Low Initial Release Research Articles

Influence of Activation Parameters on the Mechanical and Microstructure Properties of an Alkali-Activated BOF Steel Slag

Steel slag (SS) is a secondary material from steelmaking production with little commercial value. Its volumetric expansion and low reactivity limit the use of SS in Portland cement (PC)-based materials. This study investigated the potential use of basic oxygen furnace (BOF) slag as a single precursor in alkali-activated matrices (AAMs). Six AAM pastes were assessed by changing the silica modulus (0.75, 1.50 and 2.22) and the sodium concentration (4% or 6% Na2O—wt. SS). The early hydration was assessed using isothermal calorimetry (IC), followed by the assessment of the mechanical performance (compressive strength), apparent porosity, and structure and microstructure characterization (X-ray diffraction, thermogravimetric analysis and scanning electron microscopy). The results indicated that although the BOF slag may be considered a low-reactivity material, the alkaline environment effectively dissolved important crystalline phases to produce hydrates (reaction products). An optimized combination of activator sources was achieved with 4% Na2O and a silica modulus of 1.50–2.22, with a compressive strength up to 20 MPa, a significant amount of reaction products (C-S-H/C-A-S-H gels), and low initial and cumulative heat release. Those properties will help to promote SS recycling use in future engineering projects that do not require high-strength materials.

Effects of Surfactants on Zein Cast Films for Simultaneous Delivery of Two Hydrophilic Active Components.

In order to prepare edible films with outstanding antimicrobials and antioxidants utilized in applications of food and pharmaceutics, in this study, effects of surfactants on zein cast films for simultaneous delivery of lysozyme (LY) and ascorbic acid (AA) were investigated, where sodium alginate (SA), soy lecithin (SL), and Pluronic f-68 (PF-68) were selected as surfactants. FT-IR tests indicated that SL or PF-68 dramatically changed secondary structure of zein composite films, which heightened the irregularity of the composite film and inhibited LY crystallization. Mechanical tests showed that highly flexible films exhibiting elongations between 129% and 157% were obtained when adding PF-68. Compared with the film without emulsifier, zein film containing SL and PF-68 showed approximately 7.51 and 0.55 times lower initial release rates for LY and AA respectively, which significantly improved the controlled release and heightened the anti-microbial and anti-oxidant activities of the film. Finally, emulsified mechanisms of the surfactants in zein films were proposed.

In situ preparation of Pd nanoparticles on N-doped graphitized carbon derived from ZIF-67 by nitrogen glow-discharge plasma for the catalytic dehydrogenation of dodecahydro-N-ethylcarbazole

To date, liquid organic hydrogen carrier technology has been generally considered to be one of the most promising solutions for the storage and transportation of hydrogen. Addressing several issues, including high hydrogen release temperature and low initial release rate, is key to this technology. Pd catalysts (Pd/NpGC) supported on porous N-doped partially graphitized ZIF-67-derived carbon (NpGC) were prepared in situ using nitrogen glow discharge plasma. The structure, composition, and morphology of the prepared catalysts were characterized by XRD, Raman spectroscopy, TEM, XPS, and N2 adsorption–desorption. During the calcination of ZIF-67, porous N-doped carbon was formed and partially graphitized under the influence of Co. The Pd nanoparticles (Pd NPs) of the Pd/NpGC catalysts had an average size of 3.2 nm with higher dispersion and a higher fraction of Pd (111) facets. In the process of Pd2+ reduction, NpGC was doped twice with N simultaneously. The synergy between highly active Pd NPs and N-doped partially graphitized carriers (NpGC) reduced the electronic binding energy of Pd and improved the catalytic performance of Pd/NpGC for hydrogen production from dodecahydro-N-ethylcarbazole (H12-NEC). The results showed that the amount of hydrogen released in the dehydrogenation reaction at 180℃ was 4.06 wt% after 1 h and 5.76 wt%, after 10 h. The H12-NEC conversion rate was 100%, the selectivity of N-ethylcarbazole (NEC) was 98.72%, and the final dehydrogenation reached 99.20%.

Electrospun Nanofibers for Dual and Local Delivery of Neuroprotective Drugs

Drug delivery for neuroprotection/neuroregeneration after traumatic peripheral nerve injuries still remains a challenge. For this purpose, we formulated composite nanofiber formulation for the dual local delivery of alpha lipoic acid (ALA) and atorvastatin (ATR) to enhance regeneration process after peripheral nerve injury. The initial stage involved encapsulation of ATR into nanosprayed chitosan (CH) nanoparticles after which the CH nanoparticles were embedded into poly(lactic-co-glycolic acid) (PLGA) nanofibers containing freely dispersed ALA within the fiber structure. Morphology investigations revealed that smooth and randomly aligned nanofibers with mean diameter of 340±69 nm were formed. Encapsulation efficiency for ALA and ATR were calculated as 92.76±3.53 % and 89.27±5.053 %, respectively. Differential Scanning Calorimetry and FT-IR analysis confirmed successful encapsulation of ALA and ATR into the composite nanofibers; however, XRD results indicated surface localization of ALA within the structure. Porosity and pore volume of the nanofibers increased in accordance with increase in density of the electrospunned solution. Similarly, mechanical strength of the nanofibers was found to increase significantly following the incorporation of ALA and ATR with respect to the unloaded nanofibers (p<0.05). Dual release of ALA and ATR in different fashions was confirmed by in-vitro release test of the nanofibers. For ALA, an immediate release percentage of 83.90 % within the first hour was observed. On the other hand, ATR exhibited a three-stage release profile which begins with a relatively lower initial release (22.07 %) in comparison to ALA followed by an increasing release (82.439%) up to 150 h. According to cell viability results, blank and loaded formulations were found to have no cytotoxic effect on both L-929 and B35 cell lines after incubation for up to 48 h. Based on this, composite PLGA nanofibers could be classified as suitable candidates for long-term and local delivery of neuroprotective drugs in peripheral nerve injury.

Preparation of non-spherical vaterite CaCO3 particles by flash nano precipitation technique for targeted and extended drug delivery

An ideal anticancer drug release system is designed to release drugs over a prolonged period while minimizing the initial burst to significantly reduce the side effects and the number of medications. In this study, CaCO3 particles (average diameter 800-1600 nm with PDI < 0.2) aiming at such controlled release system were successfully prepared via Flash Nano Precipitation technique. Hydroxypropyl methylcellulose and sodium dodecyl sulfate were both employed as additives for CaCO3 crystallization to promote the formation of vaterite and convex-disc-shaped CaCO3, and at the same time as stabilizers for CaCO3 particles to control particle growth and avoid particle agglomeration. By using the as-prepared vaterites, a satisfying drug loading capacity (~0.1 mg drug/mg particle) was realized, and prolonged drug release was achieved with a low initial release (< 10% within 1 day at pH = 6.0) and approximately zero-order release kinetics before 36 h (R2 > 0.97) or after 36 h (R2 > 0.99). Besides, by changing the particle size, different drug release kinetics could be achieved while the high drug loading capacity and low initial release were both maintained. The vaterite particles prepared in this work could be a potential candidate drug carrier for extended drug release with minimized initial burst and a constant drug releasing rate.

Microemulsions based on polyglycerol polyricinoleate as drug delivery systems

The aim of the work is to develop composition of reverse microemulsion stabilized by the surfactant from a number of polyglycerol polyricinoleates for encapsulating water-soluble biologically active substance (BAS) and studying the kinetics of its release into the medium simulating the medium of the small intestine. Materials and methods. Possible stable (equilibrium) phases of the reverse microemulsion in the pseudoternary system water–PG-3-PR/Tween 80–paraffin oil were determined by titration of surfactant/co-surfactant mixtures–oil in water with hydrophilic-lipophilic balance (HLB) values of the surfactant mixture ranging from 4.0 to 7.0. Stability of a number of compositions during storage at 20 °C for 6 months was studied. Based on the obtained data, a composition was selected for encapsulating methylene blue (MS) dye as a model of a water-soluble biologically active substance. Microemulsion was obtained by mixing paraffin oil and surfactants with selected mass ratio followed by the addition of an aqueous phase. Reverse microemulsion morphology was evaluated with transmission electron microscopy (TEM). To evaluate the in vitro drug release rate, aliquots of an aqueous dye solution (control sample) and MB-containing microemulsions were placed in dialysis bags and immersed in 0.01 M phosphate-buffered saline (PBS) (pH 7.4) in a thermostatic shaking incubator at 180 rpm and 37 °C. Aliquots of the release medium were selected at predetermined time intervals and the concentration of MB dye was determined using a UV spectrophotometer at 660 nm. Results. Composition containing 13.5 wt% paraffin oil, 76.5 wt% mixture of PG3-PR/Tween 80 (HLB 5.5) and 10 wt% water was chosen to encapsulate the biologically active agents. Number average droplet diameter in the dispersed phase of the obtained microemulsion was 55 nm. Dye-loaded microemulsion sample showed a prolonged release of biologically active substances within 48 hours of the experiment (15.2%) and low initial release rate. Conclusion. Possible stable phases of reverse microemulsion in the pseudoternary system water–PG-3-PR/Twin 80–paraffin oil were determined in the course of the work and optimal microemulsion composition for encapsulating medicinal substances was found. It was shown that the resulting microemulsion system provides a sustained release of methylene blue as a model of a water-soluble biologically active substance in a medium simulating medium of the small intestine. The obtained data allow to consider this composition as a potential nanoscale system for the sustained delivery of water-soluble drugs.

Bioactive ophiopogonin release form bioglass-collagen-phosphatidylserine scaffolds to enhance bone repair in vitro

The goal of this study is to construct bone scaffolds with neuroregulatory function. The scaffolds were prepared using bioglass (BG) powder, collagen (COL) solution, phosphatidylserine (PS) and ophiopogonin loaded COL microspheres as the main components. Combinatorial processing techniques involving chemical-crosslinking and freeze-drying were used. The resultant scaffold constructs were characterized in terms of their morphology, drug release kinetics, pharmacological and biological activities for osteoblast and neurocyte. The microporphology observation showed that the scaffolds had highly interconnected pores, favorable drug release kinetics in view of low initial release and slow average release rate. Moreover, cell studies showed that the involvement of ophiopogonin contributed to the proliferation and mineralization of MC3T3-E1 cells, and the neurite outgrowth of neuron. The drug-loaded composite scaffolds may therefore be a potential replacement in bone-tissue engineering.

Elfn1-Induced Constitutive Activation of mGluR7 Determines Frequency-Dependent Recruitment of Somatostatin Interneurons.

Excitatory synapses onto somatostatin (SOM) interneurons show robust short-term facilitation. This hallmark feature of SOM interneurons arises from a low initial release probability that regulates the recruitment of interneurons in response to trains of action potentials. Previous work has shown that Elfn1 (extracellular leucine rich repeat and fibronectin Type III domain containing 1) is necessary to generate facilitating synapses onto SOM neurons by recruitment of two separate presynaptic components: mGluR7 (metabotropic glutamate receptor 7) and GluK2-KARs (kainate receptors containing glutamate receptor, ionotropic, kainate 2). Here, we identify how a transsynaptic interaction between Elfn1 and mGluR7 constitutively reduces initial release probability onto mouse cortical SOM neurons. Elfn1 produces glutamate-independent activation of mGluR7 via presynaptic clustering, resulting in a divergence from the canonical "autoreceptor" role of Type III mGluRs, and substantially altering synaptic pharmacology. This structurally induced determination of initial release probability is present at both layer 2/3 and layer 5 synapses. In layer 2/3 SOM neurons, synaptic facilitation in response to spike trains is also dependent on presynaptic GluK2-KARs. In contrast, layer 5 SOM neurons do not exhibit presynaptic GluK2-KAR activity at baseline and show reduced facilitation. GluK2-KAR engagement at synapses onto layer 5 SOM neurons can be induced by calmodulin activation, suggesting that synaptic function can be dynamically regulated. Thus, synaptic facilitation onto SOM interneurons is mediated both by constitutive mGluR7 recruitment by Elfn1 and regulated GluK2-KAR recruitment, which determines the extent of interneuron recruitment in different cortical layers.SIGNIFICANCE STATEMENT This study identifies a novel mechanism for generating constitutive GPCR activity through a transsynaptic Elfn1/mGluR7 structural interaction. The resulting tonic suppression of synaptic release probability deviates from canonical autoreceptor function. Constitutive suppression delays the activation of somatostatin interneurons in circuits, necessitating high-frequency activity for somatostatin interneuron recruitment. Furthermore, variations in the synaptic proteome generate layer-specific differences in facilitation at pyr → SOM synapses. The presence of GluK2 kainate receptors in L2/3 enhances synaptic transmission during prolonged activity. Thus, layer-specific synaptic properties onto somatostatin interneurons are mediated by both constitutive mGluR7 recruitment and regulated GluK2 kainate receptor recruitment, revealing a mechanism that generates diversity in physiological responses of interneurons.

Inoculative release strategies of Macrolophus pygmaeus Rambur (Hemiptera: Miridae) in tomato crops: population dynamics and dispersal

Macrolophus pygmaeus Rambur (Hemiptera: Miridae) is a key biological control agent in greenhouse tomato crops. In the present study, we describe the population dynamics of M. pygmaeus after release during two generations in semi-commercial greenhouses in order to optimize biocontrol programs. We tested the effect of the number of weekly supplementary food applications consisting of a mixture of Ephestia kuehniella Zeller and Artemia franciscana Kellogg in a tomato crop on population numbers of M. pygmaeus at low and high initial release densities of the predator. Also, the effect of supplementary feeding on the predator’s dispersal was studied. Larger population densities of M. pygmaeus were obtained when food was supplied for a longer period. However, we observed fruit damage by M. pygmaeus at high densities resulting from too frequent food applications. Also, dispersal was slowed down as the number of supplementary food applications increased. Distributing M. pygmaeus over more plants at release results in higher total population densities. The optimal inoculative release strategy of M. pygmaeus is a trade-off between high population densities and fruit damage, fast or slow dispersal throughout the greenhouse and the number of release plants and work/costs related to the supplementation of food. The optimal strategy to overcome negative effects like fruit damage, slow dispersal and potential cannibalism proved to be a weekly provision of supplementary food during 6–8 weeks, with an initial release density strategy of 20 M. pygmaeus adults per plant. These results contribute to a more sustainable tomato production. A reliable and efficient inoculative release strategy for the key predator M. pygmaeus enhances the biocontrol potential and is of great value for tomato growers.

Fabrication of Multiple Layered Scaffolds with Controlled Porous Micro-Architecture

A multi-layer scaffold that incorporates bioglass, phosphatidylserine and steroidal saponins loaded collagen microparticles was prepared in this study. Combinatorial processing techniques involving porogen leaching protocol and freeze-drying were used. Drug distribution and microstructure could be controlled mainly by the concentrations of drug-loaded collagen microparticles and porogen as well as freezing temperature for different layers of the scaffolds. Morphological observation, measurement of swelling properties, examination of drug release kinetics, and analysis of cell bioactivity showed that the resultant scaffolds had highly interconnected pores, gradient drug distribution and graded porous micro-architecture, similar swelling ratio for different layers, better drug release kinetics in view of lower initial release and slower average release rate compared to the scaffolds with homogeneous structure, as well as approving support of cell ingrowth. This study suggests that the optimized scaffolds have promising potential for applications in bone tissue engineering.

Controlled-release drug carriers based mesoporous silica spheres with hierarchical hollow/nano structure

Mesoporous silica spheres with hierarchical hollow/nano structure (MSSH-H/N) have been successfully prepared by a template-guided approach, in which cetyltrimethyl ammonium bromide (CTAB) and polystyrene (PS) emulsion was used as the template of mesopores and hollow core, respectively. A consecutive template mechanism and the formation of the hierarchical hollow/nano structure were proposed on basis of the combined characterizations including transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction patterns (XRD) and nitrogen sorption analysis, which showed that the hierarchical structure is composed of mesoporous hollow SiO2 spheres and discrete mesoporous SiO2 nanoparticles coating on the shell. Ibuprofen (IBU) was chosen as a drug model in delivery and release experiments, and these MSSH-H/N samples exhibited higher drug loading capacity, desired low initial IBU release rate and typical two-phase drug release behavior compared with conventional single-structure (single-shelled) hollow mesoporous silica spheres due to their unique hierarchical hollow/nano structure.

The calcium sensor synaptotagmin 7 is required for synaptic facilitation.

It has been known for over 70 years that synaptic strength is dynamically regulated in a use-dependent manner1. At synapses with a low initial release probability, closely spaced presynaptic action potentials can result in facilitation, a short-term form of enhancement where each subsequent action potential evokes greater neurotransmitter release2. Facilitation can enhance neurotransmitter release manyfold and profoundly influence information transfer across synapses3, but the underlying mechanism remains a mystery. Among the proposed mechanisms is that a specialized calcium sensor for facilitation transiently increases the probability of release2,4 and is distinct from the fast sensors that mediate rapid neurotransmitter release. Yet such a sensor has never been identified, and its very existence has been disputed5,6. Here we show that synaptotagmin 7 (syt7) is a calcium sensor that is required for facilitation at multiple central synapses. In syt7 knockout mice, facilitation is eliminated even though the initial probability of release and presynaptic residual calcium signals are unaltered. Expression of wild-type syt7 in presynaptic neurons restored facilitation, whereas expression of a mutated syt7 with a calcium-insensitive C2A domain did not. By revealing the role of syt7 in synaptic facilitation, these results resolve a longstanding debate about a widespread form of short-term plasticity, and will enable future studies that may lead to a deeper understanding of the functional importance of facilitation.

Reliability and Precision Are Optimal for Non-Uniform Distributions of Presynaptic Release Probability

Most conceptual and computational models assume that synaptic transmission is reliable, a simplification rarely substantiated by data. The functional consequences of the recruitment of high and low initial release probability synapses on the reliability and precision of their postsynaptic targets are studied in a multi-compartmental model of a hippocampal CA1 pyramidal cell. We show that changes in the firing rate of CA3 afferent inputs (rate remapping) are not reflected in the firing rate of the CA1 cell but in the reliability and precise timing of some of its action potentials, suggesting that a signature of remapping may be found in the precise spike timing of CA1. Our results suggest that about half of the action potentials produced by a CA1 cell can potentially carry reliable information in their precise timing with about 25 ms precision, a time scale on the order of the gamma cycle. We show further that reliable events were primarily elicited by CA3 synapses in a state of low probability of release. Overall, our results suggest that the non-uniform distribution of initial release probabilities observed experimentally achieves an optimum yielding simultaneously high precision and high reliability, and allows large populations of CA3 synapses to contribute to the production of reliable CA1 spiking events.

Uniform-sized water-in-oil vaccine formulations enhance immune response against Newcastle disease and avian influenza in chickens.

Water-in-oil (W/O) emulsion is one of the best "one-shot" delivery system for antigen to generate high and durable antibody response. Here a facile method using premixed Shirasu Porous Glass (SPG) membrane emulsification technique was employed to fabricate uniform-sized emulsion and mechanical stirring was employed to prepare non-uniform-sized emulsion as control. In release kinetics studies, uniform-sized emulsion showed low initial release, and during the followed 17 days, uniform-sized emulsions released antigen faster than emulsions of non-uniform size. In addition, vaccination studies against Newcastle disease virus (NDV) and avian Influenza virus (AIV) demonstrated that emulsion of uniform size induced higher HI antibodies and antigen-specific IgG titers. Furthermore, chickens vaccinated with emulsion of uniform size had a significantly greater ratio of CD8+ T cells to CD4+ T cells and a higher percentage of CD8+CD4+ T cells. Taken together, these results indicated that emulsion of uniform size induced a more potent immune response than emulsion prepared by mechanical stirring, and warranted the use of SPG membrane emulsification technique in generating new avian vaccines.

Relative influences of plant type and parasitoid initial density on host–parasitoid relationships in a tritrophic system

To explore the effects of bottom-up and top-down forces on the relationships between a host, Plutella xylostella (L.) (Lepidoptera, Plutellidae), and its parasitoid, Cotesia vestalis (Haliday) (Hymenoptera, Braconidae), a short-term field experiment was established as a factorial experiment using three different host plants (Brassica pekinensis cv. Yuki F1, Brassica oleracea var. capitata cv. Midorimaru F1 and B. oleracea var. botrytis cv. Snow Crown) in the presence of C. vestalis at two different levels (low and high initial release). The tritrophic interactions were monitored by census counts of live adults 20 days after parasitoid release. The mean numbers of P. xylostella and C. vestalis adults were compared using log-linear analysis of deviance. Also, differences in the levels of parasitism were analysed using logistic analysis of deviance. There was a significant effect of host plant type on the abundance of P. xylostella, the abundance of C. vestalis and the percentage parasitism of P. xylostella by C. vestalis. The mean number of P. xylostella adults per cage on common cabbage or cauliflower was significantly greater than that on Chinese cabbage. The mean number of C. vestalis adults and the proportion of hosts attacked by C. vestalis per cage were significantly greater on Chinese cabbage compared with common cabbage or cauliflower. Indeed, initial parasitoid release did not significantly affect the abundance of P. xylostella but there was a significant influence of initial parasitoid release on the abundance of C. vestalis and the levels of parasitism of P. xylostella by C. vestalis. The mean number of C. vestalis adults and the proportion of P. xylostella parasitised by C. vestalis per cage were greater in high level of parasitoid release compared with low level of parasitoid release. However, there were no significant interacting effect of the factors (plant type × parasitoid initial abundance) on the abundance of P. xylostella, the population size of C. vestalis and parasitism of P. xylostella by C. vestalis.

High Frequency Burst Firing of Granule Cells Ensures Transmission at the Parallel Fiber to Purkinje Cell Synapse at the Cost of Temporal Coding

Cerebellar granule cells (GrCs) convey information from mossy fibers (MFs) to Purkinje cells (PCs) via their parallel fibers (PFs). MF to GrC signaling allows transmission of frequencies up to 1 kHz and GrCs themselves can also fire bursts of action potentials with instantaneous frequencies up to 1 kHz. So far, in the scientific literature no evidence has been shown that these high-frequency bursts also exist in awake, behaving animals. More so, it remains to be shown whether such high-frequency bursts can transmit temporally coded information from MFs to PCs and/or whether these patterns of activity contribute to the spatiotemporal filtering properties of the GrC layer. Here, we show that, upon sensory stimulation in both un-anesthetized rabbits and mice, GrCs can show bursts that consist of tens of spikes at instantaneous frequencies over 800 Hz. In vitro recordings from individual GrC-PC pairs following high-frequency stimulation revealed an overall low initial release probability of ~0.17. Nevertheless, high-frequency burst activity induced a short-lived facilitation to ensure signaling within the first few spikes, which was rapidly followed by a reduction in transmitter release. The facilitation rate among individual GrC-PC pairs was heterogeneously distributed and could be classified as either “reluctant” or “responsive” according to their release characteristics. Despite the variety of efficacy at individual connections, grouped activity in GrCs resulted in a linear relationship between PC response and PF burst duration at frequencies up to 300 Hz allowing rate coding to persist at the network level. Together, these findings support the hypothesis that the cerebellar granular layer acts as a spatiotemporal filter between MF input and PC output (D’Angelo and De Zeeuw, 2009).

Preparation of sustained release rifampicin microparticles for inhalation

The aim of this research was to develop a novel carrier-free dry powder formulation of rifampicin for inhalation with controlled-release properties. Rifampicin dihydrate (RFDH) microcrystals were prepared by a polymorphic transformation of rifampicin. The prepared RFDH microcrystals were coated with poly (DL-lactide-co-glycolide) or poly (DL-lactide), using a spray-dryer equipped with two different types of three-fluid (3F) spray nozzles. The physicochemical and aerodynamic properties of the coated RFDH microcrystals were compared with those of conventional matrix microparticles. The coated RFDH powder, encapsulating 50% of rifampicin, was successfully prepared by simple in-situ coating methods using two different types of 3F nozzles and had mass median aerodynamic diameter values of 3.5-4.5 µM. The thin flaky morphology of RFDH powders, providing good aerosolization properties, was maintained after coating. The coated RFDH formulations showed relatively low initial rifampicin release, compared with the uncoated RFDH crystals, followed by slow rifampicin release (about 70%) over 8 h in phosphate-buffered saline media (pH 7.4). Significant chemical degradations were not observed from the crystalline-structured RFDH formulations, while the amorphous-structured matrix formulations showed chemical degradation in six months. These polymer coated RFDH formulations may be a valuable alternative in the treatment of tuberculosis since the carrier-free formulation offers the benefit of delivering a maximum-potency formulation of the antibiotic directly to the site of infection, and long drug residence times may be achieved by the controlled release of the drug.

Development of a spray-drying method for the formulation of respirable microparticles containing ofloxacin–palladium complex

The purpose of this study was to produce low-releasing spray-dried polymeric microparticles (MP) useful to target alveolar macrophages in tuberculosis (TB) inhalation therapy. Ofloxacin (Ofx) was encapsulated as ofloxacin-palladium (Ofx-Pd) complex into poly DL-lactide (PLA) MP by spray-drying. Ofx-Pd was prepared according to a method previously reported. A D-optimal design was employed to optimize drug content (DC), aerodynamic diameter (d(ae)) and span. d(ae) was calculated coupling tap-density to particle size analysis. The MP were characterized by SEM, UV spectrophotometry, and DSC. In vitro drug release was performed in comparison to Ofx loaded PLA MP. The Ofx-Pd complex formed spontaneously with a 1:1 stoichiometry. Inlet temperature, drug loading and polymer concentration resulted the most influential. Optimal MP had span of 0.9, a round shape, d(ae) of 2.5 μm, and DC of 30% (w/w). DSC and SEM analyses correlated with particle size. The optimized MP formulation showed a very low release at pH 7.4 compared to spray-dried Ofx loaded MP, the release increased slightly at lower pHs. Potentially inhalable MP were obtained by an optimized spray-drying process. The very low initial drug release at physiologic pH could be useful to target alveolar macrophages and to avoid systemic exposure.

Estradiol Acutely Potentiates Hippocampal Excitatory Synaptic Transmission through a Presynaptic Mechanism

Although recent evidence suggests that the hippocampus is a source of 17β-estradiol (E2), the physiological role of this neurosteroid E2, as distinct from ovarian E2, is unknown. One likely function of neurosteroid E2 is to acutely potentiate excitatory synaptic transmission, but the mechanism of this effect is not well understood. Using whole-cell voltage-clamp recording of synaptically evoked EPSCs in adult rat hippocampal slices, we show that, in contrast to the conclusions of previous studies, E2 potentiates excitatory transmission through a presynaptic mechanism. We find that E2 acutely potentiates EPSCs by increasing the probability of glutamate release specifically at inputs with low initial release probability. This effect is mediated by estrogen receptor β (ERβ) acting as a monomer, whereas ERα is not required. We further show that the E2-induced increase in glutamate release is attributable primarily to increased individual vesicle release probability and is associated with higher average cleft glutamate concentration. These two findings together argue strongly that E2 promotes multivesicular release, which has not been shown before in the adult hippocampus. The rapid time course of acute EPSC potentiation and its concentration dependence suggest that locally synthesized neurosteroid E2 may activate this effect in vivo.

In vitro and in vivo study of thymosin alpha1 biodegradable in situ forming poly(lactide-co-glycolide) implants

The purpose of this study was to develop poly(lactide-co-glycolide) (PLGA) based in situ forming implants (ISFI) for controlled release of thymosin alpha 1 (Tα1). The ISFI was prepared by dissolving PLGA in N-methyl-2-pyrrolidone (NMP) or mixtures of NMP and triacetin. Tα1 microparticles, prepared by spray-freeze drying method with chitosan or bovine serum albumin as a protectant, were suspended in PLGA solutions. The effects of Tα1 pre-encapsulation, PLGA molecular weight, PLGA concentration and organic solvents composition on the in vivo Tα1 release were evaluated by subcutaneously injecting Tα1-loaded ISFI into Sprague–Dawley Rats. The pharmacological efficacy of Tα1-loaded ISFI was examined using immunosuppressive BALB/c mice induced by cyclophosphamide. The ISFI composed of Tα1 pre-encapsulated with chitosan, higher molecule-weight PLGA at higher concentration and more triacetin showed a lower initial release and a longer sustained release period. The optimal prescription of our study showed a low initial release of 29.3% (24 h), followed by a slow and continuous drug release up to 28 d in vivo. An in vitro release device was designed to mimic the in vivo release of Tα1, and good correlation was observed between the in vitro and in vivo releases, with the linear correlation coefficient of 0.9899. Tα1-loaded ISFI showed low cytotoxicity as tested by CCK-8 assay. Tα1-loaded ISFI significantly increased the thymic index and spleen index of immunosuppressive mice. These results suggest that the ISFI is a suitable system for controlled release of Tα1.