High-speed electrically actuated elastomers with strain greater than 100%

Electrical actuators were made from films of dielectric elastomers (such as silicones) coated on both sides with compliant electrode material. When voltage was applied, the resulting electrostatic forces compressed the film in thickness and expanded it in area, producing strains up to 30 to 40%. It is now shown that prestraining the film further improves the performance of these devices. Actuated strains up to 117% were demonstrated with silicone elastomers, and up to 215% with acrylic elastomers using biaxially and uniaxially prestrained films. The strain, pressure, and response time of silicone exceeded those of natural muscle; specific energy densities greatly exceeded those of other field-actuated materials. Because the actuation mechanism is faster than in other high-strain electroactive polymers, this technology may be suitable for diverse applications.

Polymer light-emitting electrochemical cells

A device configuration for light emission from electroactive polymers is described. In these light-emitting electrochemical cells, a p-n junction diode is created in situ through simultaneous p-type and n-type electrochemical doping on opposite sides of a thin film of conjugated polymer that contains added electrolyte to provide the necessary counterions for doping. Light-emitting devices based on conjugated polymers have been fabricated that operate by the proposed electrochemical oxidation-reduction mechanism. Blue, green, and orange emission have been obtained with turn-on voltages close to the band gap of the emissive material.

Light-Activatable Red Blood Cell Membrane-Camouflaged Dimeric Prodrug Nanoparticles for Synergistic Photodynamic/Chemotherapy

Biomimetic approach offers numerous opportunities to design therapeutic platforms with enhanced antitumor performance and biocompatibility. Herein we report red blood cell membrane-camouflaged nanoparticles (RBC(M(TPC-PTX))) for synergistic chemo- and photodynamic therapy (PDT). Specifically, the inner core is mainly constructed by reactive oxygen species (ROS)-responsive PTX dimer (PTX₂-TK) and photosensitizer 5,10,15,20-tetraphenylchlorin (TPC). In vitro experiments show that the prepared RBC(M(TPC-PTX)) is readily taken up into endosomes. Under appropriate light irradiation, the TPC can generate ROS, not only for PDT but also for triggering PTX₂-TK cleavage and on-demand PTX release for chemotherapy. In vivo results show that the coating of RBC membrane prolongs blood circulation and improves tumor accumulation. The combination of chemo- and photodynamic therapy enhances anticancer therapeutic activity, and light-triggered drug release reduces systematic toxicity. All these characteristics render the described technology extremely promising for cancer treatment.

Bi-phasic change in BDNF gene expression following antidepressant drug treatment

The gene for brain derived neurotrophic factor (BDNF) has recently received attention in relation to the therapeutic action of antidepressant treatment. This study aimed to clarify the influence of post drug interval on the effect of acute and repeated treatment with antidepressant drugs on BDNF gene expression in the rat brain. It was found that repeated administration of either the monoamine oxidase inhibitor tranylcypromine (TCP) or 5-hydroxytryptamine (5-HT) re-uptake inhibitors (fluoxetine, paroxetine and sertraline), evoke a bi-phasic and time-dependent effect on BDNF gene expression in the rat hippocampus (especially dentate gyrus). A down-regulation of the BDNF gene was detected at 4 h (TCP and fluoxetine) and an up-regulation at 24 h (TCP, paroxetine, fluoxetine, sertraline) after the last of twice daily injections for 14 days. After a single injection the down-regulation was detected at 4 h (TCP, fluoxetine, paroxetine and sertraline) but BDNF mRNA levels were not altered at 24 h post drug (TCP, fluoxetine and paroxetine). Administration of inhibitors of noradrenaline re-uptake (desipramine and maprotiline) or the atypical antidepressant mianserin had no effect on BDNF mRNA levels at either single (4 h post drug, desipramine) or repeated (24 h post drug, desipramine, maprotiline, mianserin) treatment. The gene expression for NT-3, which is distributed in a high density in the dentate gyrus, was not affected by single or repeated injections of antidepressant drugs (TCP, fluoxetine, paroxetine, sertraline, desipramine, maprotiline or mianserin) at 4 or 24 h post drug. In conclusion, these data show that the effect of antidepressant drugs on BDNF gene expression may be more complex and less widespread across treatments than previously thought. Thus, in this study drugs interacting with the central 5-HT system altered BDNF expression but the effect was bi-phasic over the 24 h post drug period.

Manipulations of brain 5-HT levels affect gene expression for BDNF in rat brain

The aim of the present study was to investigate whether changes in brain 5-HT concentrations affect the expression of BDNF mRNA in rat brain. Brain 5-HT concentration in the rat was elevated by combined treatment with tranylcypromine and L-tryptophan, tranylcypromine alone, by a single dose of the 5-HT releasing agent p-chloroamphetamine (PCA) or by the selective 5-HT reuptake inhibitor paroxetine. 5-HT was depleted by either multiple p-chlorophenylalanine (pCPA) or PCA injections. The extent of 5-HT depletion following pCPA or PCA was monitored using 5-HT immunocytochemistry. BDNF mRNA abundance in treated rats and the corresponding vehicle injected control rats was studied by in situ hybridization histochemistry (ISHH). Two hours after the combined administration of tranylcypromine and L-tryptophan BDNF mRNA abundance in the dentate gyrus was significantly decreased but increased in the frontal cortex. Tranylcypromine alone or a single injection of PCA had similar effects on BDNF mRNA expression to the combination of tranylcypromine and L-tryptophan, i.e. they caused significant reductions of BDNF mRNA expression in dentate gyrus and increased it in frontal cortex. Paroxetine also reduced BDNF mRNA in DG but was without effect in frontal cortex. Multiple injections of both pCPA or PCA resulted in marked reductions of 5-HT immunoreactive axons in the hippocampus, pCPA being more effective. Both drugs significantly increased BDNF mRNA abundances in the dentate gyrus. Multiple PCA injections also increased BDNF mRNA expression in parietal cortex, while pCPA induced 5-HT depletion was ineffective. These results suggests that 5-HT modulates BDNF mRNA levels in rat brain.

Engineering nanomedicines through boosting immunogenic cell death for improved cancer immunotherapy

Current cancer immunotherapy has limited response rates in a large variety of solid tumors partly due to the low immunogenicity of the tumor cells and the immunosuppressive tumor microenvironment (ITM). A number of clinical cancer treatment modalities, including radiotherapy, chemotherapy, photothermal and photodynamic therapy, have been shown to elicit immunogenicity by inducing immunogenic cell death (ICD). However, ICD-based immunotherapy is restricted by the ITM limiting its efficacy in eliciting a long-term antitumor immune response, and by severe systemic toxicity. To address these challenges, nanomedicine-based drug delivery strategies have been exploited for improving cancer immunotherapy by boosting ICD of the tumor cells. Nanosized drug delivery systems are promising for increasing drug accumulation at the tumor site and codelivering ICD inducers and immune inhibitors to simultaneously elicit the immune response and relieve the ITM. This review highlights the recent advances in nanomedicine-based immunotherapy utilizing ICD-based approaches. A perspective on the clinical translation of nanomedicine-based cancer immunotherapy is also provided.

Porphyrin-Based Carbon Dots for Photodynamic Therapy of Hepatoma

Porphyrin-containing carbon dots (CDs) possess ultrasmall size, excellent water solubility, and photostability. These CDs can effectively generate cytotoxic singlet oxygen upon irradiation, and induce the cell apoptosis. Photodynamic ability of CDs inhibits the growth of hepatoma. This work not only sheds light on developing functional carbon dots, but also highlights the importance of special-structure precursor molecules in synthesizing functional CDs.

A Paclitaxel Prodrug Activatable by Irradiation in a Hypoxic Microenvironment

The innate hypoxic microenvironment of most solid tumors has a major influence on tumor growth, invasiveness, and distant metastasis. Here, a hypoxia-activated self-immolative prodrug of paclitaxel (PTX₂ -Azo) was synthesized and encapsulated by a peptide copolymer decorated with the photosensitizer chlorin e6 (Ce6) to prepare light-boosted PTX nanoparticle (Ce6/PTX₂ -Azo NP). In this nanoparticle, PTX₂ -Azo prevents premature drug leakage and realizes specific release in hypoxic tumor microenvironment and the photosensitizer Ce6 not only efficiently generates singlet oxygen under light irradiation but also acts as a positive amplifier to promote the release of PTX. The combination of photodynamic therapy (PDT) and chemotherapy results in excellent antitumor efficacy, demonstrating the great potential for synergistic cancer therapy.

Tail pinch-induced changes in the turnover and release of dopamine and 5-hydroxytryptamine in different brain regions of the rat

Tail pinch was administered through a paper clip attached to the rat's tail. The ex vivo changes in the metabolite/transmitter ratio were used as a measure of changes in the turnover of dopamine and 5-hydroxytryptamine. After a 2-min tail pinch dopamine turnover was increased in the striatum but not in the frontal cortex, hypothalamus or olfactory tubercle; 5-hydroxytryptamine turnover was increased in frontal cortex and hippocampus and was unchanged in striatum, hypothalamus and olfactory tubercle. Microdialysis was used to monitor the changes in extracellular neurotransmitter and metabolite concentrations during and after tail pinch. A 5-min tail pinch caused a rapid rise of both dopamine in the striatum and 5-hydroxytryptamine in the hippocampus. There was a smaller increase in the 5-hydroxytryptamine metabolite 5-hydroxyindoleacetic acid and only a non-significant increase in the dopamine metabolite 3,4-dihydroxyphenylacetic acid.

Repeated electroconvulsive shock extends the duration of enhanced gene expression for BDNF in rat brain compared with a single administration

Brain-derived neurotrophic factor (BDNF) is known to modulate synaptic function as well as to promote neuronal growth in the adult brain. The aim of the present study was to compare the duration of electroconvulsive shock (ECS)-induced BDNF gene expression following a single shock (acute ECS) to the more clinically relevant situation, where repeated shocks (chronic ECS) are administered. For this purpose, we have used quantitative in situ hybridisation with a 35S-labelled oligonucleotide probe complementary to mRNAs encoding genes for all forms of BDNF. The results confirm previous studies that the administration of ECS increases BDNF mRNA abundance in parts of rat brain with particularly marked changes in the granule cell layer of the dentate gyrus. We also for the first time show the long lasting nature of the increase in BDNF mRNA abundance measured after chronic ECS, i.e., significant increases in BDNF mRNA persisted up to 48 h after the last shock. Acute ECS at 6 h after the shock produced a slightly more pronounced effect on BDNF mRNA abundance than chronic ECS 6 h after the last shock. However, this change was not detectable already 24 h after a single ECS. These results indicate that repeated ECS induces adaptive changes in BDNF mRNA expression.

Effect of antidepressant drugs on dopamine D1 and D2 receptor expression and dopamine release in the nucleus accumbens of the rat

This study examined the effect of repeated treatment with the antidepressant drugs, fluoxetine, desipramine and tranylcypromine, on dopamine receptor expression (mRNA and binding site density) in sub-regions of the nucleus accumbens and striatum of the rat. The effect of these treatments on extracellular levels of dopamine in the nucleus accumbens was also measured. Experiments using in situ hybridisation showed that the antidepressants caused a region-specific increase in D2 mRNA, this effect being most prominent in the nucleus accumbens shell. In contrast, none of the treatments increased D1 mRNA in any of the regions examined. Measurement of D2-like binding by receptor autoradiography, using the ligand [3H]YM-09151-2, revealed that both fluoxetine and desipramine increased D2-like binding in the nucleus accumbens shell; fluoxetine had a similar effect in the nucleus accumbens core. Tranylcypromine, however, had no effect on D2-like binding in the nucleus accumbens but decreased binding in the striatum. In micro-dialysis experiments, our data showed that levels of extracellular dopamine in the nucleus accumbens were not altered in rats treated with either fluoxetine or desipramine, but increased by tranylcypromine. From our findings, we propose that the antidepressant drugs tested enhance dopamine function in the nucleus accumbens through either increased expression of post-synaptic D2 receptors (fluoxetine and desipramine) or increased dopamine release (tranylcypromine).

Antidepressant drug treatment induces Arc gene expression in the rat brain

The mechanism underlying the therapeutic effect of antidepressants is not known but neuroadaptive processes akin to long-term potentiation have been postulated. Arc (Activity-regulated, cytoskeletal-associated protein) is an effector immediate early gene implicated in LTP and other forms of neuroplasticity. Recent data show that Arc expression is regulated by brain 5-hydroxytryptamine neurones, a target of many antidepressants. Here in situ hybridisation and immunohistochemistry were used to examine whether Arc expression in rat brain is altered by antidepressant drug treatment. Repeated administration of the monoamine reuptake inhibitors paroxetine, venlafaxine or desipramine induced region-specific increases in Arc mRNA. These increases were greatest in regions of the cortex (frontal and parietal cortex) and hippocampus (CA1 layer) and absent in the caudate putamen. Repeated treatment with the monoamine oxidase inhibitor, tranylcypromine, increased Arc mRNA in a similar fashion to the monoamine reuptake inhibitors. The antidepressant drugs also increased the number of Arc-immunoreactive cells in the parietal cortex. Acute antidepressant injection, and repeated administration of the antipsychotic drug chlorpromazine, produced either limited or no changes in Arc mRNA. The data suggest that chronic treatment with antidepressant drugs induces Arc gene expression in specific regions across the rat forebrain. Up-regulation of Arc expression may be part of the process by which antidepressant drugs achieve long-term changes in synaptic function in the brain.

Engineering Prodrug Nanomedicine for Cancer Immunotherapy

Immunotherapy has shifted the clinical paradigm of cancer management. However, despite promising initial progress, immunotherapeutic approaches to cancer still suffer from relatively low response rates and the possibility of severe side effects, likely due to the low inherent immunogenicity of tumor cells, the immunosuppressive tumor microenvironment, and significant inter- and intratumoral heterogeneity. Recently, nanoformulations of prodrugs have been explored as a means to enhance cancer immunotherapy by simultaneously eliciting antitumor immune responses and reversing local immunosuppression. Prodrug nanomedicines, which integrate engineering advances in chemistry, oncoimmunology, and material science, are rationally designed through chemically modifying small molecule drugs, peptides, or antibodies to yield increased bioavailability and spatiotemporal control of drug release and activation at the target sites. Such strategies can help reduce adverse effects and enable codelivery of multiple immune modulators to yield synergistic cancer immunotherapy. In this review article, recent advances and translational challenges facing prodrug nanomedicines for cancer immunotherapy are overviewed. Last, key considerations are outlined for future efforts to advance prodrug nanomedicines aimed to improve antitumor immune responses and combat immune tolerogenic microenvironments.

5-HT3 receptor antagonists inhibit morphine-induced stimulation of mesolimbic dopamine release and function in the rat

The effects of three different 5HT3 receptor antagonists, granisetron, ICS 205-930 and ondansetron (0.01, 0.1 and 1 mg/kg, s.c.) were tested on changes in mesolimbic dopamine function produced by 1 mg/kg of morphine in the rat. Increases of in vivo dopamine release and stimulation of behavioural activity (grooming, locomotion, rearing and sniffing) were monitored. Morphine (0.5 and 1 mg/kg, s.c.) increased dose-dependently the concentration of dopamine in dialysates obtained from the nucleus accumbens. This action of morphine was inhibited by the opiate antagonist naloxone (1 mg/kg, s.c.). Morphine (0.5 and 1 mg/kg) stimulated behavioural activity, which in the early part of the time course corresponded closely with the increase of dopamine in the nucleus accumbens. Pretreatment with 1 mg/kg (s.c.) of granisetron resulted in moderate inhibition (28%) of the morphine-induced stimulation of the extracellular dopamine levels, while doses of 0.01 and 0.1 mg/kg (s.c.) had no effect. The highest dose of granisetron (1 mg/kg, s.c.) also significantly reduced the morphine-induced enhancement of behavioural activity. The fact that granisetron attenuated morphine-induced effects on mesolimbic DA only at the highest dose tested (1 mg/kg, s.c.) was also true for ICS 205-930 and ondansetron. It is concluded that 5HT3 receptor antagonists partially inhibit, with low potency, the morphine-induced stimulation of dopamine release in the nucleus accumbens and the corresponding behavioural activation.

Serotonergic regulation of mRNA expression of Arc, an immediate early gene selectively localized at neuronal dendrites

Arc (activity regulated, cytoskeleton associated protein) is an effector immediate early gene that is selectively localized in the neuronal dendrites. Elevation of brain 5-HT by the combined administration of the monoamine oxidase inhibitor, tranylcypromine (TCP, 5 mg/kg, i.p.), and the 5-HT precursor L-tryptophan (L-TP, 100 mg/kg, i.p.), increased Arc mRNA abundance in the cingulate, orbital, frontal and parietal cortices as well as in the striatum but a reduction was observed in the CA1 region of the hippocampus. The 5-HT releasing agent p-chloroamphetamine (PCA, 5 mg/kg, s.c.) also increased Arc mRNA in the cortical and striatal areas. Depleting brain 5-HT with the tryptophan hydroxylase inhibitor, p-chlorophenylalanine (pCPA, 300 mg/kg, i.p. for two days), on the other hand, significantly attenuated the increase in Arc mRNA induced by tranylcypromine and L-tryptophan (TCP/L-TP). Pretreatment with the 5-HT2 receptor antagonist ketanserin (2 mg/kg, i.p.) significantly attenuated the effect of TCP/L-TP in the cortex but only partially in striatum and did not affect the reduction in the CA1 region. The 5-HT2 agonist DOI (0.2, 1 and 2 mg/kg, i.p.) dose-dependently increased Arc mRNA abundance in cortical areas with a pattern similar to that of TCP/L-TP and PCA. DOI, however, had much weaker effects on Arc mRNA in the striatum and did not have any significant effect in the CA1, CA3 and the dentate gyms (DG) of the hippocampus. Pretreatment with ketanserin completely blocked the effect of DOI on Arc expression. These data suggest that Arc mRNA expression can be induced in the cortex by increases in extracellular 5-HT and that 5-HT2 receptors play a major part in mediating such effects. Additional 5-HT receptors as well as other neurotransmitters may also be involved, particularly in the striatum and in CA1 subfield of the hippocampus. Overall, our data suggest that expression of Arc mRNA is highly responsive to changes in brain 5-HT functions, and may provide a sensitive marker of postsynaptic 5-HT2(2A and 2C) receptor functions.

Serotonergic cells of the rat raphe nuclei express mRNA of tyrosine kinase B (trkB), the high-affinity receptor for brain derived neurotrophic factor (BDNF)

Here we have studied the distribution of mRNA for tyrosine kinase B (trkB), the high-affinity receptor for brain-derived neurotrophic factor (BDNF) amongst serotonergic cell bodies of the raphe nuclei and their ascending projections into the dorsal hippocampus in the rat brain. Previous studies have shown that BDNF has got trophic action on serotonergic neurons. In the present study, we provide evidence that serotonergic neurons express mRNA for the functional receptor of BDNF, trkB. Intracerebro-ventricular (i.c.v.) injection of the 5-HT-specific neurotoxin, 5,7-dihydroxytryptamine, which lesions serotonergic cell bodies in the raphe nuclei as well as their ascending projections into the dorsal hippocampus, caused a dramatic loss of trkB mRNA from serotonergic cell bodies of the dorsal raphe nucleus. In contrast, there was no change in the abundance of trkB mRNA within the dorsal hippocampus. These findings provide direct evidence for the expression of trkB mRNA by serotonergic neurons and suggest distinct mechanisms of action of BDNF upon serotonergic neurons at the levels of their cell bodies and terminal projection sites.

In vivo neurochemical effects of tail pinch

Tail pinch in the rat gives rise to a well characterised pattern of behaviour which includes gnawing, licking and eating. We have used both in vivo voltammetry and microdialysis to monitor neurochemical changes which accompany the behavioural response to a 5-min tail pinch. Tail pinch resulted in a increase of extracellular 5-hydroxytryptamine and a smaller and more delayed increase of 5-hydroxyindole acetic acid in the hippocampus. In the striatum there was a rise of both extracellular dopamine and ascorbate. With a recently developed constant potential voltammetric technique we can continuously monitor changes in extracellular ascorbate. Using this technique we found a very rapid rise in ascorbate current during a 5-min tail pinch; the current began to decline as soon as the clip was removed. The high time resolution of the technique also allowed us to record similar ascorbate changes during a 0.5-s tail pinch.

Hybrid polymer micelles capable of cRGD targeting and pH-triggered surface charge conversion for tumor selective accumulation and promoted uptake

This study presents both tumor-targeting ligands (cRGD) and pH-activated surface charge-conversional moiety (imidazole) decorated micelles for Dox delivery. cRGD is expected to induce preferential tumor accumulation, while imidazole switches on positive charge in a tumor acid environment, which leads to enhanced micelle uptake by tumor cells.

Both systemic and local administration of benzodiazepine agonists inhibit the in vivo release of 5-HT from ventral hippocampus

The effects of benzodiazepine- and GABAA-receptor agonists and antagonists on the release and metabolism of 5-HT were measured in the ventral hippocampus of freely moving rats using microdialysis. Systemic injections of the benzodiazepine agonists, flurazepam and diazepam reduced the levels of 5-HT while the partial inverse agonist, FG 7142 (N-methyl-beta-carboline-3-carboxamide), had no effect. Local perfusion of flurazepam through the dialysis probe also decreased the release of 5-HT in the ventral hippocampus, an effect which was completely blocked by the benzodiazepine antagonist, Ro15-1788 (flumazenil). Local application of the GABAA agonist muscimol had no effect on the release of 5-HT, while the antagonist picrotoxin, administered locally, caused a 4-fold enhancement of release of 5-HT. Picrotoxin also resulted in a complete block of the inhibitory effect of flurazepam on release of 5-HT. None of these drugs caused significant changes in the levels of the metabolite of 5-HT, 5-hydroxyindoleacetic acid (5-HIAA) in the ventral hippocampus. These results suggest that the inhibitory effect of flurazepam on the release of 5-HT is mediated by benzodiazepine/GABAA receptors in the hippocampus and that GABA exerts a tonic inhibitory effect on the release of 5-HT in the region of the brain.

Glutamate receptor activation is involved in 5-HT2 agonist-induced Arc gene expression in the rat cortex

Brain 5-HT regulates the expression of gene transcription factor as well as novel effector immediate early genes (IEGs). The 5-HT regulation of the gene transcription factor IEG, c-fos, involves activation of 5-HT2A and ionotropic glutamate receptors. Here, we investigate whether these receptors are also involved in the regulation of the effector IEG, Arc. In rats, the 5-HT2 agonist DOI induced a marked increase in expression of Arc mRNA in a variety of cortical regions. This effect was blocked by the selective 5-HT2A receptor antagonist, MDL 100,907, but not the 5-HT(2B/2C) receptor antagonist, SB206553. The AMPA receptor antagonist GYKI 52466 also attenuated DOI-induced Arc mRNA expression, as did the NMDA receptor antagonist MK801 in some regions. Immunofluorescence studies showed that DOI increased Arc-immunoreactivity in cortical cells that expressed AMPA and NMDA receptor subunits but not the 5-HT2A receptor. Finally, DOI-induced Arc-immunoreactivity in cortical cells was extensively co-localised with c-fos-immunoreactivity. These results suggest that, as with c-fos expression, ionotropic glutamate receptors (AMPA and NMDA) are involved in 5-HT2A receptor-induced Arc expression. This finding, together with evidence of extensive Arc and c-fos co-localisation, suggests that 5-HT2A receptor activation may induce the expression of both effector and transcription factor IEGs via common molecular and cellular substrates.