Injectable Poloxamer Hydrogel Formulations for Intratympanic Delivery of Dexamethasone.

BACKGROUND: In this study, we prepared and evaluated an injectable poloxamer (P407) hydrogel formulation for intratympanic (IT) delivery of dexamethasone (DEX). METHODS: DEX-loaded P407 hydrogels were characterized in terms of thermogelation, drug loading capacities, particle size, and drug release. The in vivo toxicity and drug absorption of the DEX-loaded P407 formulation after IT injection were evaluated using an animal model by performing histopathological analysis and drug concentration measurements. RESULTS: The P407 hydrogel effectively solubilized hydrophobic DEX and demonstrated a sustained release compared to the hydrophilic DEX formulation. The in vivo study showed that the hydrogel formulation delivered considerable drug concentrations to the inner ear and displayed a favorable safety profile without apparent cytotoxicity or inflammation. CONCLUSION: P407 hydrogel can be useful as an injectable inner ear delivery formulation for hydrophobic drugs due to their biocompatibility, drug-solubilizing capacity, thermogelation, and controlled release.

Injectable glycol chitosan thermogel formulation for efficient inner ear drug delivery.

We prepared a new injectable thermogel to enhance the efficiency of inner ear delivery of dexamethasone (DEX). Hexanoyl glycol chitosan (HGC) was synthesized and evaluated as an amphiphilic thermogel (Tgel ~ 32 °C) for use as a solubilizing agent as well as an injectable carrier for intratympanic delivery of the hydrophilic and hydrophobic forms of DEX. Various thermogel formulations with different drug types and concentrations were prepared, and their physicochemical and thermogelling properties were characterized by 1H NMR, ATR-FTIR, and rheometer. They exhibited versatile release kinetics from several hours to more than 2 weeks, depending on drug type and concentration. Our formulations further showed good residual stability for more than 21 days without any cytotoxicity or inflammation in the middle and inner ear and could deliver a considerably high drug concentration into the inner ear. Therefore, HGC thermogel has great potential as an effective and safe formulation for inner ear drug delivery.

Non-cell adhesive hexanoyl glycol chitosan hydrogels for stable and efficient formation of 3D cell spheroids with tunable size and density.

Three-dimensional (3D) culture systems that provide a more physiologically similar environment than conventional two-dimensional (2D) cultures have been extensively developed. Previously we have provided a facile method for the formation of 3D spheroids using non-adhesive N-hexanoyl glycol chitosan (HGC) hydrogel-coated dishes, but with limitations such as low gel stability and weak mechanical properties. In this study, chemically crosslinked hydrogels were prepared by photocrosslinking of methacrylated HGCs (M-HGCs), and their spheroid-forming abilities were evaluated for long-term 3D cell cultures. The M-HGC hydrogels demonstrated not only enhanced gel stability, but also good spheroid-forming abilities. Furthermore, the M-HGC-coated dishes were effective in generating spheroids of larger size and higher cell density depending on the crosslinking density of the M-HGCs. These results indicate that our hydrogel-coated dish system could be widely applied as an effective technique to produce cell spheroids with customized sizes and densities that are essential for tissue engineering and drug screening.

Endurance exercise training restores atrophy-induced decreases of myogenic response and ionic currents in rat skeletal muscle artery.

Atrophic limbs exhibit decreased blood flow and histological changes in the arteries perfusing muscles. However, the effect of atrophy on vascular smooth muscle function is poorly understood. Here, we investigated the effect of unilateral sciatic denervation on the myogenic response (MR) and the ionic currents in deep femoral artery (DFA) smooth muscles from Sprague-Dawley rats. Because denervated rats were capable of treadmill exercise (20 m/min, 30 min, 3 times/wk), the impact of exercise training on these effects was also assessed. Skeletal arteries were harvested 3 or 5 wk after surgery. Then skeletal arteries or myocytes were subjected to video analysis of pressurized artery, myography, whole-cell patch clamp, and real-time quantitative PCR to determine the effect of hindlimb paralysis in the presence/absence of exercise training on MR, contractility, ionic currents, and channel transcription, respectively. In sedentary rats, atrophy was associated with loss of MR in the DFA at 5 wk. The contralateral DFA had a normal MR. At 5 wk after surgery, DFA myocytes from the atrophic limbs exhibited depressed L-type Ca2+ currents, GTPγS-induced transient receptor potential cation channel (TRPC)-like currents, 80 mM KCl-induced vasoconstriction, TRPC6 mRNA, and voltage-gated K+ and inwardly rectifying K+ currents. Exercise training abrogated the differences in all of these functions between atrophic side and contralateral side DFA myocytes. These results suggest that a probable increase in hemodynamic stimuli in skeletal artery smooth muscle plays an important role in maintaining MR and ionic currents in skeletal artery smooth muscle. This may also explain the observed benefits of exercise in patients with limb paralysis. NEW & NOTEWORTHY Myogenic responses (MRs) in rat skeletal arteries feeding the unilateral atrophic hindlimb were impaired. In addition, the L-type Ca2+ channel current, the TRPC6-like current, and TRPC6 mRNA levels in the corresponding myocytes decreased. Voltage-gated K+ channel currents and inwardly rectifying K+ channel currents were also attenuated in atrophic side myocytes. Exercise training effectively abrogated electrophysiological dysfunction of atrophic side myocytes and prevented loss of the MR.

Maxi-K channel (BKCa) activity veils the myogenic tone of mesenteric artery in rats.

Arterioles and small arteries change their tone in response to transmural pressure changes, called myogenic tone (MT). In comparison to the branches of cerebral arteries (CA) showing prominent MT, the third branches of mesenteric arteries (MA) with similar diameters show weaker MT Here, we aimed to analyze the electrophysiological differences responsible for the weaker MT in MA (MTMA) than MT in CA (MTCA). We measured ionic current using patch clamp in isolated MA smooth muscle cells (MASMCs) and CA smooth muscle cells (CASMCs) of rats. MT was analyzed using video analysis of pressurized small arteries. Quantitative-PCR (q-PCR) and immunofluorescence confocal microscopy were used to compare the mRNA and protein expression level of big-conductance Ca2+-activated K+ channel (BKCa) subunits (Slo1α and Sloß1). Whole-cell patch clamp study revealed higher density of voltage-operated Ca2+ channel current (ICaV) in the MASMCs than in CASMCs. Although voltage-gated K+ channel current (IKv) was also higher in MASMCs, treatment with Kv inhibitor (4-aminopyridine) did not affect MTMA Interestingly, BKCa current density and the frequency of spontaneous transient outward currents (STOCs) were consistently higher in MASMCs than in CASMCs. Inside-out patch clamp showed that the Ca2+-sensitivity of BKCa is higher in MASMCs than in CASMCs. Iberiotoxin, a selective BKCa inhibitor, augmented MTMA by a larger extent than MTCA Although q-PCR analysis did not reveal a significant difference of mRNAs for Slo1α and Sloß1, immunofluorescence image suggested higher expression of Slo1α in MASMCs than in CASMCs. Despite the large ICaV density, the high activities of BKCa including the more frequent STOCs in MASMCs veils the potentially strong MTMA.