Jiaxin Pi

Comparison of systemic absorption between ofloxacin ophthalmic in situ gels and ofloxacin conventional ophthalmic solutions administration to rabbit eyes by HPLC–MS/MS

In recent years, many pharmaceutical scientists have focused on developing the in situ gel-forming systems to overcome the poor bioavailability and therapeutic response exhibited by conventional ophthalmic solutions due to rapid pre-corneal elimination of the drug. The present work was to compare the systemic absorptions of ophthalmic ofloxacin in situ gel with the conventional ofloxacin eye drop after topical instillation to rabbit eyes by HPLC-MS/MS method and also determine the relative contribution of the nasal and the conjunctival mucosae to systemic ofloxacin absorption following topical instillation. The systemic AUC, Cmax, Tmax and Ke for ophthalmic in situ gel and ophthalmic solution after ocular instillation were 202.63±118.85 and 202.25±57.74 ng mL(-1) h, 54.22±28.31 and 48.4±25.97 ng mL(-1), 1.08±0.20 and 1.25±0.88 h, 0.0576±0.0207 and 0.0388±0.0248, respectively. And the values for the ratios of the AUC of anterior chamber of rabbit eye to blood plasma, AUCac/AUCpl, for ofloxacin conventional eye drop and in situ gel were 0.25 and 0.52, respectively. Statistic results showed that there was no significant difference in systemic absorption between the test groups and the reference groups (P>0.05) as both formulations have an AUCsa/AUCpl of 0.35. Therefore, the ophthalmic in situ gel may not decrease the drugs systemic absorption when administered in an equivalent dose as ophthalmic solutions into the rabbit eyes.

Salvianolic acid B protects against myocardial damage caused by nanocarrier TiO 2 ; and synergistic anti-breast carcinoma effect with curcumin via codelivery system of folic acid-targeted and polyethylene glycol-modified TiO 2 nanoparticles

Targeted delivery by the folate ligand is an effective way to enhance an anti-breast carcinoma effect, due to its high affinity for the folate receptor, which is overexpressed in many tumor cells. In this study, we firstly synthesized a folic acid (FA)-targeted and polyethylene glycol (PEG)-modified TiO2 nanocarrier. Then, an FA-PEG-TiO2 nanoparticle (NP) codelivery system loaded with curcumin and salvianolic acid B were prepared by emulsion evaporation–solidification at low temperature. The obtained folate-targeted NPs (FA-NPs) showed more cytotoxicity on MCF7 cells and MDA-MB-231 cells than a nontargeted NP group. Apart from a synergistic anti-breast cancer effect with curcumin, salvianolic acid B protects the cardiovascular system from oxidative injury by the TiO2 nanocarrier. With coumarin 6 as a fluorescent probe to observe cellular uptake of NPs, the results of in vitro cellular uptake demonstrated FA-NPs exhibited higher cellular uptake and accumulation in MCF7 cells and MDA-MB-231 cells than nontargeted NPs. Then, in vivo biodistribution of NPs was further qualitatively and quantitatively confirmed by in vivo imaging. More importantly, the animal study further suggested that FA-NPs had significantly stronger antitumor effects via receptor-mediated targeted delivery. Consequently, FA-PEG-TiO2 NPs loaded with curcumin and salvianolic acid B could be a promising drug-delivery system to treat breast cancer.

Ursolic Acid Nanocrystals for Dissolution Rate and Bioavailability Enhancement: Influence of Different Particle Size

BACKGROUND Ursolic acid (UA), a natural pentacyclic triterpenoid, has been reported to possess a variety of pharmacological activities, but the poor oral bioavailability of UA owing to the poor aqueous solubility and membrane permeability limits the further clinical application. OBJECTIVE The purpose of the present study was to develop UA nanocrystals and microcrystals employing high pressure homogenization (HPH) and to evaluate their effects on UA oral bioavailability. METHOD The crystalline morphology of UA nanocrystals and microcrystals prepared by HPH was observed by scanning electron microscopy and the crystalline state was characterized by differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). The dissolution rate of UA nanocrystals in different pH conditions was tested. Oral bioavailability of UA nanocrystals and microcrystals comparing with UA coarse suspension was evaluated in SD rats after 50 mg·kg-1 administration. RESULTS UA nanocrystals and microcrystals, the size of which ranged between 291.7 nm and 1299.3 nm were obtained. The results of DSC and PXRD revealed a degree of crystalline-amorphous transformation during HPH preparation. A significant increase was observed in the dissolution rate of UA nanocrystals. The relative bioavailability of UA nanocrystals and microcrystals exhibited 2.56 and 1.40-fold enhancement than that of UA coarse suspension, respectively, along with an increased peak concentration and a prolonged retention. CONCLUSION The nanosized UA crystal is a viable and efficient approach to improve the oral bioavailability of UA.

Increasing Efficacy and Reducing Systemic Absorption of Brimonidine Tartrate Ophthalmic Gels in Rabbits

Abstract Systemic absorption of ocularly administered Brimonidine Tartrate has been reported to give rise to several side-effects. Hence, it has become crucial to develop a delivery system that could increase efficacy and reduce systemic absorption. Therefore, the present work aims to develop Brimonidine Tartrate gels with different concentrations (0.05%, 0.1%, and 0.2% w/v, respectively) using Carbopol 974 P and HPMC E4M, and compare the therapeutic efficacy and systemic absorption with that of eye drop (0.2%, w/v) by UPLC-MS/MS. The result of histological analysis did not show any morphological or structural changes after the administration of formulations. In vitro residence time studies demonstrated that the gels exhibited a better precorneal residence time as compared with the eye drop. The gels with lower concentrations of the drug (0.05% and 0.1%, w/v) could significantly decrease intraocular pressure (IOP) in both normal and water-loaded rabbits as compared to the eye drop. Finally, the values of the ratio of AUC(0→∞) in comparison to eye drop showed the gels with lower concentrations of Brimonidine Tartrate could decrease the systemic absorption. From the result, it can be concluded the 0.1% ophthalmic gel has a potential to improve therapeutic efficacy and reduce the potential toxicity caused by systemic absorption.

A strategy to improve the oral availability of baicalein: The baicalein-theophylline cocrystal

Baicalein (BE) is a flavonoid compound derived from the roots of Scutellaria baicalensis. It has widely been used as anti-oxidant, anti-virus, anti-bacteria, anti-inflammatory and anti-allergic therapies. Due to its poor water solubility (16.82 μg/ml), the therapeutic effectiveness and oral bioavailability of Baicalein are highly limited. The purpose of this study was to investigate the possibility of baicalein-theophylline (BE-TH) cocrystals to achieve the simultaneous enhancement in dissolution and oral bioavailability of BE. The cocrystal had the new characteristic of scanning electron microscopy, differential scanning calorimetry thermograms and X-ray powder diffraction. Compared with coarse powder of BE, BE-TH cocrystals had significantly improved the solubility of BE. The dissolution test showed that the BE-TH cocrystals demonstrated 2.2-fold and 7.1-fold higher rate of dissolution than that of BE coarse powder in HCl (pH = 1.2) and phosphate buffer (PBS, pH = 6.8), respectively. Moreover, the cocrystals exhibited a 5.86-fold higher area under the curve in rats after the oral administration. This investigation enriched the present understanding of cocrystals on their behavior in vitro and in vivo, and built the groundwork for future development of BE as a promising compound into efficacious drug products.

Study of penetration mechanism of labrasol on rabbit cornea by Ussing chamber, RT-PCR assay, Western blot and immunohistochemistry

Labrasol, as a non-ionic surfactant, can enhance the permeation and absorption of drugs, and is extensively used in topical, transdermal, and oral pharmaceutical preparations as an emulsifier and absorption enhancer. Recent studies in our laboratory have indicated that labrasol has a strong absorption enhancing effect on different types of drugs in vitro and in vivo. This study was performed to further elucidate the action mechanism of labrasol on the corneal penetration. In this research, the fluorescein sodium, a marker of passive paracellular transport of tight junction, was selected as the model drug to assess the effect of labrasol on in vitro corneal permeability. To investigate the continuous and real-time influence of labrasol on the membrane permeability and integrity, the Ussing chamber system was applied to monitor the electrophysiological parameters. And, furthermore, we elucidated the effect of labrasol on excised cornea at the molecular level by application of RT-PCR, Western blot, and immunohistochemical staining. The results indicated that labrasol obviously enhance the transcorneal permeability of fluorescein sodium, and the enhancement was realized by interacting with and down-regulating the associated proteins, such as F-actin, claudin-1 and β-catenin, which were contributed to cell-cell connections, respectively.

A nano-cocrystal strategy to improve the dissolution rate and oral bioavailability of baicalein

Baicalein (BE) is one of the main active flavonoids representing the variety of pharmacological effects including anticancer, anti-inflammatory and cardiovascular protective activities, but its very low solubility, dissolution rate and poor oral absorption limit the therapeutic applications. In this work, a nano-cocrystal strategy was successfully applied to improve the dissolution rate and bioavailability of BE. Baicalein-nicotinamide (BE-NCT) nano-cocrystals were prepared by high pressure homogenization and evaluated both in vitro and in vivo. Physical characterization results including scanning electron microscopy, dynamic light scattering, powder X-ray diffraction and differential scanning calorimetry demonstrated that BE-NCT nano-cocrystals were changed into amorphous state with mean particle size of 251.53 nm. In the dissolution test, the BE-NCT nano-cocrystals performed 2.17-fold and 2.54-fold enhancement than BE coarse powder in FaSSIF-V2 and FaSSGF. Upon oral administration, the integrated AUC0 − t of BE-NCT nano-cocrystals (6.02-fold) was significantly higher than BE coarse powder (1-fold), BE-NCT cocrystals (2.87-fold) and BE nanocrystals (3.32-fold). Compared with BE coarse powder, BE-NCT cocrystals and BE nanocrystals, BE-NCT nano-cocrystals possessed excellent performance both in vitro and in vivo evaluations. Thus, it can be seen that nano-cocrystal is an appropriate novel strategy for improving dissolution rate and bioavailability of poor soluble natural products such as BE.

Pharmacokinetic and ocular microdialysis study of oral ginkgo biloba extract in rabbits by UPLC‐MS/MS determination

The purpose of this work was to determine and investigate the absorption of ginkgo terpenoids (GT) in plasma and aqueous humour after oral administration of ginkgo biloba extract (GBE) by UPLC‐MS/MS method.