Biomaterials used in the posterior segment of the eye

Innovative Strategies for Drug Delivery to the Ocular Posterior Segment

Innovative and new drug delivery systems (DDSs) have recently been developed to vehicle treatments and drugs to the ocular posterior segment and the retina. New formulations and technological developments, such as nanotechnology, novel matrices, and non-traditional treatment strategies, open new perspectives in this field. The aim of this mini-review is to highlight promising strategies reported in the current literature based on innovative routes to overcome the anatomical and physiological barriers of the vitreoretinal structures. The paper also describes the challenges in finding appropriate and pertinent treatments that provide safety and efficacy and the problems related to patient compliance, acceptability, effectiveness, and sustained drug delivery. The clinical application of these experimental approaches can help pave the way for standardizing the use of DDSs in developing enhanced treatment strategies and personalized therapeutic options for ocular pathologies.

Vitreous Substitutes from Bench to the Operating Room in a Translational Approach: Review and Future Endeavors in Vitreoretinal Surgery

Vitreous substitutes are indispensable tools in vitreoretinal surgery. The two crucial functions of these substitutes are their ability to displace intravitreal fluid from the retinal surface and to allow the retina to adhere to the retinal pigment epithelium. Today, vitreoretinal surgeons can choose among a plethora of vitreous tamponades, and the tamponade of choice might be difficult to determine in the ever-expanding range of possibilities for a favorable outcome. The currently available vitreous substitutes have disadvantages that need to be addressed to improve the surgical outcome achievable today. Herein, the fundamental physical and chemical proprieties of all vitreous substitutes are reported, and their use and clinical applications are described alongside some surgical techniques of intra-operative manipulation. The major upcoming developments in vitreous substitutes are extensively discussed, keeping a translational perspective throughout. Conclusions on future perspectives are derived through an in-depth analysis of what is lacking today in terms of desired outcomes and biomaterials technology.

Nanomedicine and drug delivery to the retina: current status and implications for gene therapy

Blindness affects more than 60 million people worldwide. Retinal disorders, including age-related macular degeneration (AMD), diabetic retinopathy (DR), and glaucoma, are the leading causes of blindness. Finding means to optimize local and sustained delivery of drugs or genes to the eye and retina is one goal to advance the development of new therapeutics. Despite the ease of accessibility of delivering drugs via the ocular surface, the delivery of drugs to the retina is still challenging due to anatomic and physiologic barriers. Designing a suitable delivery platform to overcome these barriers should enhance drug bioavailability and provide a safe, controlled, and sustained release. Current inventions for posterior segment treatments include intravitreal implants and subretinal viral gene delivery that satisfy these criteria. Several other novel drug delivery technologies, including nanoparticles, micelles, dendrimers, microneedles, liposomes, and nanowires, are now being widely studied for posterior segment drug delivery, and extensive research on gene delivery using siRNA, mRNA, or aptamers is also on the rise. This review discusses the current state of retinal drug/gene delivery and highlights future therapeutic opportunities.

Vitreous Substitutes as Drug Release Systems

Vitreous substitutes are traditionally used to stabilize the retina after vitrectomy. In recent years, various approaches have been developed for using the vitreous substitute not only as a tamponade but also as a drug release system to tackle ocular diseases. This review provides an overview of the requirements for vitreous substitutes and discusses the current clinically applied as well as novel polymer-based vitreous substitutes as drug delivery systems, including their release mechanisms, efficiencies, challenges, and future perspectives.

Reduction in Foreign Body Response and Improved Antimicrobial Efficacy via Silicone-Oil-Infused Nitric-Oxide-Releasing Medical-Grade Cannulas

Foreign body response and infection are two universal complications that occur with indwelling medical devices. In response, researchers have developed different antimicrobial and antifouling surface strategies to minimize bacterial colonization and fibrous encapsulation. In this study, the nitric oxide (NO) donor S-nitroso-N-acetylpenicillamine (SNAP) and silicone oil were impregnated into silicone rubber cannulas (SR-SNAP-Si) using a solvent swelling method to improve the antimicrobial properties and decrease the foreign body response. The fabricated SR-SNAP-Si cannulas demonstrated a stable, prolonged NO release, exhibited minimal SNAP leaching, and maintained sliding angles < 15° for 21 days. SR-SNAP-Si cannulas displayed enhanced antimicrobial efficacy against Staphylococcus aureus in a 7-day biofilm bioreactor study, reducing the viability of adhered bacteria by 99.2 ± 0.2% compared to unmodified cannulas while remaining noncytotoxic toward human fibroblast cells. Finally, SR-SNAP-Si cannulas were evaluated for the first time in a 14- and 21-day subcutaneous mouse model, showing significantly enhanced biocompatibility compared to control cannulas by reducing the thickness of fibrous encapsulation by 60.9 ± 6.1 and a 60.8 ± 10.5% reduction in cell density around the implant site after 3 weeks. Thus, this work demonstrates that antifouling, NO-releasing surfaces can improve the lifetime and safety of indwelling medical devices.

An in situ-forming polyzwitterion hydrogel: Towards vitreous substitute application

Development of a biostable and biosafe vitreous substitute is highly desirable, but remains a grand challenge. Herein, we propose a novel strategy for constructing a readily administered vitreous substitute based on a thiol-acrylate clickable polyzwitterion macromonomer. A biocompatible multivinyl polycarboxybetaine (PCB-OAA) macromonomer is designed and synthesized, and mixed with dithiothreitol (DTT) via a Michael addition reaction to form a hydrogel in vitreous cavity. This resultant PCB-OAA hydrogel exhibits controllable gelation time, super anti-fouling ability against proteins and cells, excellent biocompatibility, and approximate key parameters to human vitreous body including equilibrium water content, density, optical properties, modulus. Remarkably, outperforming clinically used silicone oil in biocompatibility, this rapidly formed hydrogel in the vitreous cavity of rabbit eyes remains stable in vitreous cavity, showing an appealing ability to prevent significantly inflammatory response, fibrosis and complications such as raised intraocular pressure (IOP), and cataract formation. This zwitterionic polymer hydrogel holds great potential as a vitreous substitute.

Gene therapy strategies for rare monogenic disorders with nuclear or mitochondrial gene mutations

Rare monogenic disorders are a group of single-gene-mutated diseases that have a low incidence rate (less than 0.5‰) and eventually lead to patient disability and even death. Due to the relatively low number of people affected, these diseases typically fail to attract a great deal of commercial investment and research interest, and the affected patients thus have unmet medical needs. Advances in genomics biology, gene editing, and gene delivery can now offer potentially effective options for treating rare monogenic diseases. Herein, we review the application of gene therapy strategies (traditional gene therapy and gene editing) against various rare monogenic diseases with nuclear or mitochondrial gene mutations, including eye, central nervous system, pulmonary, systemic, and blood cell diseases. We summarize their pathologic features, address the barriers to gene delivery for these diseases, discuss available therapies in the clinic and in clinical trials, and sum up in-development gene delivery systems for various rare monogenic disorders. Finally, we elaborate the possible directions and outlook of gene therapy for rare monogenic disorders.

Reattachment After Foldable Capsular Vitreous Body Implantation in Severe Retinal Detachment Eyes

Purpose

To evaluate the clinical effectiveness and safety of foldable capsular vitreous body (FCVB) implantation for severe retinal detachment.

Methods

A retrospective analysis was performed on 26 patients with severe ocular trauma and one with recurrent retinal detachment. Clinical data-including surgery success, complications, retinal reattachment, vision, and intraocular pressure (IOP)-were analyzed for patients who underwent 23G pars plana vitrectomy and FCVB implantation combined with silicone oil tamponade.

Results

The mean follow-up period was 10.44 ± 2.68 months. All surgeries were smooth; the FCVBs were properly positioned and supported the retina well, and the retinal reattachment rate reached 92.59%. At the six-month follow-up, preoperative (1.30 ± 1.20) and postoperative (0.63 ± 0.79) vision was significantly different (t = 3.03, P = 0.005), and the postoperative IOP (7.93 ± 3.57 mm Hg) was lower than the preoperative IOP (13.98 ± 10.72 mm Hg) (t = 2.74, P = 0.01). Among 20 patients followed up for >12 months, preoperative (1.20 ± 0.95) and postoperative (0.75 ± 0.91) visions were significantly different (t = 1.831, P = 0.005), and the postoperative IOP (9.85 ± 6.48 mm Hg) was lower than the preoperative IOP (14.85 ± 12.17 mm Hg) (t = 1.82, P = 0.01). No endophthalmitis, sympathetic ophthalmia, and rejection of FCVB occurred during follow-up.

Conclusions

FCVB combined with silicone oil tamponade showed good efficacy and safety in severe retinal detachment treatment during the follow-up period.

Translational Relevance

Vitreous substitution is deemed a highly challenging and interesting research topic in ophthalmology. Traditional method such as silicone oil tamponade often causes various complications such as silicone oil emulsification, silicone oil migration, and corneal degeneration. The foldable capsular vitreous body as a novel vitreous substitute combined silicone oil injection into it can stay in the eyeball for a long time without obvious complications.

Substitutes and Colloidal System for Vitreous Replacement and Drug Delivery: Recent Progress and Future Prospective

Vitreoretinal surgeries for ocular diseases such as complicated retinal detachment, diabetic retinopathy, macular holes and ocular trauma has led to the development of various tamponades over the years in search for an ideal vitreous substitute. Current clinically used tamponade agents such as air, perfluorocarbons, silicone oil and expansile gases serve only as a short-term solution and harbors various disadvantages. However, an ideal long-term substitute is yet to be discovered and recent research emphasizes on the potential of polymeric hydrogels as an ideal vitreous substitute. This review highlights the recent progress in the field of vitreous substitution. Suitability and adverse effects of various tamponade agents in present day clinical use and biomaterials in the experimental phase have been outlined and discussed. In addition, we introduced the anatomy and functions of the native vitreous body and the pathological conditions which require vitreous replacement.

A self-healing and injectable hydrogel based on water-soluble chitosan and hyaluronic acid for vitreous substitute

Vitreous, an essential dioptric medium for the human eyes, must be filled with artificial materials once damaged. Carboxymethyl chitosan (CMCTS) is one of the most important water-soluble chitosan derivatives with improved biocompatibility and biodegradability. In this study, oxidized hyaluronic acid (OHA) was prepared as crosslinking reagent. CMCTS and OHA were used to develop a biocompatible, self-repairing and in-situ injectable hydrogel for vitreous substitutes. Results showed the hydrogel with controllable swelling properties, high transparency, acceptable cytocompatibility on mouse fibroblast L929 and histocompatibility in vivo. Furthermore, hydrogel was injected in-situ into the vitreous cavity after vitrectomy on New Zealand Rabbits, no significant and persistent adverse effects were observed during the 90-day follow-up period. In addition, the hydrogel maintained intraocular pressure of the operated eyes and the inherent position of the retina. Collectively, this injectable, biodegradable, nontoxic hydrogel possessed enormous potential to become a vitreous substitute material.

Vitreous substitutes: An overview of the properties, importance, and development

Vitreous or vitreous humor is a complex transparent gel that fills the space between the lens and retina of an eye and acts as a transparent medium that allows light to pass through it to reach the photoreceptor layer (retina) of the eye. The vitreous humor is removed in ocular surgery (vitrectomy) for pathologies like retinal detachment, macular hole, diabetes-related vitreous hemorrhage detachment, and ocular trauma. Since the vitreous is not actively regenerated or replenished, there is a need for a vitreous substitute to fill the vitreous cavity to provide a temporary or permanent tamponade to the retina following some vitreoretinal surgeries. An ideal vitreous substitute could probably be left inside the eye forever. The vitreous humor is transparent, biocompatible, viscoelastic and highly hydrophilic; polymeric hydrogels with these properties can be a potential candidate to be used as vitreous substitutes. To meet the tremendous demand for the vitreous substitute, many scientists all over the world have developed various kinds of vitreous substitutes or tamponade agent. Vitreous substitutes, whatsoever developed till date, are associated with several advantages and disadvantages, and there is no ideal vitreous substitute available till date. This review highlights the polymer-based vitreous substitutes developed so far, along with their advantages and limitations. The gas-based and oil-based substitutes have also been discussed but very briefly.

A New Retinal Detachment Treatment Model for Evaluation of Vitreous Tamponades

Purpose: To develop a treatment model of rhegmatogenous retinal detachment (RRD) in which the effects of various vitreous tamponades can be explored. Methods: In a primary session, detachment was produced in the right eye of 24 rabbits using vitrectomy, posterior vitreous detachment, retinal break induction, and subretinal injection of viscoelastic solution. The following day, detachments were treated in 16 eyes using SF6 (n = 8) or Healaflow® (HF, a cross-linked hyaluronic acid hydrogel, n = 8) tamponade. Animals were followed for 1 month and thereafter examined macroscopically and morphologically in hematoxylin and eosin-stained sections. Results: Retinal detachment (RD) was successfully treated using repeated surgery. Two HF eyes developed progressive vitritis and were excluded from further evaluation. Enlargement of the initial retinal rupture with concomitant RD was seen in 4/8 SF6 eyes, while all 6 HF eyes displayed an attached retina. Attached areas showed a normal retinal morphology except for in 1 HF eye with extensive degeneration. Conclusions: The RRD repeat vitrectomy model offers a possibility to explore the efficacy and complications of novel potential vitreous tamponades. Gel-based Healaflow® displays excellent anatomic reattachment, however, vitritis and retinal degeneration in some cases warrants further investigation.

Unexplained Visual Loss After Silicone Oil Removal: A 7-Year Retrospective Study

Introduction

Unexplained visual loss after removal of silicone oil from the eye has been described. The purpose of this study is to determine the incidence of unexplained loss of visual acuity after SO removal and to provide possible explanations for this phenomenon.

Methods

This retrospective study included patients that underwent vitreoretinal surgery, at Centro Hospitalar São João, between January of 2012 and October of 2018. Inclusion criterion was vitreoretinal surgery in which the chosen endotamponade was SO, followed by removal of SO and exchange with balanced salt solution (BSS) or air. After SO removal, patients with documented loss of best corrected visual acuity (BCVA) on two or more Snellen lines were analyzed and patients in which the cause of the visual loss was identified, namely OHT (intraocular pressure > 21 mmHg), retinal re-detachment, glaucoma, retinal proliferative membrane formation, or corneal decompensation, were excluded. All patients with unexplained visual loss underwent spectral domain optical coherence tomography (SD-OCT) to exclude causes of visual reduction such as cystoid macular edema, epiretinal membrane, or ellipsoid/interdigitation zone disruption. A p value less than 0.05 was considered statistically significant.

Results

A total of 46 eyes underwent SO tamponade and SO removal during the study period. In 34.8% of the cases (n = 16) there was visual acuity loss in at least two Snellen lines. Of 46 eyes, 23.9% (n = 11) showed vision loss due to known secondary causes. Unexplained loss of visual acuity after SO removal occurred in 10.9% of cases. OHT during silicone endotamponade (p = 0.046) and silicone emulsification (p = 0.001) were identified as factors associated with unexplained visual loss after SO removal.

Conclusion

Unexplained loss of visual acuity after SO removal occurred in 10.9% of cases. OHT during silicone endotamponade and SO emulsification were identified as important factors in the ethology of this phenomenon.

Safety of silicone oils as intraocular medical device: An in vitro cytotoxicity study

This study aimed to assess the cytotoxic effect of low molecular weight components (LMWC) and conventional silicone oils (SOs) 1000 cSt with different degree of purification (raw, intermediate, and purified) using in vitro cytotoxicity tests. Direct contact cytotoxicity tests were performed in BALB 3T3 and human retinal pigment epithelial cells (ARPE-19) using quantitative and qualitative evaluation according to the ISO 10993-5 (2009) standards. Conventional SOs 1000 cSt in form of raw, intermediate (intermediate product obtained during distillation process), and purified SO (final product after distillation) and a concentrate of LMWC (including siloxane chains with molecular weight up to 1557 g/mol) were directly applied to 100% of cell layer area for 24 h. Cell viability was quantified using 3-(4,5-dimethylthiazole-2-yl)-2,5-28 diphenyltetrazolium bromide (MTT) and neutral red uptake assays in ARPE-19 and BALB3T3, respectively. All tested samples, including the concentrate of LMWC, resulted to be not cytotoxic according to ISO 10993-5 in both qualitative and quantitative evaluations. However, the cellular viability was significantly higher in the intermediate and purified SO compared with the raw SO in ARPE-19 cells. No reduction in cell viability was detected by LMWC. The absence of cytotoxicity was observed for all tested samples in both BALB3T3 and ARPE-19 after 24 h of application. A direct cytotoxic effect is not likely to be involved in the potential complications related to SO and LMWC. Long-term potential adverse effects of SO could be related to the raw material and to different concentrations of LMWC.

Comparative Study of Chemical Composition, Molecular and Rheological Properties of Silicone Oil Medical Devices

Purpose

We evaluated chemical composition, and molecular and rheological properties in 10 commercially available silicone oils (SilOils), focusing on siloxane chains of low molecular weight (LMW components, LMWC) that are known to be “impurities” produced during the SilOil synthesis process.

Methods

We assessed the type of SilOil polymer and molecular weight distribution (MWD) by spectroscopy and conventional size exclusion chromatography, respectively. From the Cumulative MWD, we calculated the fractions of LMWC with molecular weight (M): ≤2000, ≤5000, and ≤10,000 g/mol. Due to the low MW, the content of LMWC with M ≤1000 g/mol was determined by gas chromatography-mass spectrometry. The dynamic viscosity (η) was assessed by rotational rheometry.

Results

For all SilOils, the polymer was polydimethylsiloxane. The samples differed significantly in terms of MWD and relative LMWC fractions. Specifically, the relative fraction of all LMWC (M ≤10,000 g/mol) ranged from 2.31% to 9.40% and the content of LMWC with M ≤1000 g/mol also varied significantly (range, 51–1151 ppm). The η values were different between the SilOils, and, for many of them, from the declared viscosity.

Conclusions

Commercially available SilOils differ significantly in molecular and rheologic features. These compounds contain a significant amount of LMWC, “impurities” generated during the synthesis process, acting as emulsifier, potentially inducing ocular inflammation and toxicity.

Translational Relevance

The amount of impurities in different SilOils may influence significantly their biocompatibility.

Development of microemulsions for ocular delivery

Microemulsions (MEs) are thermodynamic stable dispersion of oily phase and aqueous phase stabilized by surfactants and co-surfactants, and are a small droplet size of less than 100 nm. MEs are appropriate systems for ocular drug delivery because they improve ocular drug retention, extended duration of action, high ocular absorption, permeation of loaded drugs and effortlessness of preparation and administration. This review is an effort to summarize the recent development in the area of MEs, self-emulsifying drug delivery systems, which are examined in relation to their uses in ocular drug delivery. The noteworthy patent, toxicity and stability issues related to these ME systems are also explored here.

Non-viral strategies for ocular gene delivery

The success of gene therapy relies on efficient gene transfer and stable transgene expression. The in vivo efficiency is determined by the delivery vector, route of administration, therapeutic gene, and target cells. While some requirements are common to several strategies, others depend on the target disease and transgene product. Consequently, it is unlikely that a single system is suitable for all applications. This review examines current gene therapy strategies, focusing on non-viral approaches and the use of natural polymers with the eye, and particularly the retina, as their gene delivery target.

Facile Noninvasive Retinal Gene Delivery Enabled by Penetratin

Gene delivery to the posterior segment of the eye is severely hindered by the impermeability of defensive barriers; therefore, in clinical settings, genomic medicines are mainly administered by intravitreal injection. We previously found that penetratin could transport the covalently conjugated fluorophore to the fundus oculi by topical instillation. In this study, gene delivery systems enabled by penetratin were designed based on electrostatic binding to target the retina via a noninvasive administration route and prepared with red fluorescent protein plasmid (pRFP) and/or poly(amidoamine) dendrimer of low molecular weight (G3 PAMAM). Formulation optimization, structure confirmation, and characterization were subsequently conducted. Penetratin alone showed limited ability to condense the plasmid but had powerful uptake and transfection by corneal and conjunctival cells. G3 PAMAM was nontoxic to the ocular cells, and when introduced into the penetratin-incorporated complex, the plasmid was condensed more compactly. Therefore, further improved cellular uptake and transfection were observed. After being instilled in the conjunctival sac of rats, the intact complexes penetrated rapidly from the ocular surface into the fundus and resided in the retina for more than 8 h, which resulted in efficient expression of RFP in the posterior segment. Intraocular distribution of the complexes suggested that the plasmids were absorbed into the eyes through a noncorneal pathway during which penetratin played a crucial role. This study provides a facile and friendly approach for intraocular gene delivery and is an important step toward the development of noninvasive gene therapy for posterior segment diseases.

Internal Osmotic Pressure as a Mechanism of Retinal Attachment in a Vitreous Substitute

In this study, the possibility of using the internal osmotic pressure of intraocular polymeric hydrogel materials to attach the retina in the repair of a retinal tear or hole was investigated. This is in contrast to the conventional methods of retinal detachment repair (intraocular gas, polydimethylsiloxane, or n-perfluorooctane), which rely on surface tension and have recognized limits. The system selected for implementation of this scheme was based on an acrylamide copolymer that was crosslinked in an aqueous solution to provide a transparent hydrogel which allowed control of the swelling pressure. Synthetic hydrogels, such as those selected here, provide an alternative to materials currently used as vitreous prostheses.

Stimuli responsive drug delivery application of polymer and silica in biomedicine

In the last decade, using polymer and mesoporous silica materials as efficient drug delivery carriers has attracted great attention.

Influence of self-assembling peptide nanofibre scaffolds on retinal differentiation potential of stem/progenitor cells derived from ciliary pigment epithelial cells

Aim of the study was to investigate the influence of the self-assembling peptide nanofibre scaffolds (SAPNs) on the growth, proliferation and retinal neuronal differentiation of the stem/progenitor cells (SCs) derived from the ciliary pigment epithelium (CPE) of human cadaveric eye. Here SAPNs (RADA16-I, PM), which is well described in previous studies, commercially available and xeno-free. The CPE cells isolated were cultured in DMEM/F12 supplemented with N2 and growth factors such as basic fibroblast growth factor and epidermal growth factor, encapsulated in the scaffolds. The entrapped SCs actively expanded and formed clone-like clusters in the scaffolds. Many cells in the cluster were proliferating, as revealed by 5-bromo-2-deoxyuridine uptake and could be maintained for up to 6 days and expressed neural progenitor markers such as β-III tubulin, Nestin, Pax6 and Musashi1. Upon differentiation of these cells in conditioned medium, the cells exhibited retinal neuronal markers such as s-Opsin, rhodopsin and Recoverin. The RT² profiler polymerase chain reaction array experiments showed selective gene expression, possibly involved in neural stem/progenitor cell adhesion and differentiation. These findings suggest the suitability of the three-dimensional culture system for the proliferation and maintenance of CPE stem/progenitor cells (CPE-NS) and for possible use in ex vivo studies of small molecules, drug deliveries for retinal diseases and for use in combination with directed stem/progenitor cell differentiation. and ultimately for tissue replacement therapies. Copyright © 2014 John Wiley & Sons, Ltd.

Poly(ethylene glycol) hydrogels with adaptable mechanical and degradation properties for use in biomedical applications

Requirements of hydrogels for drug delivery, wound dressings, and surgical implantation can be extensive, including suitable mechanical properties and tailorable degradation time frames. Herein, an adaptable PEG-based hydrogel, whose mechanical properties and degradation rate can be systematically adjusted to meet these criteria by altering simple variables such as the PEG molecular weight, is described. The performance of these hydrogels in three physical manipulations (pushing, pulling, and folding), representative of manipulations that they may undergo during typical biomedical use, is also assessed. While not all of these formulations can withstand these manipulations, a subset did, and it is intended to further optimize these formulations for specific clinical applications. Additionally, the outcomes of the physical manipulation tests indicate that simply having a high modulus does not correlate with biomedical applicability.

Evaluation of RGD peptide hydrogel in the posterior segment of the rabbit eye

The aim of this study was to evaluate the biocompatibility and biodegradability of RGD peptide hydrogel in the posterior segment of the eye as a biomaterial potentially useful for sustained drug delivery systems. RGD peptide hydrogel was injected into the vitreous cavity and suprachoroidal space of rabbit eyes. Clinical follow-up and histological observation were performed up to four weeks. The biodegradability was also evaluated by the lifetime of the hydrogel which was defined by ophthalmoscopic observation or ultrasonography. The results showed that RGD peptide hydrogel was well tolerated in the vitreous cavity and suprachoroidal space, and disappeared from the injection sites progressively. As for suprachoroidal injection, the hydrogel was clearly identified by ultrasound echography and was confirmed innoxious to the retinal vessels by fluorescein angiography. Histological observations showed that the structures of retina, choroid and other tissues around the injection site remained normal after the injection. The lifetime of the hydrogel was 25.7 ± 2.65 days and 14.3 ± 3.3 days in the vitreous cavity and suprachoroidal space, respectively. The results obtained demonstrated that RGD peptide hydrogel, which showed excellent biocompatibility and favorable biodegradability in the posterior segment of rabbit eyes, appears to be a promising biomaterial to deliver drugs focally to the choroid and the retina.

Comprehensive analysis of inflammatory immune mediators of the intraocular fluid aspirated from the foldable capsular vitreous body filled-eyes

PURPOSE

To analyze the level of human inflammatory immune mediators in the intraocular fluid aspirated from foldable capsular vitreous body (FCVB) filled-eyes during FCVB removal surgery, 3 months after implantation.

METHODS

8 samples of intra-FCVB fluids (n = 8) were collected from 8 FCVB filled patients in our previous FCVB exploratory clinical trial. The intra-FCVB fluids were aspirated from the FCVB filled-eyes during the FCVB removal surgeries at the third month. For the control groups, the vitreous fluids were collected from patients with idiopathic macular hole (n = 9) or rhegmatogenous retinal detachment (n = 6) during pars plana vitrectomy. A multiplex immunoassay was used to determine levels of 9 cytokines (IL-1β, IL-2, IL-6, IL-8, IL-10, IL-17, TNF-α, IFN-γ and VEGF) in these samples. The VEGF level of some intra-FCVB fluids (n = 6) were re-tested using enzyme-linked immunosorbent assay (ELISA).

RESULTS

In the intra-FCVB fluids, 9 cytokines concentrations of most samples (n = 5) measured by Multiplex immunoassay showed low values, except for Patient 02, 06, and 09. The VEGF concentrations of some intra-FCVB fluids (n = 6) tested by ELISA were in accordance with Multiplex immunoassay results. For all eight patients (n = 8), the concentrations of IL-1β, IL-2, IL-6, TNF-α, IFN-γ and VEGF were slightly higher as compared to the idiopathic macular hole control group. While, the concentrations of IL-8, IL-10, and IL-17 were not statistically significant different compared with the idiopathic macular hole control samples. Most cytokines concentrations (IL-2, IL-6, IL-8, IL-10, IL-17, TNF-α, IFN-γ, VEGF) were not statistically significant different compared to the rhegmatogenous retinal detachment control group except IL-1β.

CONCLUSIONS

The FCVB had sufficient porosity to allow cytokines to pass through. This study first discovered that the FCVB possesses favorable permeability of proteins in the human eye.

Porous polysulfone coatings for enhanced drug delivery

The synthesis of a porous polysulfone (PSU) coating for use in drug delivery applications is presented. PSU can serve as a functional surface coating for drug delivery vehicles, such as intraocular biomicrorobots. The coatings can be applied using spin coating or dip coating. The porosity is introduced by selectively dissolving calcium carbonate nanoparticles embedded in the bulk polymer. The network of pores thus formed increases by a factor of thirty the amount of Rhodamine B (model drug) that can be loaded and by a factor of fifteen the amount that can be released. The films do not affect cell viability and exhibit poor cell adhesion. The straightforward synthesis and predictability of porosity enables the tuning of the amount of drug that can be loaded.

Carbon dioxide laser-induced combustion of extravasated intraocular silicone oil in the eyelid mimicking xanthelasma

A 48-year-old woman with a history of retinal detachment repair with vitrectomy, scleral buckling, and silicone oil with subsequent oil removal was referred for unilateral upper eyelid ptosis with edema and overlying skin changes simulating xanthelasma. During surgical excision, a white flare-like plume was noted when the carbon dioxide (CO2) laser was used to make the incisions. The pathology report confirmed silicone oil intrusion in the conjunctiva and upper eyelid. A postoperative in vitro experiment showed that silicone oil was readily ignited by the CO2 laser.

Evaluation of the levofloxacin release characters from a rabbit foldable capsular vitreous body

The authors have manufactured a novel rabbit foldable capsular vitreous body (FCVB). The aim of this study was to determine whether this rabbit FCVB can release levofloxacin in vitro and in vivo, and to evaluate the release characteristics. In vitro, the rabbit FCVB with levofloxacin 500 μg/mL was immersed in cups of modified Franz diffusion cells. Following this, 200 μL of liquid was aspirated at intervals from 10 minutes to 24 hours. In vivo, the FCVB with levofloxacin was implanted into the right eyes of five rabbits. After implantation, the aqueous humor was aspirated on days 1, 7, 14, 28, and 56. The levofloxacin concentrations in the cups and aqueous humor samples were detected by high-performance liquid chromatography–tandem mass spectrometry. The FCVB was observed under a scanning electron microscope. The results showed that the released levofloxacin was stabilized at 20 ng/mL at time points from 10 minutes to 24 hours in vitro. In vivo, levofloxacin concentrations in the aqueous humor were 132, 50, 39, 11, and 15 ng/mL on days 1, 7, 14, 28, and 56, respectively. In the FCVB capsules, 300 nm apertures were observed. These results suggest the rabbit FCVB released levofloxacin stably in vitro and sustainably in vivo. This study provides a novel combined approach, with the FCVB as a vitreous substitute and drug delivery system for the treatment of bacterial endophthalmitis.