Soliton and dispersive wave generation with third-order dispersion and temporal boundary.

We investigate the pulse evolution and energy conservation condition at the temporal boundary under third-order dispersion. When the fundamental soliton crosses the temporal boundary and forms two reflected pulses and one transmitted pulse, the power of the transmitted pulse first increases and then decreases as the incident spectrum shifts toward the blue side. If the transmitted spectrum lies in the anomalous group-velocity dispersion region, second-order soliton is formed and dispersive wave is radiated. We present a modified phase-matching condition to predict the resonance frequencies. The predicted results are in good agreement with the results obtained by numerically solving the nonlinear Schrödinger equation.

Effect of chirp on pulse reflection and refraction at a moving temporal boundary.

The reflection and refraction of chirped Gaussian pulse at a moving step refractive-index boundary are investigated. When a chirped Gaussian pulse crosses a temporal boundary, the shape of the reflected spectra is distorted by adjusting chirp parameters. However, the transmitted spectra retain the Gaussian shape. The shape of the final output spectra is the same if the absolute values of the chirp are the same. By changing the chirp values, we can control the energy of the reflected and transmitted pulses, and the splitting distance of the pulse at the temporal boundary. By adjusting the time-dependent refractive index, chirped Gaussian pulses can experience total internal reflection at the temporal boundary. When pulse splitting occurs in an anomalous dispersion region, the velocity of the transmitted pulse decreases.

Design and evaluation of baicalin-containing in situ pH-triggered gelling system for sustained ophthalmic drug delivery.

Baicalin has been reported to have anti-inflammatory and anti-cataract effects on eye tissues, but it has a low bioavailability partly due to its poor stability of baicalin, the special anatomic structure and efficient protective mechanism of eyes. The aim of this study was to investigate the correlation between the stability of baicalin and in situ pH-triggered gelling system. Carbopol(®) 974P (0.3%, w/v) was used as the gelling agent combined with hydroxypropylmethylcellulose E4M (0.6%, w/v) which acted as a viscosity enhancing agent. In vitro and in vivo evaluations were performed using several techniques, namely confocal scanning light microscopy analysis, rheometry, Gamma scintigraphic technique and microdialysis method. The rheological behavior showed a significant enhancement in gel strength under physiological conditions, and the formulation provided sustained release of the drug over an 8-h period. In elimination studies, the radioactivity of formulation was always higher than that of the control solution. Additionally, the AUC and C(max) values were 6.1-fold and 3.6-fold higher than those of the control solution, respectively. The results demonstrated that an in situ pH-triggered gelling system have better ability to keep baicalin stable and retain drug release than marketed baicalin eye drops to enhance the ocular bioavailability.

Preparation and evaluation of solid lipid nanoparticles of baicalin for ocular drug delivery system in vitro and in vivo.

PURPOSE: To prepare and evaluate the solid lipid nanoparticles of baicalin (BA-SLN) for ocular drug delivery system. METHODS: The BA-SLN was prepared by emulsification/ultrasonication method. The appearance of BA-SLN was examined by the negative stain method. The mean diameter and zeta potential of BA-SLN were determined using a Zetasizer. The entrapment efficiency of BA-SLN was determined by Sephadex-G50 column. And the solid-state characterization of BA-SLN was analyzed by DSC and X-ray. The release of drug from BA-SLN was evaluated using dialysis bag diffusion technique. The effects of SLN on corneal permeability of baicalin were investigated in vitro, using isolated rabbit corneas. The in vivo ocular irritation of BA-SLN was tested by pathological section observation using rabbits. The pharmacokinetics was evaluated by microdialysis in the rabbit aqueous humors. RESULTS: The results showed that the BA-SLN had an average diameter of 91.42 ± 1.02 nm with a zeta potential of -33.5 ± -1.28 mV and the entrapment efficiency of 62.45 ± 1.67%. In vitro release studies indicated that the BA-SLN retained the drug entity better than the baicalin ophthalmic solutions (BA-SOL). In the pharmacokinetics studies, the AUC value of BA-SLN was 4.0-fold versus the BA-SOL (P < 0.01), and the Cmax value of BA-SLN versus the BA-SOL was 5.3-fold (P < 0.01). CONCLUSION: SLN can be used as a carrier to enhance ocular bioavailability of baicalin.