Liposomal hypocrellin B as a potential photosensitizer for age-related macular degeneration: pharmacokinetics, photodynamic efficacy, and skin phototoxicity in vivo.

Photodynamic therapy (PDT) has been successfully implemented as a treatment for wet age-related macular degeneration (AMD), but very few photosensitizers have been developed for clinical use. Herein, we describe a novel formulation of liposomal hypocrellin B (LHB) that was prepared by high-pressure homogenization. The encapsulation efficiency and PDT efficacy in vitro of this new preparation were found to remain nearly constant over 1 year. Moreover, LHB is rapidly cleared from the blood, with a half-life of 2.319 ± 0.462 h and a very low serum concentration at 24 h after injection. Testing in a rat model of choroidal neovascularization (CNV) showed that leakage of blood vessels in CNV lesions was significantly reduced when LHB PDT was given at a dose of 1 mg kg(-1) along with yellow laser irradiation; the damage to the collateral retina and the retinal pigment epithelium was minimal. Skin phototoxicity assays showed that only two of the 200 mice given a 4 mg per kg dose of LHB experienced an inflammatory reaction in the auricle irradiated at 24 h after dosing. These data collectively indicate that LHB may be a safe and effective photosensitizer for vascular-targeted PDT of AMD.

A novel hypocrellin-based assembly for sonodynamic therapy against glioblastoma.

The non-invasive treatment of glioblastoma (GBM) is of great significance and can greatly reduce the complications of craniotomy. Sonodynamic therapy (SDT) is an emerging tumor therapeutic strategy that overcomes some fatal flaws of photodynamic therapy (PDT). Different from PDT, SDT has deep tissue penetration and can be applied in the non-invasive treatment of deep-seated tumors. However, effective sonosensitizers that can be used for SDT of GBM are still very rare. Herein, we have prepared a suitable assembly based on a hypocrellin derivative (CTHB) with good biocompatibility. Excitedly, the hypocrellin-based assembly (CTHB NPs) can effectively produce reactive oxygen species under ultrasound stimulation. The inherent fluorescence and photoacoustic imaging characteristics of the CTHB NPs are conducive to the precise positioning of the tumors. It has been proved both in subcutaneous and in intracranial tumor models that CTHB NPs can be used as an effective sonosensitizer to inhibit tumor growth under ultrasound irradiation. This hypocrellin-based assembly has a good clinical prospect in the non-invasive treatment of GBM.

Phenol biosensor based on hydrogel microarrays entrapping tyrosinase and quantum dots.

This paper describes the use of microarray-based biosensor system for the determination of phenol. Microarrays based on poly(ethylene glycol)(PEG) hydrogel were prepared by photopatterning of a solution containing PEG diacrylate (PEG-DA), photoinitiator, tyrosinase, and CdSe/ZnS quantum dots (QDs). During photo-induced crosslinking, tyrosinase and QDs were entrapped within the hydrogel microarrays, making the hydrogel microarray fluorescent and responsive to phenol. The entrapped tyrosinase could carry out enzyme-catalyzed oxidation of phenol to produce quinones, which subsequently quenched the fluorescence of QDs within hydrogel microarray. The fluorescence intensity of the hydrogel microarrays decreased linearly according to phenol concentration and the detection limit of this system was found to be 1.0 µM. The microarray system presented in this study could be combined with a microfluidic device as an initial step to create a phenol-detecting "micro-total-analysis-system (µ-TAS)".

Immobilization of tyrosinase on poly(indole-5-carboxylic acid) evidenced by electrochemical and spectroscopic methods.

A conducting, polymeric film of poly(indole-5 carboxylic acid) has been prepared by electrochemical polymerization for covalent immobilization of an enzyme belonging to the family of phenoloxidases-tyrosinase. The polymer was characterized by cyclic voltammetry, UV-VIS and Raman spectroscopy in a buffer solution. As the polymer contains pendant carboxylic groups one-step carbodiimide method was used to immobilize tyrosinase on the polymer matrix. Immobilization of tyrosinase was confirmed by surface enhanced resonance Raman scattering spectra (SERRS) and by cyclic voltammetry as well. Tyrosinase was shown to retain its biological activity when being immobilized on the polymer surface. As proved by the electrochemical and spectroelectrochemical (UV-VIS) experiments, tyrosinase covalently bonded to the polymer matrix effectively catalyzes oxidation of catechol. The reduction current of o-quinones was measured as a function of catechol concentration. The linear dependence was found to be 15 microM of catechol with sensitivity of 250 mA/M cm2.

Synthesis and EPR investigations of new aminated hypocrellin derivatives.

Hypocrellins are novel photodynamic agents. A recent advance in the synthesis of hypocrellin congeners results in the production of two amino-substituted hypocrellin B derivatives in high yield via photochemical reaction. Both compounds exhibit similar photodynamic activity as hypocrellin B in terms of type I and type II mechanisms. In anaerobic media, semiquinone anion radicals can be detected by electron paramagnetic resonance (EPR) under irradiation; while superoxide anion radical, hydroxyl radical and singlet oxygen are photoproduced when oxygen was present. The quantum yields of singlet oxygen by these two new compounds are determined to be 0.72 and 0.64, respectively, similar to that of hypocrellin B. The comparison of the photosensitization chemistry of compounds 1 and 2 in liposomes with that in homogeneous solution has also been made. In liposomes, the type II photoprocess was favored and predominant over the type I photoprocess due to the decreased interactions between dye molecules. Both compounds exhibit much stronger red light absorption than the parent hypocrellin and therefore, merit investigation as photosensitizers.

Quantitative and site-directed chemical modification of hypocrellins toward direct drug delivery and effective photodynamic activity.

For photodynamic therapy (PDT) treatment of microvascular diseases, drugs are delivered via blood circulation and the targets are vasculature endothelial cells, for which the contradictory requirements of hydrophilicity and lipophilicity of the drugs have been achieved by liposome preparations. Herein, it is demonstrated that the drug delivery and target affinity are achieved by a single chemical compound, hypocrellin B (HB) derivative 6 selected from three novel aminoalkanesulfonic acid HB derivatives, 5-7. 6 exhibits a much higher PDT activity (IC(50) = 22 nM) on human gastric carcinoma BGC823 cells than HB, while it has no cellular toxicity in the dark. On the basis of estimation of the clinically required concentration according to relative PDT activity and clinical criteria, it can be predicted that 6 is directly deliverable to and PDT effective on target cells. The enhanced red absorption and superhigh photoactivity suggest that 6 is more powerful for PDT of tumors than HB.

Electroactive self-assembled monolayers that permit orthogonal control over the adhesion of cells to patterned substrates.

This article describes an electroactive substrate that displays two independent dynamic functions for controlling the adhesion of cells. The approach is based on self-assembled monolayers on gold that are patterned into regions presenting the Arg-Gly-Asp peptide cell adhesion ligand. The patterned regions differ in the electrochemical properties of the linkers that tether the peptides to the monolayer. In this work, three distinct chemistries are employed that provide for release of the ligand on application of a negative potential, release of the ligand on application of a positive potential, and no change in response to a potential. Cells were allowed to attach to a monolayer patterned into circular regions comprising the three chemistries. Treatment with electric potentials of 650 or -650 mV resulted in the selective release of adherent cells only from regions that display the relevant electroactive groups. This example establishes the preparation of dynamic substrates with multiple functions and will be important to preparing model cultures derived from multiple cell types, with control over the temporal interactions of each cell population.