Nanotechnology-based photodynamic therapy for neovascular disease using a supramolecular nanocarrier loaded with a dendritic photosensitizer

Light-responsive polymeric nanoparticles for retinal drug delivery: design cues, challenges and future perspectives

A multitude of sight-threatening retinal diseases, affecting hundreds of millions around the globe, lack effective pharmacological treatments due to ocular barriers and common drug delivery limitations. Polymeric nanoparticles (PNPs) are versatile drug carriers with sustained drug release profiles and tunable physicochemical properties which have been explored for ocular drug delivery to both anterior and posterior ocular tissues. PNPs can incorporate a wide range of drugs and overcome the challenges of conventional retinal drug delivery. Moreover, PNPs can be engineered to respond to specific stimuli such as ultraviolet, visible, or near-infrared light, and allow precise spatiotemporal control of the drug release, enabling tailored treatment regimens and reducing the number of required administrations. The objective of this study is to emphasize the therapeutic potential of light-triggered drug-loaded polymeric nanoparticles to treat retinal diseases through an exploration of ocular pathologies, challenges in drug delivery, current production methodologies and recent applications. Despite challenges, light-responsive PNPs hold the promise of substantially enhancing the treatment landscape for ocular diseases, aiming for an improved quality of life for patients.

Advanced Technologies of Drug Delivery to the Posterior Eye Segment Targeting Angiogenesis and Ocular Cancer

Retinoblastoma (RB), a childhood retinal cancer is caused due to RB1 gene mutation which affects the child below 5 years of age. Angiogenesis has been proven its role in RB metastasis due to the presence of vascular endothelial growth factor (VEGF) in RB cells. Therefore, exploring angiogenic pathway by inhibiting VEGF in treating RB would pave the way for future treatment. In preclinical studies, anti-VEGF molecule have shown their efficacy in treating RB. However, treatment requires recurrent intra-vitreal injections causing various side effects along with patient nonadherence. As a result, delivery of anti-VEGF agent to retina requires an ocular delivery system that can transport it in a non-invasive manner to achieve patient compliance. Moreover, development of these type of systems are challenging due to the complicated physiological barriers of eye. Adopting a non-invasive or minimally invasive approach for delivery of anti-VEGF agents would not only address the bioavailability issues but also improve patient adherence to therapy overcoming the side effects associated with invasive approach. The present review focuses on the eye cancer, angiogenesis and various novel ocular drug delivery systems that can facilitate inhibition of VEGF in the posterior eye segment by overcoming the eye barriers.

Stages, pathogenesis, clinical management and advancements in therapies of age-related macular degeneration

Age-related macular degeneration (AMD) is a retinal degenerative disorder prevalent in the elderly population, which leads to the loss of central vision. The disease progression can be managed, if not prevented, either by blocking neovascularization ("wet" form of AMD) or by preserving retinal pigment epithelium and photoreceptor cells ("dry" form of AMD). Although current therapeutic modalities are moderately successful in delaying the progression and management of the disease, advances over the past years in regenerative medicine using iPSC, embryonic stem cells, advanced materials (including nanomaterials) and organ bio-printing show great prospects in restoring vision and efficient management of either forms of AMD. This review focuses on the molecular mechanism of the disease, model systems (both cellular and animal) used in studying AMD, the list of various regenerative therapies and the current treatments available. The article also highlights on the recent clinical trials using regenerative therapies and management of the disease.

Peptide Nanofiber System for Sustained Delivery of Anti-VEGF Proteins to the Eye Vitreous

Ranibizumab is a recombinant VEGF-A antibody used to treat the wet form of age-related macular degeneration. It is intravitreally administered to ocular compartments, and the treatment requires frequent injections, which may cause complications and patient discomfort. To reduce the number of injections, alternative treatment strategies based on relatively non-invasive ranibizumab delivery are desired for more effective and sustained release in the eye vitreous than the current clinical practice. Here, we present self-assembled hydrogels composed of peptide amphiphile molecules for the sustained release of ranibizumab, enabling local high-dose treatment. Peptide amphiphile molecules self-assemble into biodegradable supramolecular filaments in the presence of electrolytes without the need for a curing agent and enable ease of use due to their injectable nature-a feature provided by shear thinning properties. In this study, the release profile of ranibizumab was evaluated by using different peptide-based hydrogels at varying concentrations for improved treatment of the wet form of age-related macular degeneration. We observed that the slow release of ranibizumab from the hydrogel system follows extended- and sustainable release patterns without any dose dumping. Moreover, the released drug was biologically functional and effective in blocking the angiogenesis of human endothelial cells in a dose-dependent manner. In addition, an in vivo study shows that the drug released from the hydrogel nanofiber system can stay in the rabbit eye's posterior chamber for longer than a control group that received only a drug injection. The tunable physiochemical characteristics, injectable nature, and biodegradable and biocompatible features of the peptide-based hydrogel nanofiber show that this delivery system has promising potential for intravitreal anti-VEGF drug delivery in clinics to treat the wet form age-related macular degeneration.

Polymer- and lipid-based nanocarriers for ocular drug delivery: Current status and future perspectives

Ocular diseases seriously affect patients' vision and life quality, with a global morbidity of over 43 million blindness. However, efficient drug delivery to treat ocular diseases, particularly intraocular disorders, remains a huge challenge due to multiple ocular barriers that significantly affect the ultimate therapeutic efficacy of drugs. Recent advances in nanocarrier technology offer a promising opportunity to overcome these barriers by providing enhanced penetration, increased retention, improved solubility, reduced toxicity, prolonged release, and targeted delivery of the loaded drug to the eyes. This review primarily provides an overview of the progress and contemporary applications of nanocarriers, mainly polymer- and lipid-based nanocarriers, in treating various eye diseases, highlighting their value in achieving efficient ocular drug delivery. Additionally, the review covers the ocular barriers and administration routes, as well as the prospective future developments and challenges in the field of nanocarriers for treating ocular diseases.

Light-responsive biomaterials for ocular drug delivery

Light-responsive biomaterials can be used for the delivery of therapeutic drugs and nucleic acids, where the tunable/precise delivery of payload highlights the potential of such biomaterials for treating a variety of conditions. The translucency of eyes and advances of laser technology in ophthalmology make light-responsive delivery of drugs feasible. Importantly, light can be applied in a non-invasive fashion; therefore, light-triggered drug delivery systems have great potential for clinical impact. This review will examine various types of light-responsive polymers and the chemistry that underpins their application as ophthalmic drug delivery systems.

A composite System Combining Self-Targeted Carbon Dots and Thermosensitive Hydrogels for Challenging Ocular Drug Delivery

We developed a composite system combining self-targeted carbon dots and thermosensitive in situ hydrogels for ocular drug delivery of diclofenac sodium (DS). DS-CD_C-HP nanoparticles were prepared by loading DS on the surface of CD_C-HP via electrostatic interactions. An orthogonal experimental design was selected to screen the optimal thermosensitive hydrogel matrices and then DS-CD_C-HP nanoparticles were embedded to form the composite system. The physicochemical properties and release behavior of this system were characterized, and in vivo fluorescence imaging was carried out. Corneal penetrability and in vitro cellular studies (cytotoxicity, cell imaging and cell uptake) were performed to test the feasibility and potential of this ocular delivery system. Finally, the optimal gel matrix consisting of Poloxamer 407: Poloxamer 188: HPMC E50 was 21:1:1 (w/v %), and the gelation temperature before adding artificial tear fluid was 26.67°C and 34.29°C, respectively. This system has the characteristics of biphasic drug release. In addition, the corneal penetrability and in vivo fluorescence study indicated that corneal transmittance was enhanced and drug retention time was extended. Cellular studies revealed that the DS-CD_C-HP-Gel has good cytocompatibility and CD44 targeting. In summary, this composite system combines carbon dots with hydrogels, offering new potential for ocular drug delivery.

Bioinspired Applications of Porphyrin Derivatives

Porphyrin derivatives are ubiquitous in nature and have important biological roles, such as in light harvesting, oxygen transport, and catalysis. Owing to their intrinsic π-conjugated structure, porphyrin derivatives exhibit characteristic photophysical and electrochemical properties. In biological systems, porphyrin derivatives are associated with various protein molecules through noncovalent interactions. For example, hemoglobin, which is responsible for oxygen transport in most vertebrates, consists of four subunits of a globular protein with an iron porphyrin derivative prosthetic group. Furthermore, noncovalently arranged porphyrin derivatives are the fundamental chromophores in light-harvesting systems for photosynthesis in plants and algae. These biologically important roles originate from the functional versatility of porphyrin derivatives. Specifically, porphyrins are excellent host compounds, forming coordination complexes with various metal ions that adds functionality to the porphyrin unit, such as redox activity and additional ligand binding at the central metal ion. In addition, porphyrins are useful building blocks for functional supramolecular assemblies because of their flat and symmetrical molecular architectures, and their excellent photophysical properties are typically utilized for the fabrication of bioactive functional materials. In this Account, we summarize our endeavors over the past decade to develop functional materials based on porphyrin derivatives using bioinspired approaches. In the first section, we discuss several synthetic receptors that act as artificial allosteric host systems and can be used for the selective detection of various chemicals, such as cyanide, chloride, and amino acids. In the second section, we introduce multiporphyrin arrays as mimics of natural light-harvesting complexes. The active control of energy transfer processes by additional guest binding and the fabrication of organic photovoltaic devices using porphyrin derivatives are also introduced. In the third section, we introduce several types of porphyrin-based supramolecular assemblies. Through noncovalent interactions such as metal-ligand interaction, hydrogen bonding, and π-π interaction, porphyrin derivatives were constructed as supramolecular polymers with formation of fiber or toroidal assembly. In the last section, the application of porphyrin derivatives for biomedical nanodevice fabrication is introduced. Even though porphyrins were good candidates as photosensitizers for photodynamic therapy, they have limitations for biomedical application owing to aggregation in aqueous media. We suggested ionic dendrimer porphyrins and they showed excellent photodynamic therapy (PDT) efficacy.

Carbon Dot Nanoparticles: Exploring the Potential Use for Gene Delivery in Ophthalmic Diseases

Ocular gene therapy offers significant potential for preventing retinal dystrophy in patients with inherited retinal dystrophies (IRD). Adeno-associated virus (AAV) based gene transfer is the most common and successful gene delivery approach to the eye. These days, many studies are using non-viral nanoparticles (NPs) as an alternative therapeutic option because of their unique properties and biocompatibility. Here, we discuss the potential of carbon dots (CDs), a new type of nanocarrier for gene delivery to the retinal cells. The unique physicochemical properties of CDs (such as optical, electronic, and catalytic) make them suitable for biosensing, imaging, drug, and gene delivery applications. Efficient gene delivery to the retinal cells using CDs depends on various factors, such as photoluminescence, quantum yield, biocompatibility, size, and shape. In this review, we focused on different approaches used to synthesize CDs, classify CDs, various pathways for the intake of gene-loaded carbon nanoparticles inside the cell, and multiple studies that worked on transferring nucleic acid in the eye using CDs.

Photo-Based Nanomedicines Using Polymeric Systems in the Field of Cancer Imaging and Therapy

The use of photo-based nanomedicine in imaging and therapy has grown rapidly. The property of light in converting its energy into different forms has been exploited in the fields of optical imaging (OI) and phototherapy (PT) for diagnostic and therapeutic applications. The development of nanotechnology offers numerous advantages to overcome the challenges of OI and PT. Accordingly, in this review, we shed light on common photosensitive agents (PSAs) used in OI and PT; these include fluorescent and bioluminescent PSAs for OI or PT agents for photodynamic therapy (PDT) and photothermal therapy (PTT). We also describe photo-based nanotechnology systems that can be used in photo-based diagnostics and therapies by using various polymeric systems.

NIR Photoregulated Theranostic System Based on Hexagonal-Phase Upconverting Nanoparticles for Tumor-Targeted Photodynamic Therapy and Fluorescence Imaging

Although photodynamic therapy (PDT) is an effective, minimally invasive therapeutic modality with advantages in highly localized and specific tumor treatments, large and deep-seated cancers within the body cannot be successfully treated due to low transparency to visible light. To improve the therapeutic efficiency of tumor treatment in deep tissue and reduce the side effects in normal tissue, this study developed a near-infrared (NIR)-triggered upconversion nanoparticle (UCNP)-based photosensitizer (PS) carrier as a new theranostics system. The NaYF4:Yb/Er UCNPs were synthesized by a hydrothermal method, producing nanoparticles of a uniformly small size (≈20 nm) and crystalline morphology of the hexagonal phase. These UCNPs were modified with folic acid-conjugated biocompatible block copolymers through a bidentate dihydrolipoic acid linker. The polymer modified hexagonal phase UCNPs (FA-PEAH-UCNPs) showed an improved dispersibility in the aqueous solution and strong NIR-to-vis upconversion fluorescence. The hydrophobic PS, pheophorbide a (Pha), was then conjugated to the stable vectors. Moreover, these UCNP-based Pha carriers containing tumor targeting folic acid ligands exhibited the significantly enhanced cellular uptake efficiency as well as PDT treatment efficiency. These results suggested that this system could extend the excitation wavelength of PDT to the NIR region and effectively improve therapeutic efficiency of PSs.

Nanoformulations for Ocular Delivery of Drugs - A Patent Perspective

Efficient delivery of ocular therapeutics with improved efficacy, enhanced bioavailability, and acceptable patient compliance presents unique challenges. This can be attributed to the presence of protective mechanisms, physicobiological barriers, and structural obstacles in the eye. Nanotherapeutic interventions have been explored extensively over the past few years to overcome these limitations. The present review focusses on the nanoformulations developed for the diagnosis and treatment of various ocular diseases besides providing an in-depth insight into the patents reported for the same.

Tuning surface functionalities of sub-10 nm-sized nanocarriers to target outer retina in designing drug delivery agents for intravitreal administration

Age-related macular degeneration (AMD) is one of the leading causes of irreversible blindness, generally affecting people over 50 years of age in industrialized countries. Despite the effectiveness of anti-vascular endothelial growth factor (VEGF) therapy in attenuating the growth of new blood vessels, substantial visual improvements are rare with this complex disease. Furthermore, the current regimen of repeated monthly intravitreal injections of drugs can result in serious side effects. Combination therapies-to complement anti-VEGF alone-with a prolonged therapeutic effect and efficient delivery to the intended site are urgently needed, which could be realized through the use of carefully designed nanocarriers. To understand the physicochemical effects (e.g., size, charge, geometry) of intravitreally administered nanocarriers on their bioavailability, distribution, and targeting efficiency across multiple layers of the retina, here we prepared seven different types of surface-functionalized water-soluble dendritic nanocarriers with hydrodynamic sizes mostly under 5 nm. A similar stoichiometric amount of fluorophore was covalently attached to each of these biocompatible nanocarriers for quantitative analyses by confocal microscopy of cryosectioned healthy mouse eyes. Interestingly, at 24 h post-injection, the nanocarrier with multiple copies of glucosamine on the surface (D_NSG) accumulated predominantly in the photoreceptor layer and the retinal pigment epithelium (RPE), which are speculated to be associated with AMD pathogenesis (i.e., target sites). Furthermore, extended residence at these outer retinal layers was demonstrated by D_NSG, which appeared to gradually turn into micron-scale particles potentially through aggregation. Our systematic findings may provide useful guidelines for the rational design of intravitreal nanocarriers to treat vision-threatening retinal diseases, including AMD.

Porphyrin Nanocage-Embedded Single-Molecular Nanoparticles for Cancer Nanotheranostics

Single molecular nanoparticles (SMNPs) integrating imaging and therapeutic capabilities exhibit unparalleled advantages in cancer theranostics, ranging from excellent biocompatibility, high stability, prolonged blood lifetime to abundant tumor accumulation. Herein, we synthesize a sophisticated porphyrin nanocage that is further functionalized with twelve polyethylene glycol arms to prepare SMNPs (porSMNPs). The porphyrin nanocage embedded in porSMNPs can be utilized as a theranostic platform. PET imaging allows dynamic observation of the bio-distribution of porSMNPs, confirming their excellent circulation time and preferential accumulation at the tumor site, which is attributed to the enhanced permeability and retention effect. Moreover, the cage structure significantly promotes the photosensitizing effect of porSMNs by inhibiting the π-π stacking interactions of the photosensitizers, ablating of the tumors without relapse by taking advantage of photodynamic therapy.

Poly(photosensitizer) Nanoparticles for Enhanced in Vivo Photodynamic Therapy by Interrupting the π-π Stacking and Extending Circulation Time

The natural planar and rigid structures of most of the hydrophobic photosensitizers (PSs) [such as tetraphenyl porphyrin (TPP)] significantly reduce their loading efficiencies in polymeric nanoparticles (NPs) because of the strong π-π interaction-induced aggregation. This aggregation-caused quenching will further reduce the quantum yield of singlet oxygen (¹O₂) generation and weaken the efficiency of photodynamic therapy (PDT). In addition, the small molecular PSs exhibit short tumor retention time and tend to be easily cleared once released. Herein, poly(TPP) NPs, prepared by cross-linking of reactive oxygen species degradable, thioketal linkers and TPP derivatives, followed by coprecipitation, were first developed with quantitative loading efficiency (>99%), uniform NP sizes (without aggregation), increased singlet oxygen quantum yield (Φ_Δ = 0.79 in dimethyl sulfoxide compared with 0.52 for original TPP), increased in vitro phototoxicity, extended tumor retention time, light-triggered on-demand release, and enhanced in vivo antitumor efficacy, which comprehensively address the multiple issues for most of the PSs in the PDT area.

Ocular Drug Delivery

Although the eye is an accessible organ for direct drug application, ocular drug delivery remains a major challenge due to multiple barriers within the eye. Key barriers include static barriers imposed by the cornea, conjunctiva, and retinal pigment epithelium and dynamic barriers including tear turnover and blood and lymphatic clearance mechanisms. Systemic administration by oral and parenteral routes is limited by static blood-tissue barriers that include epithelial and endothelial layers, in addition to rapid vascular clearance mechanisms. Together, the static and dynamic barriers limit the rate and extent of drug delivery to the eye. Thus, there is an ongoing need to identify novel delivery systems and approaches to enhance and sustain ocular drug delivery. This chapter summarizes current and recent experimental approaches for drug delivery to the anterior and posterior segments of the eye.

Stimuli responsive PEGylated bismuth selenide hollow nanocapsules for fluorescence/CT imaging and light-driven multimodal tumor therapy

PEGylated bismuth selenide hollow nanocapsules encapsulating doxorubicin and chlorin e6 for fluorescence/CT imaging and light-driven multimodal tumor therapy.

2D amphiphilic organoplatinum(ii) metallacycles: their syntheses, self-assembly in water and potential application in photodynamic therapy

Two 2D amphiphilic organoplatinum(ii) metallacycles with a porphyrin unit as the core and hydrophilic glycol units as the tail were designed and fabricated successfully through a new method called "coordination-driven self-assembly". They can self-assemble into micelles in water and have potential applications in photodynamic therapy.

Block Copolymer Micelles in Nanomedicine Applications

Polymeric micelles are demonstrating high potential as nanomedicines capable of controlling the distribution and function of loaded bioactive agents in the body, effectively overcoming biological barriers, and various formulations are engaged in intensive preclinical and clinical testing. This Review focuses on polymeric micelles assembled through multimolecular interactions between block copolymers and the loaded drugs, proteins, or nucleic acids as translationable nanomedicines. The aspects involved in the design of successful micellar carriers are described in detail on the basis of the type of polymer/payload interaction, as well as the interplay of micelles with the biological interface, emphasizing on the chemistry and engineering of the block copolymers. By shaping these features, polymeric micelles have been propitious for delivering a wide range of therapeutics through effective sensing of targets in the body and adjustment of their properties in response to particular stimuli, modulating the activity of the loaded drugs at the targeted sites, even at the subcellular level. Finally, the future perspectives and imminent challenges for polymeric micelles as nanomedicines are discussed, anticipating to spur further innovations.

Synthesis and Characterization of Temperature-Sensitive and Chemically Cross-Linked Poly( N-isopropylacrylamide)/Photosensitizer Hydrogels for Applications in Photodynamic Therapy

A novel poly( N-isopropylacrylamide) (PNIPAM) hydrogel containing different photosensitizers (protoporphyrin IX (PpIX), pheophorbide a (Pba), and protoporphyrin IX dimethyl ester (PpIX-DME)) has been synthesized with a significant improvement in water solubility and potential for PDT applications compared to the individual photosensitizers (PSs). Conjugation of PpIX, Pba, and PpIX-DME to the poly( N-isopropylacrylamide) chain was achieved using the dispersion polymerization method. This study describes how the use of nanohydrogel structures to deliver a photosensitizer with low water solubility and high aggregation tendencies in polar solvents overcomes these limitations. FT-IR spectroscopy, UV-vis spectroscopy, ¹H NMR, fluorescence spectroscopy, SEM, and DLS analysis were used to characterize the PNIPAM-photosensitizer nanohydrogels. Spectroscopic studies indicate that the PpIX, Pba, and PpIX-DME photosensitizers are covalently conjugated to the polymer chains, which prevents aggregation and thus allows significant singlet oxygen production upon illumination. Likewise, the lower critical solution temperature was raised to ∼44 °C in the new PNIPAM-PS hydrogels. The PNIPAM hydrogels are biocompatible with >90% cell viability even at high concentrations of the photosensitizer in vitro. Furthermore, a very sharp onset of light-dependent toxicity for the PpIX-based nanohydrogel in the nanomolar range and a more modest, but significant, photocytotoxic response for Pba-PNIPAM and PpIX-DME-PNIPAM nanohydrogels suggest that the new hydrogels have potential for applications in photodynamic therapy.

Water-soluble porphyrin-PAMAM-conjugates of melphalan and their anticancer activity

p-[bis(chloro-2-ethyl)amino]-L-phenylalanine (melphalan) is an approved anti-cancer agent with a broad spectrum of antitumor activity. However, it has some disadvantages, such as poor water-solubility followed by rapid elimination, which reduce the target specificity. To solve these problems, porphyrin- poly(amidoamine) or PAMAM-conjugates of melphalan were synthesized and characterized. The dendrimeric conjugates showed satisfactory water solubility. It was found that the size of the dendrimer played a crucial role in controlling the drug content and diameter of the melphalan-conjugates. The in vitro studies of cell cytotoxicity revealed that by employing the dendrimeric conjugation strategy and using the PAMAM dendritic arms as spacers, the conjugates had good anti-cancer activity and lower toxicity than free melphalan.

Polyion complex micelle formed from tetraphenylethene containing block copolymer

BACKGROUND

Polymeric micelles attract great attention in drug delivery and therapeutics. Various types of block copolymers have been designed for the application in biomedical fields. If we can introduce additional functional groups to the block copolymers, we can achieve advanced applications. In this regards, we tried to introduce aggregation induced emission enhancement (AIE) unit in the block copolymer.

METHODS

The formation of polyion complex micelle was confirmed by dynamic light scattering and transmission electron microscopy. HeLa cells were incubated with polyion complex micelle and broad-band visible light using a halogen lamp (150 W) was irradiated to evaluate photocytotoxicity of polyion complex (PIC) micelle.

RESULTS

For the design of functional polymeric micelle, aggregation induced emission enhancement unit was introduced in the middle of block copolymer. We newly synthesized a new type block copolymer (PEG-TPE-PEI) possessing tetraphenylethene (TPE) group, as an AIE unit, in the middle of polymeric segments of PEG and PEI, which successfully formed PIC micelle with DP. The formation of PIC micelle was confirmed by dynamic light scattering, ζ potential measurement and transmission electron microscopy.

CONCLUSIONS

PEG-TPE-PEI successfully formed PIC micelle by mixing with negatively charged dendrimer porphyrin. The PIC micelle exhibited photocytotoxicity upon illumination of broadband visible light.

Nanotechnology-based strategies for treatment of ocular disease

Ocular diseases include various anterior and posterior segment diseases. Due to the unique anatomy and physiology of the eye, efficient ocular drug delivery is a great challenge to researchers and pharmacologists. Although there are conventional noninvasive and invasive treatments, such as eye drops, injections and implants, the current treatments either suffer from low bioavailability or severe adverse ocular effects. Alternatively, the emerging nanoscience and nanotechnology are playing an important role in the development of novel strategies for ocular disease therapy. Various active molecules have been designed to associate with nanocarriers to overcome ocular barriers and intimately interact with specific ocular tissues. In this review, we highlight the recent attempts of nanotechnology-based systems for imaging and treating ocular diseases, such as corneal d iseases, glaucoma, retina diseases, and choroid diseases. Although additional work remains, the progress described herein may pave the way to new, highly effective and important ocular nanomedicines.

Biocompatible Polyion Complex Micelles Synthesized from Arborescent Polymers

Water-dispersible polyion complex (PIC) micelles were prepared by the self-assembly of an arborescent polystyrene-graft-poly(2-vinylpyridine) copolymer (denoted G0PS-g-P2VP or G1) serving as core and a poly(acrylic acid)-block-poly(2-hydroxyethyl acrylate) (PAA-b-PHEA) double-hydrophilic block copolymer (DHBC) forming a shell. Varying the density of hydrophilic polymer chains in the stabilizing layer provided control over the size and structure of the entities obtained, from large flocculated species to stable isolated PIC micelles with diameters ranging from 42 to 67 nm. The hydrodynamic radius (determined from dynamic light scattering measurements), and the weight-average molar mass (M̅_w) and radius of gyration of the scatterers (extracted from static multiangle light scattering data) evidenced the formation of either isolated or aggregated PIC micelles depending on the self-assembly conditions used (pH, concentration and mixing molar ratio f). Changes in the morphology of the arborescent copolymer after complexation were observed by atomic force microscopy (AFM) imaging. In particular, by varying the force applied with the AFM tip on the samples, the core-shell structure of the PIC micelles was clearly evidenced. The PIC micelles displayed no significant cytotoxicity toward mouse fibroblast L929 cells, a standard cell line recommended for toxicity assays, due to the good biocompatibility of the hydrophilic PAA-b-PHEA shell. In spite of a negative residual zeta potential due to an excess of negative charges, fluorescently labeled PIC* micelles were successfully internalized by L929 cells, as confirmed by laser scanning confocal microscopy (LSCM) and transmission electron microscopy (TEM).

Perspectives on: Materials Aspects for Retinal Prostheses

Retinitis pigmentosa and age-related macular degeneration are both incurable eye diseases that lead to blindness due to photoreceptor degeneration. Electrically stimulating the remaining intact nerve cells may generate some useful vision for patients afflicted with these diseases. Various types of retinal prostheses, sub- and epi-retinal electrode arrays, as well as subretinal microphotodiode arrays are considered from a materials and biocompatibility point of view. Other, more innovative approaches to restoring vision, such as microfluidic pumps and activated nanosystems that deliver neurotransmitters in a controlled way and photodynamic therapy are being developed. This article discusses materials aspects of retinal prostheses that are currently in use or under development.

Dendrimer porphyrin-coated gold nanoshells for the synergistic combination of photodynamic and photothermal therapy

A dendrimer porphyrin (DP)-coated gold nanoshell (AuNS-DP) was prepared for the synergistic combination of photodyanmic and photothermal therapy.

Effectiveness of the Photoactive Dye Methylene Blue versus Caspofungin on the Candida parapsilosis Biofilm in vitro and ex vivo

This research studied the effectiveness of the photoactive compound methylene blue (MB) activated with red LED light (576-672 nm) compared to that of caspofungin (CAS) on 1 Candida albicans and 3 Candida parapsilosis strains. Results were evaluated in terms of SMIC50 for CAS or in PDI (photodynamic inactivation)-SMIC50 for MB (minimal inhibitory concentration inhibiting sessile biofilm to 50% in comparison to the control without CAS or after irradiation in comparison to the control without MB). While all strains were susceptible to CAS in planktonic form, the SMIC50 was determined to be >16 μg mL(-1) when CAS was added to a 24 h biofilm. However, PDI-MIC50s (1.67 mW cm(-2) , fluence 15 J cm(-2) ) were 0.0075-0.03 mmol L(-1) . For biofilm, PDI-SMIC50s were in the range from 0.7 to 1.35 mmol L(-1) . MB concentration of 1 mmol L(-1) prevented a biofilm being formed ex vivo on mouse tongues after irradiation regardless of the application time, in contrast to CAS, which was only effective at a concentration of 16 μg mL(-1) when it was added at the beginning of biofilm formation. PDI seems to be a promising method for the prevention of microbial biofilms that do not respond significantly to conventional drugs.

Photodynamic therapy: one step ahead with self-assembled nanoparticles

Photodynamic therapy (PDT) is a promising treatment modality for cancer with possible advantages over current treatment alternatives. It involves combination of light and a photosensitizer (PS), which is activated by absorption of specific wavelength light and creates local tissue damage through generation of reactive oxygen species (ROS) that induce a cascade of cellular and molecular events. However, as of today, PDT is still in need of improvement and nanotechnology may play a role. PDT frequently employs PS with molecular structures that are highly hydrophobic, water insoluble and prone to aggregation. Aggregation of PS leads to reduced ROS generation and thus lowers the PDT activity. Some PS such as 5-aminolevulinic acid (ALA) cannot penetrate through the stratum corneum of the skin and systemic administration is not an option due to frequently encountered side effects. Therefore PS are often encapsulated or conjugated in/on nano-drug delivery vehicles to allow them to be better taken up by cells and to more selectively deliver them to tumors or other target tissues. Several nano-drug delivery vehicles including liposomes, fullerosomes and nanocells have been tested and reviewed. Here we cover non-liposomal self-assembled nanoparticles consisting of polymeric micelles including block co-polymers, polymeric micelles, dendrimers and porphysomes.

Direct observation of key photoinduced dynamics in a potential nano-delivery vehicle of cancer drugs

The crucial photoinduced dynamics in ZnO nanoparticles (NPs) upon complexation with the cancer drug protoporphyrin IX (PP).

Photodynamic tumor therapy of nanoparticles with chlorin e6 sown in poly(ethylene glycol) forester

We developed novel photosensitizing drug-carrying nanoparticles with poly(ethylene glycol) (PEG) forester.

Strategies for delivering porphyrinoid-based photosensitizers in therapeutic applications

Delivery strategies for porphyrinoid-based photosensitizers for use in therapeutic applications are based on a myriad of factors, which include porphyrinoid structure, solubility and cellular targets. These drug-delivery methods include encapsulation, hydrogels, protein carriers, nanoparticles and polymeric micelles among others. This article reviews the strategies for delivering porphyrinoids published to date and will focus on porphyrins, corroles, chlorins, bacteriochlorins, porphyrazines and phthalocyanines. Highlighted are the most recent and different strategies used for each of the corresponding porphyrinoid-based macrocycles.

NIR excitation of upconversion nanohybrids containing a surface grafted Bodipy induces oxygen-mediated cancer cell death

We report the preparation of water-dispersible, ca. 30 nm-sized nanohybrids containing NaYF₄:Er³⁺, Yb³⁺ up-conversion nanoparticles (UCNPs), capped with a polyethylene glycol (PEG) derivative and highly loaded with a singlet oxygen photosensitizer, specifically a diiodo-substituted Bodipy (IBDP). The photosensitizer, bearing a carboxylic group, was anchored to the UCNP surface and, at the same time, embedded in the PEG capping; the combined action of the UCNP surface and PEG facilitated the loading for an effective energy transfer and, additionally, avoided photosensitizer leaching from the nanohybrid (UCNP-IBDP@PEG). The effectiveness of the nanohybrids in generating singlet oxygen after near-infrared (NIR) excitation (975 nm) with a continuous wavelength (CW) laser was evidenced by using a probe molecule. In vitro assays demonstrated that the UCNP-IBDP@PEG nanohybrid was taken up by the SH-SY5Y human neuroblastoma-derived cells showing low cytotoxicity. Moreover, ca. 50% cancer cell death was observed after NIR irradiation (45 min, 239 mW).