Verteporfin

Biotechnology and Biomaterial-Based Therapeutic Strategies for Age-Related Macular Degeneration. Part I: Biomaterials-Based Drug Delivery Devices

Age-related Macular Degeneration (AMD) is an up-to-date untreatable chronic neurodegenerative eye disease of multifactorial origin, and the main causes of blindness in over 65 years old people. It is characterized by a slow progression and the presence of a multitude of factors, highlighting those related to diet, genetic heritage and environmental conditions, present throughout each of the stages of the illness. Current therapeutic approaches, mainly consisting of intraocular drug delivery, are only used for symptoms relief and/or to decelerate the progression of the disease. Furthermore, they are overly simplistic and ignore the complexity of the disease and the enormous differences in the symptomatology between patients. Due to the wide impact of the AMD and the up-to-date absence of clinical solutions, the development of biomaterials-based approaches for a personalized and controlled delivery of therapeutic drugs and biomolecules represents the main challenge for the defeat of this neurodegenerative disease. Here we present a critical review of the available and under development AMD therapeutic approaches, from a biomaterials and biotechnological point of view. We highlight benefits and limitations and we forecast forthcoming alternatives based on novel biomaterials and biotechnology methods. In the first part we expose the physiological and clinical aspects of the disease, focusing on the multiple factors that give origin to the disorder and highlighting the contribution of these factors to the triggering of each step of the disease. Then we analyze available and under development biomaterials-based drug-delivery devices (DDD), taking into account the anatomical and functional characteristics of the healthy and ill retinal tissue.

Light-triggered switching of liposome surface charge directs delivery of membrane impermeable payloads in vivo

Surface charge plays a fundamental role in determining the fate of a nanoparticle, and any encapsulated contents, in vivo. Herein, we describe, and visualise in real time, light-triggered switching of liposome surface charge, from neutral to cationic, in situ and in vivo (embryonic zebrafish). Prior to light activation, intravenously administered liposomes, composed of just two lipid reagents, freely circulate and successfully evade innate immune cells present in the fish. Upon in situ irradiation and surface charge switching, however, liposomes rapidly adsorb to, and are taken up by, endothelial cells and/or are phagocytosed by blood resident macrophages. Coupling complete external control of nanoparticle targeting together with the intracellular delivery of encapsulated (and membrane impermeable) cargos, these compositionally simple liposomes are proof that advanced nanoparticle function in vivo does not require increased design complexity but rather a thorough understanding of the fundamental nano-bio interactions involved.

Regulation of the Ocular Cell/Tissue Response by Implantable Biomaterials and Drug Delivery Systems

Therapeutic advancements in the treatment of various ocular diseases is often linked to the development of efficient drug delivery systems (DDSs), which would allow a sustained release while maintaining therapeutic drug levels in the target tissues. In this way, ocular tissue/cell response can be properly modulated and designed in order to produce a therapeutic effect. An ideal ocular DDS should encapsulate and release the appropriate drug concentration to the target tissue (therapeutic but non-toxic level) while preserving drug functionality. Furthermore, a constant release is usually preferred, keeping the initial burst to a minimum. Different materials are used, modified, and combined in order to achieve a sustained drug release in both the anterior and posterior segments of the eye. After giving a picture of the different strategies adopted for ocular drug release, this review article provides an overview of the biomaterials that are used as drug carriers in the eye, including micro- and nanospheres, liposomes, hydrogels, and multi-material implants; the advantages and limitations of these DDSs are discussed in reference to the major ocular applications.

Nanocarriers for the Delivery of Medical, Veterinary, and Agricultural Active Ingredients

Nanocarrier-based delivery systems can be used to increase the safety and efficacy of active ingredients in medical, veterinary, or agricultural applications, particularly when such ingredients are unstable, sparingly soluble, or cause off-target effects. In this review, we highlight the diversity of nanocarrier materials and their key advantages compared to free active ingredients. We discuss current trends based on peer-reviewed research articles, patent applications, clinical trials, and the nanocarrier formulations already approved by regulatory bodies. Although most nanocarriers have been engineered to combat cancer, the number of formulations developed for other purposes is growing rapidly, especially those for the treatment of infectious diseases and parasites affecting humans, livestock, and companion animals. The regulation and prohibition of many pesticides have also fueled research to develop targeted pesticide delivery systems based on nanocarriers, which maximize efficacy while minimizing the environmental impact of agrochemicals.

Trends and targets in antiviral phototherapy

Photodynamic therapy (PDT) is a well-established treatment option in the treatment of certain cancerous and pre-cancerous lesions. Though best-known for its application in tumor therapy, historically the photodynamic effect was first demonstrated against bacteria at the beginning of the 20^th century. Today, in light of spreading antibiotic resistance and the rise of new infections, this photodynamic inactivation (PDI) of microbes, such as bacteria, fungi, and viruses, is gaining considerable attention. This review focuses on the PDI of viruses as an alternative treatment in antiviral therapy, but also as a means of viral decontamination, covering mainly the literature of the last decade. The PDI of viruses shares the general action mechanism of photodynamic applications: the irradiation of a dye with light and the subsequent generation of reactive oxygen species (ROS) which are the effective phototoxic agents damaging virus targets by reacting with viral nucleic acids, lipids and proteins. Interestingly, a light-independent antiviral activity has also been found for some of these dyes. This review covers the compound classes employed in the PDI of viruses and their various areas of use. In the medical area, currently two fields stand out in which the PDI of viruses has found broader application: the purification of blood products and the treatment of human papilloma virus manifestations. However, the PDI of viruses has also found interest in such diverse areas as water and surface decontamination, and biosafety.

The Photosensitising Clinical Agent Verteporfin Is an Inhibitor of SPAK and OSR1 Kinases

STE20/SPS1-related proline/alanine-rich kinase (SPAK) and oxidative-stress-responsive kinase 1 (OSR1) are two serine/threonine protein kinases that play key roles in regulating ion homeostasis. Various SPAK and OSR1 mouse models exhibited reduced blood pressure. Herein, the discovery of verteporfin, a photosensitising agent used in photodynamic therapy, as a potent inhibitor of SPAK and OSR1 kinases is reported. It is shown that verteporfin binds the kinase domains of SPAK and OSR1 and inhibits their catalytic activity in an adenosine triphosphate (ATP)-independent manner. In cells, verteporfin was able to suppress the phosphorylation of the ion co-transporter NKCC1; a downstream physiological substrate of SPAK and OSR1 kinases. Kinase panel screening indicated that verteporfin inhibited a further eight protein kinases more potently than that of SPAK and OSR1. Although verteporfin has largely been studied as a modifier of the Hippo signalling pathway, this work indicates that the WNK-SPAK/OSR1 signalling cascade is also a target of this clinical agent. This finding could explain the fluctuation in blood pressure noted in patients and animals treated with this drug.

Extended ocular drug delivery systems for the anterior and posterior segments: biomaterial options and applications

INTRODUCTION

The development of new therapies for treating various eye conditions has led to a demand for extended release delivery systems, which would lessen the need for frequent application while still achieving therapeutic drug levels in the target tissues. Areas covered: Following an overview of the different ocular drug delivery modalities, this article surveys the biomaterials used to develop sustained release drug delivery systems. Microspheres, nanospheres, liposomes, hydrogels, and composite systems are discussed in terms of their primary materials. The advantages and disadvantages of each drug delivery system are discussed for various applications. Recommendations for modifications and strategies for improvements to these basic systems are also discussed. Expert opinion: An ideal sustained release drug delivery system should be able to encapsulate and deliver the necessary drug to the target tissues at a therapeutic level without any detriment to the drug. Drug encapsulation should be as high as possible to minimize loss and unless it is specifically desired, the initial burst of drug release should be kept to a minimum. By modifying various biomaterials, it is possible to achieve sustained drug delivery to both the anterior and posterior segments of the eye.

Nanotechnology for photodynamic therapy: a perspective from the Laboratory of Dr. Michael R. Hamblin in the Wellman Center for Photomedicine at Massachusetts General Hospital and Harvard Medical School

The research interests of the Hamblin Laboratory are broadly centered on the use of different kinds of light to treat many different diseases. Photodynamic therapy (PDT) uses the combination of dyes with visible light to produce reactive oxygen species and kill bacteria, cancer cells and destroy unwanted tissue. Likewise, UV light is also good at killing especially pathogens. By contrast, red or near-infrared light can have the opposite effect, to act to preserve tissue from dying and can stimulate healing and regeneration. In all these applications, nanotechnology is having an ever-growing impact. In PDT, self-assembled nano-drug carriers (micelles, liposomes, etc.) play a great role in solubilizing the photosensitizers, metal nanoparticles can carry out plasmon resonance enhancement, and fullerenes can act as photosensitizers, themselves. In the realm of healing, single-walled carbon nanotubes can be electrofocused to produce nano-electonic biomedical devices, and nanomaterials will play a great role in restorative dentistry.

Advances in ocular drug delivery: emphasis on the posterior segment

INTRODUCTION

Recent advances in pharmacological therapies to treat ocular diseases such as glaucoma, age-related macular degeneration, diabetic macular edema and retinal vascular occlusions have greatly improved the prognosis for these diseases. Due to these advances in pharmacological therapy, there is a great deal of interest in minimally invasive delivery methods, which has generated rapid developments in the field of ocular drug delivery.

AREAS COVERED

This review will summarize currently available and recent developments for ocular drug delivery to both the anterior and posterior segments. Modes of delivery, including topical, systemic, transcleral/periocular and intravitreal, will be discussed and corresponding examples will be given. This review will highlight the advantages and disadvantages of each mode of delivery and discuss strategies to address these issues.

EXPERT OPINION

An ideal therapy should maintain effective levels of drug for the intended duration of treatment following a single application, yet a significant number of months of therapy may be required. There are numerous approaches under investigation to improve treatment options. From the use of novel biomaterial implants and depots for sustained release, to prodrug formations, to iontophoresis to improve drug delivery, the main emphasis will continue to be placed on less invasive, longer acting, sustained release formulations in the treatment of numerous ocular disorders.

Phototriggerable liposomes: current research and future perspectives

The field of cancer nanomedicine is considered a promising area for improved delivery of bioactive molecules including drugs, pharmaceutical agents and nucleic acids. Among these, drug delivery technology has made discernible progress in recent years and the areas that warrant further focus and consideration towards technological developments have also been recognized. Development of viable methods for on-demand spatial and temporal release of entrapped drugs from the nanocarriers is an arena that is likely to enhance the clinical suitability of drug-loaded nanocarriers. One such approach, which utilizes light as the external stimulus to disrupt and/or destabilize drug-loaded nanoparticles, will be the discussion platform of this article. Although several phototriggerable nanocarriers are currently under development, I will limit this review to the phototriggerable liposomes that have demonstrated promise in the cell culture systems at least (but not the last). The topics covered in this review include (i) a brief summary of various phototriggerable nanocarriers; (ii) an overview of the application of liposomes to deliver payload of photosensitizers and associated technologies; (iii) the design considerations of photoactivable lipid molecules and the chemical considerations and mechanisms of phototriggering of liposomal lipids; (iv) limitations and future directions for in vivo, clinically viable triggered drug delivery approaches and potential novel photoactivation strategies will be discussed.

An experimental study of a modified dahuang zhechong pill on the--angiogenesis of RF/6A cells in vitro

OBJECTIVE

To investigate the effects of a modified Dahuang Zhechong Pill (MDZP) on the angiogenesis of rhesus choroid-retina endothelial (RF/6A) cells and its preliminary mechanism.

METHODS

A 3-(4, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) method was used to assess the effect of a MDZP on RF/6A cell proliferation induced by vascular endothelial growth factor (VEGF). Transwell inserts were used to assess the effect of the MDZP on RF/6A cell migration. Matrigel was used to assess the effect of the MDZP on the tube formation of RF/ 6A cells. Western blotting and quantitative real-time reverse transcription polymerase chain reaction (RT-PCR) were used to detect the protein and mRNA expression, respectively, of VEGF and matrix metalloproteinase-2 (MMP-2) in RF/6A cells treated with the MDZP.

RESULTS

RF/6A cell proliferation induced by VEGF was inhibited by 0.2 mg/mL MDZP. At 0, 12.5, 25 and 50 mg/mL MDZP, the number of cells that migrated through Transwell membranes was 73.33 +/- 4.51, 61.33 +/- 4.04, 28.67 +/- 6.66 and 17.67 +/- 4.16, respectively, and the number of tubes formed in Matrigel was 20.33 +/- 0.58, 13.33 +/- 1.53, 11.00 +/- 1.00 and 1.33 +/- 0.58, respectively. At 100 and 200 mg/mL MDZP, the protein and mRNA expression of VEGF and MMP-2 were inhibited in RF/6A cells. At 400 mg/mL MDZP, the expression of VEGF mRNA and MMP-2 protein were inhibited in RF/6A cells.

CONCLUSIONS

MDZP inhibits the angiogenesis of RF/6A cells via the suppression of proliferation, migration and tube formation of RF/6A cells. Inhibition of the protein and mRNA expression of VEGF and MMP-2 in RF/6A cells may be an important mechanism.

Intravitreal bevacizumab for treatment of subfoveal idiopathic choroidal neovascularization: results of a 1-year prospective trial

PURPOSE

To evaluate the visual and anatomic outcomes of intravitreal bevacizumab in patients with subfoveal idiopathic choroidal neovascularization (CNV).

DESIGN

Prospective, nonrandomized, interventional case series.

METHODS

Forty patients with subfoveal idiopathic CNV were included in this clinical trial. Their eyes were treated with a single intravitreal injection of 1.25 mg bevacizumab followed by as-needed dosing indicated by the presence and recurrence of intraretinal edema, subretinal fluid (SRF), or pigment epithelial detachment (PED), based on optical coherence tomography (OCT) performed monthly. Visual, clinical, angiographic, and anatomic changes were observed over a 12-month follow-up period.

RESULTS

After 12 months of follow-up, the mean logarithm of minimal angle of resolution (logMAR) best-corrected visual acuity (BCVA) improved from 0.53 (20/68 in Snellen equivalent) at baseline to 0.29 (20/39 in Snellen equivalent; P < .001). Mean central retinal thickness determined by OCT decreased from 321 μm to 237 μm (P < .001). All eyes (100%) had stable or improved vision, and 28 eyes (70%) showed an improvement of 2 lines or more. All lesions were in the cicatricial stage of CNV at 12 months of follow-up, with no leakage of fluorescein in the late phase of fluorescein angiography and no intraretinal edema, SRF, and/or PED detected by OCT. No drug-related systemic or ocular side effects were observed.

CONCLUSIONS

Intravitreal bevacizumab is generally well tolerated and improves BCVA in eyes with subfoveal idiopathic CNV over a period of 12 months. Large, randomized, controlled, long-term clinical trials are required to further evaluate the efficacy and optimal strategy of this treatment modality.

Temoporfin (Foscan®, 5,10,15,20-tetra(m-hydroxyphenyl)chlorin)--a second-generation photosensitizer

This review traces the development and study of the second-generation photosensitizer 5,10,15,20-tetra(m-hydroxyphenyl)chlorin through to its acceptance and clinical use in modern photodynamic (cancer) therapy. The literature has been covered up to early 2011.

Photodynamic therapy of idiopathic subfoveal choroidal neovascularization in Taiwanese patients: a 2-year follow-up

AIMS

To study the efficacy of verteporfin photodynamic therapy (VPDT) retrospectively in the treatment of idiopathic subfoveal choroidal neovascularization (ICNV) in an Asian population in correlation with number of treatments and age at treatment. This is the first report to compare the efficacy between single and multiple treatments.

METHODS

VPDT was administered according to protocol to 45 eyes in 45 patients aged 18-55 years diagnosed with active subfoveal ICNV between September 2003 and December 2005. In total 28 patients received a single VPDT treatment and the remaining 17 received multiple treatments. Collected measurements of visual acuity (VA) were plotted on a time-course model, and later dichotomized by age (18-45 vs 46-55 years).

RESULTS

The 28 patients receiving a single VPDT treatment showed significant improvement in VA at 3-month follow-up. The 17 patients, who did not show improvement after the first treatment, received multiple VPDT treatments. Those patients showed an even clearer trend in VA improvement although significance was detected only at the 24th month. All patients showed a significant improvement in mean VA of 0.46 logMAR (P<0.01 compared to baseline) by the end of the 24-month observation period, although VPDT treatment for subfoveal ICNV appears to stabilize vision more rapidly in younger patients.

CONCLUSIONS

ICNV patients who did not benefit from single VPDT treatments could receive multiple treatments, and showed a more significant improvement in visual acuity. These results are the first of their kind in ICNV treatment.