Shuai Shi

In situ covalently cross-linked PEG hydrogel for ocular drug delivery applications

Avastin(®) has been clinically proved to be effective in the treatment of intraocular neovascularization diseases. However, the short half-life of Avastin(®) need frequent administration to maintain its therapeutic efficiency. In this paper, we attempted to develop an in situ PEG hydrogels with great biocompatibility for sustained release of Avastin(®) to inhibit the corneal neovascularization. PEG hydrogels was formed via thiol-maleimide reaction using 4-arm PEG-Mal and 4-arm PEG-SH. The transparent hydrogel was rapidly formed under physiological conditions. By varying the concentration of 4-arm PEG-SH, PEG hydrogel with different gelling time, pore size, swelling ratio and mechanical property could be obtained. In vitro cytotoxicity indicated that the developed PEG hydrogel had no apparent cytotoxicity on L-929 cells after 7 days of incubation. In vitro release study showed the encapsulated Avastin(®) was sustained release from PEG hydrogels within a period of 14 days study. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis further confirmed that the released Avastin(®) did not undergo apparent hydrolysis within 14 days. As a conclusion, we could conclude that the developed PEG hydrogels as an injectable hydrogels might be suitable for extended Avastin(®) release to treat the corneal neovascularization.

Fabrication of a Micellar Supramolecular Hydrogel for Ocular Drug Delivery

In this paper, we describe a simple method for constructing a micellar supramolecular hydrogel, composed of a low-molecular-weight methoxy poly(ethylene glycol) (Mn = 2000 Da) block polymer and α-cyclodextrin (α-CD), for topical ocular drug delivery. Adding aqueous block polymer micelles into an α-CD aqueous solution resulted in the formation of a micellar supramolecular hydrogel through host-guest inclusion. The effects of the drug payload, block polymer, and α-CD concentrations as well as the block polymer structure on gelation time were investigated. The resultant micellar supramolecular hydrogels were thoroughly characterized by X-ray diffraction, rheological studies, and scanning electron microscopy. The hydrogels exhibited thixotropic properties, which are beneficial to ocular drug delivery. In vitro release studies indicated that the α-CD concentration strongly influenced the release rate of diclofenac (DIC) from supramolecular hydrogel. The hydrogels showed relatively low cytotoxicity toward L-929 and HCEC cells and did not significantly affect the migration of the latter after 24 h incubation. The hydrogel was nonirritant toward the rabbit eye, as indicated by the Draize test, fluorescein staining, and histological observation. Nile Red-labeled micellar supramolecular hydrogel showed that it could significantly extend the retention time on the corneal surface in rabbits, compared with a plain micellar formulation. In vivo pharmacokinetics indicated that the hydrogel could greatly improve ocular drug bioavailability, compared with that of micellar formulation. Our results suggest that the micellar supramolecular hydrogel is a promising system for ocular drug delivery.

Chitosan grafted methoxy poly(ethylene glycol)-poly(ε-caprolactone) nanosuspension for ocular delivery of hydrophobic diclofenac

This study aimed to develop a cationic nanosuspension of chitosan (CS) and methoxy poly(ethylene glycol)-poly(ε-caprolactone) (MPEG-PCL) for ocular delivery of diclofenac (DIC). MPEG-PCL-CS block polymer was synthesized by covalent coupling of MPEG-PCL with CS. The critical micelle concentration of the MPEG-PCL-CS block polymer was 0.000692 g/L. DIC/MPEG-PCL-CS nanosuspension (mean particle size = 105 nm, zeta potential = 8 mV) was prepared and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and differential scanning calorimetry. The nanosuspension was very stable without apparent physical property changes after storage at 4 °C or 25 °C for 20 days, but it was unstable in the aqueous humor solution after 24 h incubation. Sustained release of the encapsulated DIC from the nanosuspension occurred over 8 h. Neither a blank MPEG-PCL-CS nanosuspension nor a 0.1% (mass fraction) DIC/MPEG-PCL-CS nanosuspension caused ocular irritation after 24 h of instillation. Enhanced penetration and retention in corneal tissue was achieved with a Nile red/MPEG-PCL-CS nanosuspension compared with a Nile red aqueous solution. In vivo pharmacokinetics studies showed enhanced pre-corneal retention and penetration of the DIC/MPEG-PCL-CS nanosuspension, which resulted in a higher concentration of DIC (Cmax) in the aqueous humor and better bioavailability compared with commercial DIC eye drops (P < 0.01).

An injectable thermosensitive polymeric hydrogel for sustained release of Avastin® to treat posterior segment disease.

Delivery of drugs, especially bioactive macromolecules such as proteins and nucleic acids, to the posterior segment is still a significant challenge for pharmaceutical scientists. In the present study, we developed an injectable thermosensitive polymeric hydrogel for sustained release of Avastin(®) to treat posterior segment disorders. The payload of Avastin(®) to poly(lactic acid-co-glycolic acid)-poly(ethylene glycol)-poly(lactic acid-co-glycolic acid) (PLGA-PEG-PLGA) hydrogel did not influence its inherent sol-gel transition behavior, but shifted the sol-gel transition to a lower temperature. The resulting Avastin(®)/PLGA-PEG-PLGA hydrogels had a porous structure (pore size, 100 ∼ 150 μm) as determined by scanning electron microcopy (SEM), facilitating sustained Avastin(®) release over a period of up to 14 days in vitro. The PLGA-PEG-PLGA hydrogel was immediately formed in the vitreous humor after intravitreal injection, followed by slow clearance over an 8 week study period. The PLGA-PEG-PLGA hydrogel exhibited no apparent toxicity against retinal tissue, as indicated by the absence of inflammation, retinal necrosis, and stress responses, using optical coherence tomography (OCT) and histological/immunochemical analyses. Electrophysiology (ERG) examination also showed that the PLGA-PEG-PLGA hydrogel did not affect retinal function. In vivo pharmacokinetic studies indicated that the use of the PLGA-PEG-PLGA hydrogel greatly extended the release of Avastin(®) over time in the vitreous humor and retina after intravitreal injection. Together, these results demonstrated that the PLGA-PEG-PLGA hydrogel was a promising candidate for ocular drug delivery of Avastin(®)via intravitreal injection.

Thermosensitive PEG–PCL–PEG (PECE) hydrogel as an in situ gelling system for ocular drug delivery of diclofenac sodium

Abstract Development of efficient ocular drug delivery systems was still a challenging task. The objective of this article was to develop a thermosensitive PEG–PCL–PEG (PECE) hydrogel and investigate its potential application for ocular drug delivery of diclofenac sodium (DIC). PECE block polymers were synthesized by coupling MPEG-PCL co-polymer using IPDI reagent, and then its sol–gel transition as a function with temperature was investigated by a rheometer. The results showed that 30% (w/v) PECE aqueous solution exhibited sol–gel transition at approximately 35 °C. In vitro release profiles showed the entrapped DIC was sustained release from PECE hydrogels up to 7 days and the initial drug loading greatly effect on release behavior of DIC from PECE hydrogels. MTT assay results indicated that no matter PECE or 0.1% (w/v) DIC-loaded PECE hydrogels were nontoxic to HCEC and L929 cells after 24 h culturing. In vivo eye irritation test showed that the instillation of either 30% (w/v) PECE hydrogels or 0.1% (w/v) DIC-loaded PECE hydrogels to rabbit eye did not result in eye irritation within 72 h. In vivo results showed that the AUC0–48 h of 0.1% (w/v) DIC-loaded PECE hydrogels exhibited 1.6-fold increment as compared with that of commercial 0.1% (w/v) DIC eye drops, suggesting the better ophthalmic bioavailability could be obtained by the instillation of 0.1% (w/v) DIC-loaded PECE hydrogels.

Self-assembled peptide-based supramolecular hydrogel for ophthalmic drug delivery

Conventional ophthalmic formulations such as eye drops normally suffer from limited therapeutic efficacy with a requirement for frequent instillation. To improve convenience and efficacy, a peptide-based supramolecular hydrogel (Nap-GFFY) was fabricated and tested for ophthalmic drug delivery. Diclofenac sodium (DIC), as a model drug, was encapsulated into the supramolecular hydrogel by simple physical mixing and then thoroughly characterized by transmission electron microscopy (TEM) and rheology. The encapsulated DIC was rapidly released from the supramolecular hydrogel over a period of 24 h study. In vitro cytotoxicity indicated that the developed Nap-GFFY hydrogel was nontoxic against different cell lines (HCEC, HLEC and L929 cells) after incubation for 24 h. Furthermore, an ocular tolerance test suggested that the developed DIC-loaded Nap-GFFY hydrogel gave rise to no eye irritation after a single instillation. More importantly, the drug concentration in the aqueous humor at 1 h after instillation of the DIC/Nap-GFFY hydrogel was significantly higher than that of commercial DIC eye drops (0.1% DIC; w/v), which indicated better corneal penetration and ophthalmic bioavailability. Overall, the developed DIC/Nap-GFFY hydrogel, as a promising ocular formulation, might have potential applications in the treatment of anterior segment disorders.

Supramolecular hydrogel of non-steroidal anti-inflammatory drugs: preparation, characterization and ocular biocompatibility

A supramolecular hydrogel based on a peptide (GFFY) and non-steroidal anti-inflammatory drugs (naproxen and ibuprofen) was synthesized for use as a topical gel. Using a heating–cooling strategy, the drug–peptide derivatives could self-assemble into nanofibers in aqueous solution to produce a supramolecular hydrogel. The different drug molecules used as the capping group had a profound effect on the self-assembly behaviour measured by circular dichroism. The supramolecular hydrogels were confirmed by rheological measurements to be thixotropic and had no apparent toxicity in vitro against HCEC and L-929 cells after 24 h incubation. More importantly, an in vivo ocular biocompatibility test indicated that the supramolecular hydrogels were well tolerated in rabbits and had satisfactory ocular biocompatibility, suggesting that they are promising candidates for the delivery of ocular drugs.

Cationic micelle based vaccine induced potent humoral immune response through enhancing antigen uptake and formation of germinal center

Nanoparticles have been proven to be an effective vaccine delivery system that can boost immune responses to subunit vaccines. Herein, we developed and characterized a cationic polymeric polyethylene glycol2000-poly ϵ-caprolactone2000-polyethylenimine2000 (mPEG2000-PCL2000-g-PEI2000) micelle as a potent vaccine delivery system to boost the immune response in vivo. The micelles that we developed exhibited great antigen-loading capability and minimal cytotoxicity in vitro. Meanwhile, micelles facilitated OVA antigen uptake by dendritic cells both in vitro and in vivo. More importantly, a micelle-formulated OVA vaccine could significantly promote anti-OVA antibody production by 190-fold and potently enhance T cell proliferation and the secretion of IL-5 and IFN-γ. We attributed these effects to its ability to promote antigen uptake, antigen deposition, and germinal center formation. In conclusion, the mPEG2000-PCL2000-PEI2000 micelle that we developed has potential as potent vaccine delivery system to induce Th2 immune response.

Visual tracing of diffusion and biodistribution for amphiphilic cationic nanoparticles using photoacoustic imaging after ex vivo intravitreal injections

To visually trace the diffusion and biodistribution of amphiphilic cation micelles after vitreous injection, various triblock copolymers of monomethoxy poly(ethylene glycol)–poly(ε-caprolactone)–polyethylenimine were synthesized with different structures of hydrophilic and hydrophobic segments, followed by labeling with near-infrared fluorescent dye Cyanine5 or Cyanine7. The micellar size, polydispersity index, and surface charge were measured by dynamic light scattering. The diffusion was monitored using photoacoustic imaging in real time after intravitreal injections. Moreover, the labeled nanoparticle distribution in the posterior segment of the eye was imaged histologically by confocal microscopy. The results showed that the hydrophilic segment increased vitreous diffusion, while a positive charge on the particle surface hindered diffusion. In addition, the particles diffused through the retinal layers and were enriched in the retinal pigment epithelial layer. This work tried to study the diffusion rate via a simple method by using visible images, and then provided basic data for the development of intraocular drug carriers.

Preparation and evaluation of teniposide-loaded polymeric micelles for breast cancer therapy.

Self-assembled polymeric micelles have been widely applied in anticancer drug delivery systems. Teniposide is a broad spectrum and effective anticancer drug, but its poor water-solubility and adverse effects of commercial formulation (VM-26) restrict its clinical application. In this work, teniposide-loaded polymeric micelles were prepared based on monomethoxy-poly(ethylene glycol)-poly(ε-caprolactone-co-d,l- lactide) (MPEG-PCLA) copolymers through a thin-film hydration method to improve the hydrophilic and reduce the systemic toxicity. The prepared teniposide micelles were without any surfactants or additives and monodisperse with a mean particle size of 29.6±0.3nm. The drug loading and encapsulation efficiency were 18.53±0.41% and 92.63±2.05%, respectively. The encapsulation of teniposide in MPEG-PCLA micelles showed a slow and sustained release behavior of teniposide in vitro and improved the terminal half-life (t1/2), the area under the plasma concentration-time curve (AUC) and retention time of teniposide in vivo compared with VM-26. In addition, teniposide micelles also enhanced the cellular uptake by MCF-7 breast cancer cells in vitro and increased the distribution in tumors in vivo. Teniposide micelles showed an excellent safety with a maximum tolerated dose (MTD) of approximately 50mg teniposide/kg body weight, which was 2.5-fold higher than that of VM-26 (about 20mg teniposide/kg body weight). Furthermore, the intravenous application of teniposide micelles effectively suppressed the growth of subcutaneous MCF-7 tumor in vivo and exhibited a stronger anticancer effect than that of VM-26. These results suggested that we have successfully prepared teniposide-loaded MPEG-PCLA micelles with improved safety, hydrophilic and therapeutic efficiency, which are efficient for teniposide delivery. The prepared teniposide micelles may be promising in breast cancer therapy.