Nanoparticle formulation enhances the delivery and activity of a vascular endothelial growth factor antisense oligonucleotide in human retinal pigment epithelial cells

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.

Nanoparticle Fraught Liposomes: A Platform for Increased Antibiotic Selectivity in Multidrug Resistant Bacteria

Increasing antibiotic concentrations within bacterial cells while reducing them in mammalian ones would ultimately result in an enhancement of antibacterial actions, overcoming multidrug resistance, all while minimizing toxicity. Nanoparticles (NPs) have been used in numerous occasions to overcome antibiotic resistance, poor drug solubility, and stability. However, the concomitant increase in antibiotic concentration in mammalian cells and the resultant toxicity are usually overlooked. Without compromising bacterial cell fusion, large liposomes (Lip) have been reported to show reduced uptake in mammalian cells. Therefore, in this work, small NP fraught liposomes (NP-Lip) were formulated with the aim of increasing NP uptake and antibiotic delivery in bacterial cells but not in mammalian ones. Small polylactic-co-glycolic acid NPs were therefore loaded with erythromycin (Er), an antibiotic with low membrane permeability that is susceptible to drug efflux, and 3c, a 5-cyanothiazolyl urea derivative with low solubility and stability. In vitro experiments demonstrated that the incorporation of small NPs into large Lip resulted in a reduction in NP uptake by HEK293 cells while increasing it in Gram-negative bacteria (Escherichia coli DH5α, E. coli K12, and Pseudomonas aeruginosa), consequently resulting in an enhancement of antibiotic selectivity by fourfold toward E. coli (both strains) and eightfold toward P. aeruginosa. Ocular administration of NP-Lip in a P. aeruginosa keratitis mouse model demonstrated the ability of Er/3c-loaded NP-Lip to result in a complete recovery. More importantly, in comparison to NPs, the ocular administration of NP-Lip showed a reduction in TNF-alpha and IL-6 levels, implying reduced interaction with mammalian cells in vivo. This work therefore clearly demonstrated how tailoring the nano-bio interaction could result in selective drug delivery and a reduction in toxicity.

Combinatorial Polycation Synthesis and Causal Machine Learning Reveal Divergent Polymer Design Rules for Effective pDNA and Ribonucleoprotein Delivery

The development of polymers that can replace engineered viral vectors in clinical gene therapy has proven elusive despite the vast portfolios of multifunctional polymers generated by advances in polymer synthesis. Functional delivery of payloads such as plasmids (pDNA) and ribonucleoproteins (RNP) to various cellular populations and tissue types requires design precision. Herein, we systematically screen a combinatorially designed library of 43 well-defined polymers, ultimately identifying a lead polycationic vehicle (P38) for efficient pDNA delivery. Further, we demonstrate the versatility of P38 in codelivering spCas9 RNP and pDNA payloads to mediate homology-directed repair as well as in facilitating efficient pDNA delivery in ARPE-19 cells. P38 achieves nuclear import of pDNA and eludes lysosomal processing far more effectively than a structural analogue that does not deliver pDNA as efficiently. To reveal the physicochemical drivers of P38's gene delivery performance, SHapley Additive exPlanations (SHAP) are computed for nine polyplex features, and a causal model is applied to evaluate the average treatment effect of the most important features selected by SHAP. Our machine learning interpretability and causal inference approach derives structure-function relationships underlying delivery efficiency, polyplex uptake, and cellular viability and probes the overlap in polymer design criteria between RNP and pDNA payloads. Together, combinatorial polymer synthesis, parallelized biological screening, and machine learning establish that pDNA delivery demands careful tuning of polycation protonation equilibria while RNP payloads are delivered most efficaciously by polymers that deprotonate cooperatively via hydrophobic interactions. These payload-specific design guidelines will inform further design of bespoke polymers for specific therapeutic contexts.

Small interfering RNAs (siRNAs) based gene silencing strategies for the treatment of glaucoma: Recent advancements and future perspectives

RNA-interference-based mechanisms, especially the use of small interfering RNAs (siRNAs), have been under investigation for the treatment of several ailments and have shown promising results for ocular diseases including glaucoma. The eye, being a confined compartment, serves as a good target for the delivery of siRNAs. This review focuses on siRNA-based strategies for gene silencing to treat glaucoma. We have discussed the ocular structures and barriers to gene therapy (tear film, corneal, conjunctival, vitreous, and blood ocular barriers), methods of administration for ocular gene delivery (topical instillation, periocular, intracameral, intravitreal, subretinal, and suprachoroidal routes) and various viral and non-viral vectors in siRNA-based therapy for glaucoma. The components and mechanism of siRNA-based gene silencing have been mentioned briefly followed by the basic strategies and challenges faced during siRNA therapeutics development. We have emphasized different therapeutic targets for glaucoma which have been under research by scientists and the current siRNA-based drugs used in glaucoma treatment. We also mention briefly strategies for siRNA-based treatment after glaucoma surgery.

Impact of chemistry and nanoformulation parameters on cellular uptake and airway distribution of RNA oligonucleotides

Small, synthetic oligonucleotides (ON) are of great interest as potential disease modifying drugs, mainly because of their ability to modulate previously undruggable target mutations. To date, therapeutic applications of ON are, however, limited by their physicochemical properties, including poor stability, rapid excretion and low intracellular access. In order to overcome some of these shortcomings, ON are generally formulated using nanoparticle (NP) delivery systems. Alternatively, the poor stability can be circumvented by including chemical modifications to the backbone or sugars of the ON. Some of these modifications also result in better intracellular target access of these otherwise membrane-impermeable macromolecules. Therefore, complex formulation of ON into NP in order to overcome the hurdle of intracellular access might not always be needed, especially in case of local delivery. In this study, the delivery and functionality of chemically modified ON in free form was compared to polymeric NP assisted delivery, measuring their effectivity and efficiency. For this reason, phosphorothioate (PS) backbone-modified 18-mer ON with either 2'OMe or 2'MOE-modifications were selected, capable of eliciting exon-skipping of an aberrant exon in fluorescence based in vitro and in vivo model systems. The NP consisted of poly(D,L-lactic,co-glycolic acid) and poly-β-amino-ester, previously demonstrated to successfully deliver nucleic acids via the pulmonary route. Several NP formulation parameters were tested in order to optimize the delivery of the ON, including ratio polymer:ON, NP size and concentration. The results reported here show clear differences between gymnotic and nanoparticle mediated ON delivery in terms of cellular uptake and local tissue distribution. In vitro, differences in exon-skipping efficiencies were observed with 2'OMe and 2'MOE ON either in free form or formulated in NP, with the striking observation that 2'OMe ON formulated in polymeric NP did not result in exon skipping. Gymnotic delivery of 2'MOE ON into the respiratory tract of mice resulted in functional delivery of exon-skipping ON into nasal epithelia and lungs as well as other downstream tissues and organs, pointing towards a gradual redistribution of locally delivered ONs, with limited but measurable systemic exposure. Conversely, NP-mediated delivery into the respiratory tract resulted in a more contained functional delivery at 10× lower ON doses compared to gymnotic delivery. Based on these findings we conclude that gymnotic delivery of 2'OMe or 2'MOE exon-skipping ON to the respiratory tract is effective, but that NP formulation might be advantageous in case spread of ON to non-target tissue can lead to undesired effects.

Targeted Intraceptor Nanoparticle for Neovascular Macular Degeneration: Preclinical Dose Optimization and Toxicology Assessment

Neovascular age-related macular degeneration (AMD) is treated with anti-VEGF intravitreal injections, which can cause geographic atrophy, infection, and retinal fibrosis. To minimize these toxicities, we developed a nanoparticle delivery system for recombinant Flt23k intraceptor plasmid (RGD.Flt23k.NP) to suppress VEGF intracellularly within choroidal neovascular (CNV) lesions in a laser-induced CNV mouse model through intravenous administration. In the current study, we examined the efficacy and safety of RGD.Flt23k.NP in mice. The effect of various doses was determined using fluorescein angiography and optical coherence tomography to evaluate CNV leakage and volume. Efficacy was determined by the rate of inhibition of CNV volume at 2 weeks post-treatment. RGD.Flt23k.NP had peak efficacy at a dose range of 30-60 μg pFlt23k/mouse. Using the lower dose (30 μg pFlt23k/mouse), RGD.Flt23k.NP safety was determined both in single-dose groups and in repeat-dose (three times) groups by measuring body weight, organ weight, hemoglobin levels, complement C3 levels, and histological changes in vital organs. Neither toxicity nor inflammation from RGD.Flt23k.NP was detected. No side effect was detected on visual function. Thus, systemic RGD.Flt23k.NP may be an alternative to standard intravitreal anti-VEGF therapy for the treatment of neovascular AMD.

In Vitro Cell Models for Ophthalmic Drug Development Applications

Tissue engineering is a rapidly expanding field that aims to establish feasible techniques to fabricate biologically equivalent replacements for diseased and damaged tissues/organs. Emerging from this prospect is the development of in vitro representations of organs for drug toxicity assessment. Due to the ever-increasing interest in ocular drug delivery as a route for administration as well as the rise of new ophthalmic therapeutics, there is a demand for physiologically accurate in vitro models of the eye to assess drug delivery and safety of new ocular medicines. This review summarizes current existing ocular models and highlights the important factors and limitations that need to be considered during their use.

Drug delivery to the posterior segment of the eye for pharmacologic therapy

Treatment of diseases of the posterior segment of the eye, such as age-related macular degeneration, cytomegalovirus retinitis, diabetic retinopathy, posterior uveitis and retinitis pigmentosa, requires novel drug delivery systems that can overcome the many barriers for efficacious delivery of therapeutic drug concentrations. This challenge has prompted the development of biodegradable and nonbiodegradable sustained-release systems for injection or transplantation into the vitreous as well as drug-loaded nanoparticles, microspheres and liposomes. These drug delivery systems utilize topical, systemic, subconjunctival, intravitreal, transscleral and iontophoretic routes of administration. The focus of research has been the development of methods that will increase the efficacy of spatiotemporal drug application, resulting in more successful therapy for patients with posterior segment diseases. This article summarizes recent advances in the research and development of drug delivery methods of the posterior chamber of the eye, with an emphasis on the use of implantable devices as well as micro- and nanoparticles.

Antiapoptotic properties of α-crystallin-derived peptide chaperones and characterization of their uptake transporters in human RPE cells

PURPOSE

The chaperone proteins, α-crystallins, also possess antiapoptotic properties. The purpose of the present study was to investigate whether 19 to 20-mer α-crystallin-derived mini-chaperone peptides (α-crystallin mini-chaperone) are antiapoptotic, and to identify their putative transporters in human fetal RPE (hfRPE) cells.

METHODS

Cell death and caspase-3 activation induced by oxidative stress were quantified in early passage hfRPE cells in the presence of 19 to 20-mer αA- or αB-crystallin-derived or scrambled peptides. Cellular uptake of fluorescein-labeled, α-crystallin-derived mini-peptides and recombinant full-length αB-crystallin was determined in confluent hfRPE. The entry mechanism in hfRPE cells for α-crystallin mini-peptides was investigated. The protective role of polycaprolactone (PCL) nanoparticle encapsulated αB-crystallin mini-chaperone peptides from H2O2-induced cell death was studied.

RESULTS

Primary hfRPE cells exposed to oxidative stress and either αA- or αB-crystallin mini-chaperones remained viable and showed marked inhibition of both cell death and activation of caspase-3. Uptake of full-length αB-crystallin was minimal while a time-dependent uptake of αB-crystallin-derived peptide was observed. The mini-peptides entered the hfRPE cells via the sodium-coupled oligopeptide transporters 1 and 2 (SOPT1, SOPT2). PCL nanoparticles containing αB-crystallin mini-chaperone were also taken up and protected hfRPE from H2O2-induced cell death at significantly lower concentrations than free αB-crystallin mini-chaperone peptide.

CONCLUSIONS

αA- and αB-crystallin mini-chaperones offer protection to hfRPE cells and inhibit caspase-3 activation. The oligopeptide transporters SOPT1 and SOPT2 mediate the uptake of these peptides in RPE cells. Nanodelivery of αB-crystallin-derived mini-chaperone peptide offers an alternative approach for protection of hfRPE cells from oxidant injury.

Nanomedicines for back of the eye drug delivery, gene delivery, and imaging

Treatment and management of diseases of the posterior segment of the eye such as diabetic retinopathy, retinoblastoma, retinitis pigmentosa, and choroidal neovascularization is a challenging task due to the anatomy and physiology of ocular barriers. For instance, traditional routes of drug delivery for therapeutic treatment are hindered by poor intraocular penetration and/or rapid ocular elimination. One possible approach to improve ocular therapy is to employ nanotechnology. Nanomedicines, products of nanotechnology, having at least one dimension in the nanoscale include nanoparticles, micelles, nanotubes, and dendrimers, with and without targeting ligands. Nanomedicines are making a significant impact in the fields of ocular drug delivery, gene delivery, and imaging, the focus of this review. Key applications of nanotechnology discussed in this review include a) bioadhesive nanomedicines; b) functionalized nanomedicines that enhance target recognition and/or cell entry; c) nanomedicines capable of controlled release of the payload; d) nanomedicines capable of enhancing gene transfection and duration of transfection; f) nanomedicines responsive to stimuli including light, heat, ultrasound, electrical signals, pH, and oxidative stress; g) diversely sized and colored nanoparticles for imaging, and h) nanowires for retinal prostheses. Additionally, nanofabricated delivery systems including implants, films, microparticles, and nanoparticles are described. Although the above nanomedicines may be administered by various routes including topical, intravitreal, intravenous, transscleral, suprachoroidal, and subretinal routes, each nanomedicine should be tailored for the disease, drug, and site of administration. In addition to the nature of materials used in nanomedicine design, depending on the site of nanomedicine administration, clearance and toxicity are expected to differ.

Functionalized STAT1 siRNA nanoparticles regress rheumatoid arthritis in a mouse model

AIM

To develop and characterize an RGD peptide functionalized poly(lactide-co-glycolytic) acid (PLGA) nanosystem to deliver a STAT1 siRNA to joint tissues in a mouse model of rheumatoid arthritis.

METHODS

RGD-PLGA polymer was synthesized and used in preparing functionalized nanoparticles loaded with either tracking material or siRNA. The properties of the nanoparticles and stability of siRNA after encapsulation was assessed. Nanoparticle distribution was determined both noninvasively and based on analysis of dissected organs from arthritic and healthy mice. Arthritic mice were treated with weekly doses of STAT1 siRNA-loaded nanoparticles or controls. Clinical disease was assessed. Paws of arthritic mice were sectioned for histology or processed for RNA. STAT1, Mrc-1, and IL-10 mRNA abundance was determined by quantitative PCR.

RESULTS

Nanoparticles protected the siRNA from serum degradation. The presence of RGD peptide on the nanoparticles increased paw tissue uptake in arthritic mice. Furthermore, RGD functionalization increased lung delivery of nanoparticles in arthritic mice but not in control mice. Disease regressed in the STAT1 siRNA-treated animals and progressed in all control groups. STAT1 mRNA levels were decreased in paws of treated animals, while Mrc-1 and IL-10 mRNA levels were increased.

CONCLUSION

RGD functionalized PLGA nanoparticles encapsulating STAT1-targeted siRNAs are efficacious in the treatment of established arthritis, possibly through a selective inhibition of macrophage and dendritic cell activation.

In vitro release characteristics and cellular uptake of poly(D,L-lactic-co-glycolic acid) nanoparticles for topical delivery of antisense oligodeoxynucleotides

The efficacy of antisense oligodeoxynucleotides (AsODNs) is compromised by their poor stability in biological fluids and the inefficient cellular uptake due to their size and negative charge. Since chemical modifications of these molecules have resulted in a number of non-antisense activities, incorporation into particulate delivery systems has offered a promising alternative. The aim of this study was to evaluate various poly(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles for AsODN entrapment and delivery. PLGA nanoparticles were prepared using the double emulsion solvent evaporation method. The influence of formulation parameters such as PLGA concentration and volume ratio of internal aqueous phase volume (Va1) to organic phase volume (Vo) to external aqueous phase volume (Va2) on particle size, polydispersity index (PDI) and zeta potential (ZP) was investigated using a full factorial study. The particle size increased with increasing PLGA concentrations and volume ratios, with an interaction detectable between the two factors. AsODN entrapment efficiencies ranged between 49.97% and 54.95% with no significant difference between various formulations. By fitting the in vitro release profiles to a dual first order release model it was shown that the AsODN release occurred via two processes: a diffusion controlled process in the early phase (25 to 32% within one day) and a PLGA degradation process in the latter (39 to 70% after 14 days). Cellular uptake studies using primary corneal epithelial cells suggested active transport of nanoparticles via endocytosis. PLGA nanoparticles therefore show potential to successfully entrap AsODNs, transport them into cells and release them over time due to polymer erosion.

Redefining tissue engineering for nanomedicine in ophthalmology

Working at the nanoscale means to completely rethink how to approach engineering in the body in general and in the eye in particular. In nanomedicine, tissue engineering is the ability to influence an environment either by adding, subtracting or manipulating that environment to allow it to be more conducive for its purpose. The goal is to function at the optimum state, or to return to that optimum state. Additive tissue engineering replaces cells or tissue, or tries to get something to grow that is no longer there. Arrestive tissue engineering tries to stop aberrant growth which, if left uncontrolled, would result in a decrease in function. Nano delivery of therapeutics can perform both additive and arrestive functions influencing the environment either way, depending on the targeting. By manipulating the environment at the nanoscale, the rate and distribution of healing can be controlled. It infers that potential applications of nanomedicine in ophthalmology include procedures, such as corneal endothelial cell transplantation, single retinal ganglion cell repair, check of retinal ganglion cell viability, building of nanofibre scaffolds, such as self-assembling peptides, to create a scaffold-like tissue-bridging structure to provide a framework for axonal regeneration in the case of optic nerve reconnection or eye transplantation, and ocular drug delivery. Examples of potential arrestive therapies include gene-related treatment modalities to inhibit intraocular neovascularization and to block retinal cell apoptosis. Looking towards the future, this review focuses on how nanoscale tissue engineering can be and is being used to influence that local environment.

Inhibition of ataxia-telangiectasia mutated by antisense oligonucleotide nanoparticles induces radiosensitization of head and neck squamous-cell carcinoma in mice

Ataxia-telangiectasia-mutated (ATM) is a radiosensitization gene. In the present study, we investigated the efficacy of poly(D,L-lactide-co-glycolide) (PLGA) nanoparticles containing ATM antisense oligonucleotides (ASOs) for the radiosensitization of head and neck squamous-cell carcinoma in mice, using the SCCVII cell line. Nanoparticles containing ATM ASOs were prepared with PLGA by using a double-emulsion solvent evaporation method. The results showed that the nanoparticles were suitable for intracellular uptake, and ATM ASOs inhibited ATM expression when delivered by using nanoparticles or lipofectin, but not in their free form. Meanwhile, we found that ATM reduction sensitized SCCVII cells in vitro and tumors in vivo to irradiation. In conclusion, biodegradable PLGA nanoparticles, used as a delivery carrier, enhanced intracellular uptake of ATM ASOs into SCCVII cells and the inhibitory effect of ATM ASOs. These results demonstrated that antisense ATM therapy, using PLGA nanoparticles, might provide a therapeutic benefit to patients undergoing radiation therapy for head and neck squamous-cell carcinoma.

Inhibition of the EGFR with nanoparticles encapsulating antisense oligonucleotides of the EGFR enhances radiosensitivity in SCCVII cells

The aim of this study is to evaluate the effects of antisense epidermal growth factor receptor (EGFR) nanoparticles on cell survival and radiosensitivity in the head and neck squamous cell carcinoma cell line SCCVII. Experiments were performed using the murine head-and-neck tumor cell line, SCCVII. Nanoparticle encapsulated antisense EGFR oligonucleotides were combined with radiotherapy and the relative radiosensitivity of the cells was assessed in vitro by MTT and standard colony formation. The proportion of apoptotic cells and cell cycle stages were analyzed by flow cytometry. C3H/He mice with SCCVII tumor heterografts were treated with antisense-EGFR-nanoparticles or RT alone, or with combinations of concomitant and sequential therapy. The relative radiosensitivity of the tumors was assessed in vivo by growth delay assays. The SCCVII cells were resistant to anti-EGFR nanoparticles or radiation therapy alone, but a synergic inhibition effect was observed when the therapies were combined. When the SCCVII cells were pre-treated with 2 mug of antisense-EGFR nanoparticles for 24 h and X-irradiated (4 Gy), flow cytometry analysis revealed cell cycle arrest in G(1) phase and an increased proportion of apoptotic cells. Our results show that antisense EGFR nanoparticles enhance radiosensitivity by inhibition of EGFR-mediated mechanisms of radioresistance. Collectively, these findings may have therapeutic implications because EGFR inhibition may improve the therapeutic efficacy of radiation even in the tumor cells that are resistant to anti-EGFR therapy.

Nano and microtechnologies for the delivery of oligonucleotides with gene silencing properties

Oligonucleotides (ONs) are synthetic fragments of nucleic acid designed to modulate the expression of target proteins. DNA-based ONs (antisense, antigene, aptamer or decoy) and more recently a new class of RNA-based ONs, the small interfering RNAs (siRNAs), have gained great attention for the treatment of different disease states, such as viral infections, inflammation, diabetes, and cancer. However, the development of therapeutic strategies based on ONs is hampered by their low bioavailability, poor intracellular uptake and rapid degradation in biological fluids. The use of a non-viral carrier can be a powerful tool to overcome these drawbacks. Lipid or polymer-based nanotechnologies can improve biological stability and cellular uptake of ONs, with possibility of tissue and/or cellular targeting. The use of polymeric devices can also produce a prolonged release of the ON, thus reducing the need of frequent administrations. This review summarizes advantages and issues related to the main non-viral vectors used for ON delivery.

Nanotechnologies and controlled release systems for the delivery of antisense oligonucleotides and small interfering RNA

Antisense oligonucleotides and small interfering RNA have enormous potential for the treatment of a number of diseases, including cancer. However, several impediments to their widespread use as drugs still have to be overcome: in particular their lack of stability in physiological fluids and their poor penetration into cells. Association with or encapsulation within nano- and microsized drug delivery systems could help to solve these problems. In this review, we describe the progress that has been made using delivery systems composed of natural or synthetic polymers in the form of complexes, nanoparticles or microparticles.

Multilayer composite scaffolds with mechanical properties similar to small intestinal submucosa

Use of biodegradable scaffolds to engineer new tissues has become an attractive option in various transplantation protocols. In particular, small intestinal submucosa (SIS) has generated immense interest in various tissue engineering applications because of its diverse favorable properties. However, it is a natural matrix, which leads to problems in large-scale preparations and contains sample to sample heterogeneity. In this study, we explored the formation of synthetic matrix mimicking the characteristics of the SIS. Three-dimensional composite structures were developed by sandwiching 50:50 PLGA film between porous chitosan matrices. The outer chitosan layers provide biological activity while the inner PLGA layer provides mechanical strength. PLGA films were initially perforated at 1 cm distance, and the porous chitosan matrix was formed sequentially on each side by controlled rate freezing and lyophilization technique at -80 degrees C. Scanning electron microscopy analysis showed a layered microarchitecture with chitosan filling the perforations of PLGA membrane. Urea permeability studies confirmed that the perforations were filled (negligible urea transfer across composite over 8 h). Tensile strength analysis showed that the matrices formed using 160 kDa PLGA had sufficient break stress ( approximately 4.5 MPa). Degradation analysis over 8 weeks in the presence of 10 mg/L lysozyme showed a 50% decrease in total weight and an 80% decrease in PLGA molecular weight. When cellular adhesion and actin distribution of mouse embryonic fibroblasts were evaluated, for 7 days, cells showed their typical spindle shape and redistribution of actin fibers on composite matrices. Viability studies and MMP-2/MMP-9 activity showed that the cells were viable and functional, similar to tissue culture plastic. Further, canine bladder smooth muscle cells also showed similar cell adhesion and spreading on the composite matrix. In summary, composite structures mimicking SIS were constructed and show potential as a tissue engineering material.

Intravenous transferrin, RGD peptide and dual-targeted nanoparticles enhance anti-VEGF intraceptor gene delivery to laser-induced CNV

Choroidal neovascularization (CNV) leads to loss of vision in age-related macular degeneration (AMD), the leading cause of blindness in adult population over 50 years old. In this study, we developed intravenously administered, nanoparticulate, targeted nonviral retinal gene delivery systems for the management of CNV. CNV was induced in Brown Norway rats using a 532 nm laser. We engineered transferrin, arginine-glycine-aspartic acid (RGD) peptide or dual-functionalized poly-(lactide-co-glycolide) nanoparticles to target delivery of anti-vascular endothelial growth factor (VEGF) intraceptor plasmid to CNV lesions. Anti-VEGF intraceptor is the only intracellularly acting VEGF inhibitory modality. The results of the study show that nanoparticles allow targeted delivery to the neovascular eye but not the control eye on intravenous administration. Functionalizing the nanoparticle surface with transferrin, a linear RGD peptide or both increased the retinal delivery of nanoparticles and subsequently the intraceptor gene expression in retinal vascular endothelial cells, photoreceptor outer segments and retinal pigment epithelial cells when compared to nonfunctionalized nanoparticles. Most significantly, the CNV areas were significantly smaller in rats treated with functionalized nanoparticles as compared to the ones treated with vehicle or nonfunctionalized nanoparticles. Thus, surface-functionalized nanoparticles allow targeted gene delivery to the neovascular eye on intravenous administration and inhibit the progression of laser-induced CNV in a rodent model.

Age-related macular degeneration: a target for nanotechnology derived medicines

Despite the fact that the retina is a fairly accessible portion of the central nervous system, there are virtually no treatments for early age-related macular degeneration (AMD). AMD is a degenerative retinal disease that causes progressive loss of central vision and is the leading cause of irreversible vision loss and legal blindness in individuals over the age of 50. Both environmental and genetic components play a role in its development. AMD is a multifactorial disease with characteristics that include drusen, hyperpigmentation and/or hypopigmentation of the retinal pigment epithelium (RPE), geographic atrophy and, in a subset of patients, late-stage choroidal neovascularization (CNV). Drugs that inhibit vascular endothelial growth factor (VEGF) have proven effective in treating late-stage CNV, but optimal means of drug delivery remains to be determined. Microscopic particles, whose size is on the nanometer scale, show considerable promise for drug delivery to the retina, for gene therapy, and for powering prosthetic "artificial retinas." This article summarizes the pathophysiology of AMD stressing potential applications from nanotechnology.

N-terminal acylation of the SV40 nuclear localization signal peptide enhances its oligonucleotide binding and membrane translocation efficiencies

Octanoyl and palmitoyl groups were coupled to the N-terminus of an analog of the SV40 nuclear localization signal peptide, SV126-133(Ser128), to study the effect of the fatty acid chain length on the complex formation with a single-stranded antisense oligodeoxynucleotide (ODN) and on the cellular uptake of the complex. The strongest binding affinity was observed for the palmitoylated peptide, indicating the better accessibility of the positively charged lysyl and arginyl side-chains to the phosphate groups due to the turn structures stabilized by the palmitoyl group. On increase of the peptide to ODN molar ratio (rM), gradual unstacking of the bases was observed, the maximal rate being reached at rM=10. At rM>10 restacking of the nucleotide bases was detected and the ODN was completely encapsulated in a liposome-like structure made up of palmitoylated peptides. Cell translocation experiments revealed a highly efficient cell transport of the ODN by palmitoylated SV40 peptide at rM>10.

Synthesis and characterization of PLGA nanoparticles

Poly(lactide-co-glycolide) (PLGA) nanoparticles of different physical characteristics (size, size distribution, morphology, zeta potential) can be synthesized by controlling the parameters specific to the synthesis method employed. The aim of this review is to clearly, quantitatively and comprehensively describe the top-down synthesis techniques available for PLGA nanoparticle formation, as well as the techniques commonly used for nanoparticle characterization. Many examples are discussed in detail to provide the reader with an extensive knowledge base on the important parameters specific to the synthesis method described and ways in which these parameters can be manipulated to control the nanoparticle physical characteristics.

Cell culture models of the ocular barriers

The presence of tight barriers, which regulate the environment of ocular tissues in the anterior and posterior part of the eye, is essential for normal visual function. The development of strategies to overcome these barriers for the targeted ocular delivery of drugs, e.g. to the retina, remains a major challenge. During the last years numerous cell culture models of the ocular barriers (cornea, conjunctiva, blood-retinal barrier) have been established. They are considered to be promising tools for studying the drug transport into ocular tissues, and for numerous other purposes, such as the investigation of pathological ocular conditions, and the toxicological screening of compounds as alternative to in vivo toxicity tests. The further development of these in vitro models will require more detailed investigations of the barrier properties of both the cell culture models and the in vivo ocular barriers. It is the aim of this review to describe the current status in the development of cell culture models of the ocular barriers, and to discuss the applicability of these models in pharmaceutical research.

Starch acetate microparticles for drug delivery into retinal pigment epithelium—in vitro study

Starch acetates are novel biodegradable polymers which undergo slower degradation and swelling than native starch. Retinal pigment epithelium (RPE) is an important target tissue in ocular treatment. The cellular uptake of starch acetate microparticles and degradation of starch acetate by cultured human RPE-cell line (D407) was examined. Calcein-containing starch acetate microparticles were prepared by a modified water-in-oil-in-water double-emulsion technique. The cellular uptake of the starch acetate microparticles was analysed using flow cytometry and confocal microscopy. Degradation of starch acetate films by the homogenate of lysed RPE cells was determined by gel permeation chromatography. The effect of the microparticles on RPE cell viability was determined by the MTT colorimetric assay. The mean diameter (D50%) of microparticles was 11 microm. During 3-h incubation in RPE-cell culture, 8.1 +/- 0.8% of D407 cells took up starch acetate microparticles. Confocal microscopy confirmed the internalisation of microparticles. Incubation of the starch acetate film in the RPE-cell homogenate considerably decreased the molecular weight of starch acetate in the film during 24 h. The viability of cultured RPE cells was at least 82% after 24-h incubation with the microparticles. The present results show that the starch acetate microparticles are taken up by the RPE cells and the polymer can be degraded by the enzymes in these cells. Starch acetate microparticles may be suitable for drug delivery to the RPE.