Sustained-Release Triamcinolone Acetonide Hydrogels Reduce Hearing Threshold Shifts in a Model for Cochlear Implantation with Hearing Preservation.

INTRODUCTION: In recent years, the preservation of residual hearing has become a major factor in patients undergoing cochlear implantation (CI). In studies attempting to pharmaceutically improve hearing preservation rates, glucocorticoids (GCs) applied perioperatively in many institutions have emerged as a promising treatment regimen. Although dexamethasone is most commonly used and has been applied successfully by various research groups, recently pharmacological properties have been reported to be relatively unsuitable for topical delivery to the inner ear. Consequently other glucocorticoids merit further evaluation. The aim of this study was therefore to evaluate the otoprotective effects of the topical application of a sustained-release triamcinolone acetonide (TAAC) hydrogel in CI with hearing preservation. METHODS: Normal-hearing pigmented guinea pigs were randomized into a group receiving a single dose of a 6% TAAC poloxamer 407 hydrogel, a group receiving a 30% TAAC hydrogel and a control group. All hydrogel applications were performed 1 day prior to CI. After a cochleostomy was drilled, a specifically designed silicone electrode was inserted into the scala tympani for 5 mm. Frequency-specific compound action potentials of the auditory nerve (0.5-32 kHz) were measured pre- and directly postoperatively as well as on days 3, 7, 14, 21, and 28. Finally, temporal bones were harvested for histological evaluation. RESULTS: Application of the TAAC hydrogels resulted in significantly reduced hearing threshold shifts in low, middle and high frequencies and improved spiral ganglion cell survival in the second turn of the cochlea. Outer hair cell numbers in the basal and second turn of the cochlea were slightly reduced after TAAC application. CONCLUSION: In summary, we were able to demonstrate functional benefits of a single preoperative application of a TAAC hydrogel in a guinea pig model for CI, which persisted until the end of the observational period, that is, 28 days after surgery.

Evaluation of Sustained-Release Steroid Hydrogels in a Guinea Pig Model for Noise-Induced Hearing Loss.

The otoprotective effects of thermoreversible poloxamer 407 hydrogels containing dexamethasone or triamcinolone acetonide were evaluated in an animal model of noise-induced hearing loss. Seven days after noise exposure, hearing threshold shifts at 16 kHz were significantly reduced in the 6% dexamethasone group (p < 0.05). Even though no significant differences in hair cell counts were found, histological analysis revealed a significantly higher spiral ganglion cell density in the first turn of the cochlea in this group (p < 0.05). No otoprotective effects were observed after the application of the triamcinolone acetonide hydrogels. As the findings of this study indicate potential otoprotective effects of sustained topical dexamethasone delivery in the setting of noise-induced hearing loss, this strategy merits further evaluation.

Noise trauma and systemic application of the selective glucocorticoid receptor modulator compound A.

BACKGROUND: Selective glucocorticoid receptor modulators (SEGRMs) comprise a novel class of drugs promising both reduced side effects and similar pharmacological potency relative to glucocorticoids, which presently serve as the only clinical treatment for many otologic disorders. In the first otologic SEGRM experiment in an animal model of noise trauma, we compare the effects of Compound A (a SEGRM) and dexamethasone (potent glucocorticoid). METHODS: Forty adult guinea pigs received experimental treatment once daily for ten days. The animals were divided into four cohorts based on the treatment received: Compound A (1 mg/kg or 3 mg/kg), dexamethasone (1 mg/kg) as gold standard, or water as negative control. After five applications, animals were exposed to broadband noise (8-16 kHz) at 115 dB for three hours. Hearing thresholds were determined by recording auditory brainstem responses to clicks and noise bursts (1-32 kHz) and were assessed a week prior to and immediately after exposure, as well as on days 1, 3, 7, 14, 21, and 28. Cochleae were prepared as whole-mounts or embedded and sectioned for histological analysis. RESULTS: Relative to the control treatments, Compound A failed to preserve auditory thresholds post-noise exposure with statistical significance. Histological analyses confirm the physiological result. CONCLUSION: The present findings suggest that Compound A does not have substantial otoprotective capacities in a noise trauma model.

[Study on Hydrothermal Preparation and Luminescence Properties of Luminescent Material BaSrMg(PO4)2:Eu³âº].

Eu³âº doped BaSrMg (PO4)2 were prepared by a hydrothermal method. The crystal structure and morphology of BaSrMg(PO4)2:Eu³âº phosphor were characterized by X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FESEM). The effects of different pH values (5, 6, 7 and 8) and different reaction temperatures (120, 140, 160, 180 and 200 °C) on the crystal structure and morphology of BaSrMg(PO4)2:Eu³âº phosphor were studied in this paper. The results of XRD indicate that diffraction peaks are sharp and strong only when pH value is 6, meanwhile the FESEM shows the morphology is regular-shaped. The XRD patterns show amorphous halos superimposed with several weak sharp peaks for the samples preparing under the pH values of 5, 7 and 8. It indicates that these three samples are solid solution or mixed phases, which are in accord with the results of FESEM. From the fluorescence spectra, the peaks in the excitation spectra were assigned to the transition from 7F0 to 5D4, 5L8, 5L6 and 5D2, while the peaks of emission spectra corresponding to the transition of 5D1 --> 7F1 and 5D0-->7Fj (J = 0, 1, 2, 3 and 4). The strongest emission peak of the optimized phosphor located at 613 nm (5D0--> 7F2), excited by the main excitation peak with wavelength of 394 nm. The splitting of the emission peaks changes depends on pH values and temperatures, which indicating that luminescence properties is closely related to the crystal structure and morphology of particles.

Alkaloids from Piper longum Exhibit Anti-inflammatory Activity and Synergistic Effects with Chemotherapeutic Agents against Cervical Cancer Cells.

Piper longum L. is widely cultivated for food, medicine, and other purposes in tropical and subtropical regions. Sixteen compounds including nine new amide alkaloids were isolated from the roots of P. longum. The structures of these compounds were determined by spectroscopic data. All compounds showed better anti-inflammatory activities (IC50 = 1.90 ± 0.68-40.22 ± 0.45 µM) compared to indomethacin (IC50 = 52.88 ± 3.56 µM). Among the isolated compounds, five dimeric amide alkaloids exhibited synergistic effects with three chemotherapeutic drugs (paclitaxel, adriamycin, or vincristine) against cervical cancer cells. Moreover, these dimeric amide alkaloids also enhanced the efficacy of paclitaxel in paclitaxel-resistant cervical cancer cells. The combination treatment of one of these dimeric amide alkaloids and paclitaxel promoted cancer cell apoptosis, which is related to the Src/ERK/STAT3 signaling pathway.

The bioactive amide alkaloids from the stems of Piper nigrum.

Piper nigrum is an important aromatic plant, and its fruits (black and white pepper) are commonly used as food additives and spices. However, its stems were disposed as wastes. This research comprehensively investigated bioactive alkaloids of the stems, eight new dimeric amide alkaloids and eight known compounds were obtained. All obtained compounds showed excellent anti-inflammatory activity. Additionally, the dimeric amide alkaloids enhanced the anticancer effect of paclitaxel against cervical cancer cells. These results demonstrate that the stems of P. nigrum could be the sustainable source of bioactive alkaloids for development and utilization in the food and health fields.

Antibacterial and Anti-inflammatory Effects of Clarithromycin-Loaded Poly(l-Lactide) Membrane in Rabbit Postoperation Model of Chronic Rhinosinusitis.

OBJECTIVE: Macrolide antibiotics are often used to prevent infection and inflammation after functional endoscopic sinus surgery for the treatment of chronic rhinosinusitis (CRS). The purpose of this study was to investigate the anti-inflammatory and antibacterial effects of the clarithromycin-loaded poly(-lactide) (CLA-PLLA) membrane and its mechanism. STUDY DESIGN: Randomized controlled trial. SETTING: Animal Experiment Center. METHODS: We compared the difference between poly(l-lactide) (PLLA) and CLA-PLLA membranes by observing the morphology of fibrous scaffolds, measuring water contact angle, tensile strength, and drug release capacity, and evaluating the antimicrobial activity of CLA-PLLA. Twenty-four rabbits were divided into a PLLA group and a CLA-PLLA group after establishing CRS models. Another 5 normal rabbits comprised the control group. After 3 months, we placed the PLLA membrane in the nasal cavity of the PLLA group and the CLA-PLLA membrane in the CLA-PLLA group. Then, 14 days later, we evaluated the histological and ultrastructural changes in the sinus mucosa, protein, and messenger RNA (mRNA) levels of interleukin (IL)-4, IL-8, tumor necrosis factor-α, transforming growth factor-ß1, α-smooth muscle actin, and type I collagen. RESULTS: The CLA-PLLA membrane showed no significant difference in physical performance to the PLLA membrane, which continuously released 95% of the clarithromycin (CLA) for 2 months. The CLA-PLLA membrane had significant bacteriostatic properties that can improve the morphology of mucosal tissues, and inhibit protein and mRNA expression of inflammatory cytokines. In addition, CLA-PLLA also inhibited the expression of fibrosis-associated marker molecules. CONCLUSION: The CLA-PLLA membrane released CLA slowly and continuously, providing antibacterial, anti-inflammatory, and antifibrotic effects in a rabbit model of postoperative CRS.

[Preparation and luminescence of single-host white-light-emitting BaSrMg(PO4)2 : Eu2+ phosphor for ultraviolet LEDs].

A single-host white-light-emitting phosphor BaSrMg(PO4)2 : EU2+ was prepared by high temperature solid-state reaction method, and the luminescence characteristics and XRD pattern were investigated. The results showthat BaSrMg(PO4)2 phase was obtained by sintering at 1 200 degrees C for 3 hours. BaSrMg(PO4)2 = Eu2+ phosphor exhibits two main emission bands peaking at 424 and 585 nm, respectively. The emission band peaking at 424 nm is attributed to the 4f 6 5d1 --> 4f7 transition of Eu2+ substituting Sr2+, while the emission band peaking at 585 nm originates from the 4f 6 5d1 --> 4f7 transition of Eu2+ replacing Ba2+ in host lattice. The excitation spectra of the two emission peaks are range from 250 to 400 nm and both peaking at 360 nm. The effect of the proportion of Ba and Sr, and the Eu2+ doping concentration on the emission intensity were discussed in detail. Different chromaticity coordinates were obtained for each phosphor, that is, the chromaticity coordinates of the designed phosphor is tunable for the white-emitting LED or for special purpose. Quantum efficiency was also examined for the phosphors with different Eu2+ doping concentration, and concentration quenching took place obviously when Eu2+ doping concentration was lager than 6% in mole ratio. The obtained phosphor BaSrMg(PO4)2 : Eu2+ can be excited by near ultraviolet radiation effectively and emit full color lighting, which is a promising single-host white-light-emitting phosphor for white LED.

Injectable and Self-Healing Hydrogel with Anti-Bacterial and Anti-Inflammatory Properties for Acute Bacterial Rhinosinusitis with Micro Invasive Treatment.

Systemic antibiotic therapy is the main treatment for acute bacterial rhinosinusitis (ABRS). However, this treatment often causes side effects of dizziness, diarrhea, and drug resistance. In this study, a new polyethylene glycol hydrogel (PEG-H) treatment model is developed to achieve sustained release of drugs at the locality while avoiding those adverse effects. The PEG-H is composed of 4-arm-PEG-SH and silver ions through a high affinity and dynamic reversible coordination bond between the thiol and silver ion. In the initial test, PEG-H is loaded with Clarithromycin (CAM-Lips@Hydrogel) or Clarithromycin and Budesonide liposomes (CAM+BUD-Lips@Hydrogel). The results show that PEG-H maintains the characteristics of self-healing, biodegradability, moderate swelling rate, injectibility and sustained drug release. In in vivo studies, the hydrogel is injected into the maxillary sinus of ABRS rabbit models. In both a single or combined load, the hydrogel not only plays an effective role as an anti-bacterial, but also inhibits inflammatory response of local sinus mucosa. In addition, no other side effects are observed in the ABRS rabbit model through behavioral observation and drug sensitivity tests. Therefore, the injectable self-healing hydrogel with anti-bacterial and anti-inflammatory properties provides a new micro invasive therapeutic method for the clinical treatment of ABRS.

Intratympanic application of poloxamer 407 hydrogels results in sustained N-acetylcysteine delivery to the inner ear.

N-acetylcysteine is a thiol-containing antioxidant, which has shown otoprotective effects in in vitro as well as in vivo models of cisplatin-induced hearing loss. Systemic administration of antioxidants, however, is associated with the major potential drawback of interference with the tumoricidal effect of cisplatin. This therapeutic limitation can be overcome by local intratympanic injection of the antioxidant N-acetylcysteine, which results in very restricted systemic uptake of the drug, whilst intracochlear drug levels are substantially higher. Furthermore, osmolality and pH properties of formulations for intratympanic injection need to be controlled, as they impact the fraction of drug crossing the barriers of the inner ear and could potentially damage middle and inner ear structures. This study focused on (i) the evaluation of concentration-time profiles of N-acetylcysteine in perilymph, cerebrospinal fluid and plasma after intratympanic administration, (ii) the influence of the dosage form, i.e. a thermoreversible poloxamer 407 hydrogel versus a solution, on N-acetylcysteine pharmacokinetics, and (iii) the development of a pH- and osmolality-adjusted formulation for intratympanic N-acetylcysteine delivery. 49 female albino guinea pigs were randomized into two treatment groups, receiving either a single intratympanic injection of a 4% N-acetylcysteine poloxamer 407 hydrogel or a 4% N-acetylcysteine solution. 8 animals served as untreated controls. N-acetylcysteine levels in perilymph, cerebrospinal fluid and plasma were monitored over a period of 24 h. Samples were taken at 1, 3, 6, 12 and 24 h (poloxamer 407 hydrogel group) and 1, 6 and 24 h (solution group) post injection, and analysed by high performance liquid chromatography-tandem mass spectrometry. Intratympanic application of the 4% N-acetylcysteine poloxamer 407 hydrogel resulted in a 4-fold larger perilymph area under the concentration-time curve (0-24 h) than topical administration of the equally concentrated N-acetylcysteine solution but in similar plasma N-acetylcysteine levels. N-acetylcysteine concentrations in the cerebrospinal fluid were below the level of detection (5 ng/ml) in both treatment groups. N-acetylcysteine-containing formulations applied to the middle ear were isohydric and osmolality was reduced by up to 200 mosmol/kg compared to equally concentrated formulations used in previous studies. In summary, we were able to demonstrate that the intratympanic injection of thermoreversible poloxamer 407 hydrogels increases and sustains N-acetylcysteine delivery to the inner ear. Given the low plasma N-acetylcysteine levels after topical application and the physiological pH and osmolality of the hydrogel, the risk of compromising the antineoplastic effects of cisplatin therapy and of local side effects is minimal.

Long-term effects and potential limits of intratympanic dexamethasone-loaded hydrogels combined with dexamethasone-eluting cochlear electrodes in a low-insertion trauma Guinea pig model.

Cochlear implantation has become the most effective hearing restoration method and is one of the great advances in modern medicine. Early implants have been continuously developed into more efficient devices, and electro-acoustic stimulation is increasingly expanding the indication criteria for cochlear implants to patients with more residual hearing. Therefore, protecting the cochlear structures and maintaining its intrinsic capacities like residual hearing has become more important than ever before. In the present study, we aimed to assess the long-term protective effects of a dexamethasone-eluting electrode combined with the preoperative intratympanic application of a dexamethasone-loaded thermoreversible hydrogel in a cochlear implant guinea pig model. 40 normal-hearing animals were equally randomized into a control group receiving an unloaded hydrogel and a non-eluting electrode, a group receiving a dexamethasone-loaded hydrogel and a non-eluting electrode, a group receiving an unloaded hydrogel and a dexamethasone-eluting electrode and a group receiving both a dexamethasone-loaded hydrogel and a dexamethasone-eluting electrode. Residual hearing and impedances were investigated during a period of 120 days. Tissue response and histological changes of cochlear structures were analyzed at the end of the experiments. Treatment with dexamethasone did not show a significant protective effect on residual hearing independent of treatment group. Although the majority of the cochleae didn't exhibit any signs of electrode insertion trauma, a small degree of tissue response could be observed in all animals without a significant difference between the groups. Foreign body giant cells and osteogenesis were significantly associated with tissue response. Hair cells, synapsin-1-positive cells and spiral ganglion cells were preserved in all study groups. Cochlear implantation using a dexamethasone-eluting electrode alone and in combination with a dexamethasone-loaded hydrogel significantly protected auditory nerve fibers on day 120. Post-implantation impedances were equal across study groups and remained stable over the duration of the experiment. In this study we were able to show that use of a dexamethasone-eluting electrode alone and in combination with preoperative application of dexamethasone-loaded hydrogel significantly protects auditory nerve fibers. Furthermore, we have shown that a cochlear implantation-associated hearing threshold shift and tissue response may not be completely prevented by the sole application of dexamethasone.

Cochlear Implantation in the Guinea Pig.

Cochlear implants are highly efficient devices that can restore hearing in subjects with profound hearing loss. Due to improved speech perception outcomes, candidacy criteria have been expanded over the last few decades. This includes patients with substantial residual hearing that benefit from electrical and acoustical stimulation of the same ear, which makes hearing preservation during cochlear implantation an important issue. Electrode impedances and the related issue of energy consumption is another major research field, as progress in this area could pave the way for fully implantable auditory prostheses. To address these issues in a systematic way, adequate animal models are essential. Therefore, the goal of this protocol is to provide an animal model of cochlear implantation, which can be used to address various research questions. Due to its large tympanic bulla, which allows easy surgical access to the inner ear, as well as its hearing range which is relatively similar to the hearing range of humans, the guinea pig is a commonly used species in auditory research. Cochlear implantation in the guinea pig is performed via a retroauricular approach. Through the bullostomy a cochleostomy is drilled and the cochlear implant electrode is inserted into the scala tympani. This electrode can then be used for electrical stimulation, determination of electrode impedances and the measurement of compound action potentials of the auditory nerve. In addition to these applications, cochlear implant electrodes can also be used as drug delivery devices, if a topical delivery of pharmaceutical agents to the cells or fluids of the inner ear is intended.

Effects of sustained release dexamethasone hydrogels in hearing preservation cochlear implantation.

It has been shown that glucocorticoids reduce the hearing threshold shifts associated with cochlear implantation. Previous studies evaluated the administration of glucocorticoids immediately before surgery or the repeated pre- or perioperative systemic application of glucocorticoids. The aim of this study was to evaluate the effects of a sustained release dexamethasone hydrogel in hearing preservation cochlear implantation. To address this issue, a guinea pig model of cochlear implantation was used. 30 normal hearing pigmented guinea pigs were randomized into a group receiving a single dose of a dexamethasone/poloxamer407 hydrogel one day prior to surgery, a second group receiving the hydrogel seven days prior to surgery and a control group. A silicone cochlear implant electrode designed for the use in guinea pigs was inserted to a depth of 5 mm through a cochleostomy. Compound action potentials of the auditory nerve (frequency range 0.5-32 kHz) were measured preoperatively, directly postoperatively and on postoperative days 3, 7, 14, 21 and 28. Following the last audiometry, temporal bones were harvested and histologically evaluated. Dexamethasone hydrogel application one day prior to surgery resulted in significantly reduced hearing threshold shifts at low, middle and high frequencies measured at postoperative day 28 (p < 0.05). Application of the hydrogel seven days prior to surgery did not show such an effect. Dexamethasone application one day prior to surgery resulted in increased outer hair cell counts in the cochlear apex and in reduced spiral ganglion cell counts in the basal and middle turn of the cochlea, a finding that was associated with a higher rate of electrode translocation in this group. In this study, we were able to demonstrate functional benefits of a single preoperative intratympanic application of a sustained release dexamethasone hydrogel in a guinea pig model of cochlear implantation.

Determination of the glycosylation-pattern of the middle ear mucosa in guinea pigs.

In the present study the glycosylation pattern of the middle ear mucosa (MEM) of guinea pigs, an approved model for middle ear research, was characterized with the purpose to identify bioadhesive ligands which might prolong the contact time of drug delivery systems with the middle ear mucosa (MEM). To assess the utility of five fluorescein labeled plant lectins with different carbohydrate specificities as bioadhesive ligands, viable MEM specimens were incubated at 4°C and the lectin binding capacities were calculated from the MEM-associated relative fluorescence intensities. Among all lectins under investigation, fluorescein-labeled wheat germ agglutinin (F-WGA) emerged as the highest bioadhesive lectin. In general, the accessibility of carbohydrate moieties of the MEM followed the order: sialic acid and N-acetyl-d-glucosamine (WGA)>>mannose and galactosamine (Lensculinaris agglutinin)>N-acetyl-d-glucosamine (Solanumtuberosum agglutinin)>fucose (Ulexeuropaeus isoagglutinin I)>>terminal mannose α-(1,3)-mannose (Galanthusnivalis agglutinin). Competitive inhibition studies with the corresponding carbohydrate revealed that F-WGA-binding was inhibited up to 90% confirming specificity of the F-WGA-MEM interaction. The cilia of the MEM were identified as F-WGA binding sites by fluorescence imaging as well as a z-stack of overlays of transmission, F-WGA- and nuclei-stained images of the MEM. Additionally, co-localisation experiments revealed that F-WGA bound to acidic mucopolysaccharides of the MEM. All in all, lectin-mediated bioadhesion to the MEM is proposed as a new concept for drug delivery to prolong the residence time of the drug in the tympanic cavity especially for successful therapy for difficult-to-treat diseases such as otitis media.

Vascular endothelial growth factor expression in nasal polyps of aspirin-intolerant patients.

OBJECTIVE: To study differences between aspirin-tolerant patients and aspirin-intolerant patients concerning vascular endothelial growth factor (VEGF) expression. Recent publications strongly suggest the involvement of VEGF and its receptors in the pathophysiologic process of nasal polyps. DESIGN: We subjected 43 polyp specimens to semiquantitative immunohistochemical analysis. We quantified VEGF and its receptors (Flk, Flt, and neuropilin) in all samples. To gain insight into potential VEGF-mediated cellular responses, we determined proliferative (Ki67) and apoptotic (caspase 3) indices. PATIENTS: Polyp samples were obtained from 22 aspirin-intolerant patients and from 21 aspirin-tolerant patients, and control specimens were obtained from 24 subjects with healthy nasal respiratory mucosa. SETTING: Laboratory; Department of Otorhinolaryngology-Head and Neck Surgery, University Medical Center of the Johannes Gutenberg University Mainz, Mainz, Germany. MAIN OUTCOME MEASURES: Expression levels of VEGF, VEGF receptors. and proliferative and apoptotic indices. RESULTS: We found higher expressed levels of VEGF and neuropilin and stronger proliferation in nasal polyps from aspirin-tolerant and aspirin-intolerant patients compared with controls. In polyps from aspirin-intolerant patients, VEGF was expressed at considerably higher levels compared with those from aspirin-tolerant subjects. Apoptotic activity remained unchanged in all 3 groups. CONCLUSIONS: Nasal polyps from aspirin-tolerant and aspirin-intolerant patients are characterized by strong proliferation and high levels of VEGF and neuropilin expression. Nasal polyps from aspirin-intolerant patients show distinctly increased VEGF levels. The relevance of these findings for future therapeutic approaches is yet to be determined.