moreover, at the lower value of pH 4.60,
paroxetine showed a flatter release profile from the hydrogel containing the L-phenylalanine residues
that, after six days, is half of that shown by duloxetine. Further effects due to steric and hydrophobic
interactions may contribute to the different release profile. A further stimulation with alternating
magnetic fields (AMF) of low frequency (20 kHz/50 W) enhanced the release of the drug at pH 7.40
from the hydrogel containing magnetic nanoparticles. Both AMF and PBS solution at pH 7.40 were
used to trigger the ‘on-demand’ pulsatile paroxetine release from the nanocomposite hydrogel
Stimuli-responsive hydrogels for controlled pilocarpine ocular delivery
No full textA series of vinyl hydrogels containing α-aminoacid (L-histidine, L-valine) residues was synthesized and their swelling properties evaluated at different pHs and temperatures. Unlike the zwitterionic compound containing only the L-histidine, a dual-stimuli responsiveness was improved in the carboxyl acid hydrogels carrying the L-valine residues (HVa). Besides the COOH functionality, the presence of either isopropyl and amido groups in the monomer structure renders the hydrogel also temperature-responsive, in a similar manner as the well-known poly(N-isopropylacrylamide) (pNIPAAm). The three HVa hydrogels (crosslinked with 1, 2, and 5 mol% of N,N0-ethylene-bisacrylamide, EBA) show a phase separation at the same critical pH4, although a different swelling was improved by the amount of EBA. In buffered solutions, the effect of increasing temperature led to decrease the swelling and, as the pH is close to the critical one, a further and sharper collapse of the hydrogel may be tuned. The release study of pilocarpine in physiological conditions showed a burst effect within the first few hours, followed by a sustained release for a week. The initial burst effect was strongly dependent on the kind of hydrogel investigated. As the pilocarpine is a basic molecule (pK a 7.2), it may interact more strongly with the free carboxyl groups in the ionized state of the HVa hydrogels than the zwitterionic species of the histidine compounds. The releasing profile shows a three time greater release of the pilocarpine loaded in the HVa hydrogels. The hydrogels were found to be non-toxic against the mouse fibroblast NIH3T3 cells. The presence of pilocarpine strongly increased the cell proliferation even after 2 days
Long-Term Doxorubicin Release From Multiple Stimuli-Responsive Hydrogels Based on -Amino-Acid Residues
No full textWe have developed a series of pH- and temperature- stimuli-sensitive vinyl hydrogels, bearing -amino acid residues (L-phenylalanine, L-valine) and incorporating magnetic nanoparticles of different chemical compositions (CoFe2O4 and Fe3O4). The goal was to study the potential applications of these nanocomposites in the controlled release of doxorubicin (DOXO), a potent anticancer drug. The strength of the electrostatic interaction between the protonated nitrogen of the DOXO molecule and the ionized carboxylic groups of the hydrogel allowed effective control of the drug release rate in saline solutions. The embedded magnetic nanoparticles were an additional remote control of the drug release under the stimulus of an appropriate external alternating magnetic field (AMF). Data showed that the controlled release of DOXO proceeded for months and followed a diffusion-controlled release mechanism, while maintaining the amount of released drug within acceptable therapeutic windows. The amount of the released DOXO was found in all cases substantially higher than the “control” because the application of the AMF augments in stimulating the nanoparticles within the DOXO-loaded hydrogel. In vitro experiments have shown that the released DOXO is able to induce cell death to cervix adenocarcinoma cells (HeLa cells)
PTSD in victims of terroristic attacks: a comparison with the impact of other traumatic events on patients' lives
Full text linkObjectives. To identify possible differences, in terms of duration and severity of Post-Traumatic Stress Disorder, between victims of terrorist attacks and subjects who underwent other types of traumatic events. Methods. A sample of subjects suffering from PTSD was selected. After a clinical interview aimed at the collection of anamnestic data, CAPS to confirm the diagnosis of PTSD and DTS to assess frequency and severity of post-traumatic symptoms were administered. One-way ANOVA was used in order to compare the differences in the parameters analysed through the DTS scales and its clusters between the victims of terrorist attacks and patients undergone other traumatic events. Results. The duration of PTSD was 258 +/ - 144.9 months for people who underwent a terrorist attack and 41.6 +/ - 11.8 months for victims of other traumatic events. As regards the severity of the disorder, the total score of the DTS scale was 65.6 +/ - 26.9 in victims of terrorist attacks and 78.2 +/ - 28.2 in people who undergone other traumatic events. However, the difference was not statistically significant; Avoidance and Hypervigilance clusters showed an important statistical significance. Conclusions. No significant differences are present in terms of severity, showing that PTSD is a disabling disorder regardless the type of event that triggers it; however, a significant difference in terms of duration of the disorder leads to reflect on the importance of an early diagnostic process aimed toward the victims of terrorism, in order to avoid the risk of chronicity and progression to other psychiatric disorders such as depression
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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