Prefilled syringes for intravitreal drug delivery

[Translated article] Syringes for intraocular administration: A systematic review

OBJECTIVE

The off-label use in clinical practice of non-approved syringes for intravitreal drug administration has resulted in the detection of silicone oil drops in the vitreous of some patients. This situation derives from the lack of approved syringes for intraocular use in the Spanish market. The aim of this work is to review the use of syringes for intraocular administration, as well as to search for alternatives that meet the legal requirements for these unmet needs.

METHOD

A systematic review was performed following the PRISMA 2020 guidelines by searching PubMed with the descriptors: (silicone) AND (syringes) AND ((intraocular) OR (intravitreal)) and filtering all existing publications from January 2006 to December 2023, including all those articles dealing with silicone oil release in intravitreal injections and analysing the possible consequences.

RESULTS

Sixty-eight results were found, 23 of which were excluded because they did not deal with the subject under study, leaving a total of 45 articles for the systematic review. These were classified according to the conclusions obtained in 4 groups: the adverse reactions produced by silicone; the administration technique; the physicochemical aspects of silicone release; and the characteristics of the medical device. After reviewing the current manufacturers and technical data sheets of commercialised syringes, the existing syringes for this use have been collected, finding 2 that will probably be commercialised in Spain at the beginning of 2024: Zero Residual™ 0.2 ml SiO-free and VitreJect® Ophthalmic.

CONCLUSIONS

From the results obtained, it can be interpreted that the use of syringes and needles with silicone for intravitreal use is a concern for health professionals due to the implications and consequences that may arise in patients, the most important being adverse reactions, so it is necessary to have silicone-free syringes on the market that are specific for intraocular use. Safety and legality in the use of intraocular syringes and needles is essential to guarantee ocular integrity and patient health.

Syringes for intraocular administration: Systematic review

OBJECTIVE

The off-label use in clinical practice of non-approved syringes for intravitreal drug administration has resulted in the detection of silicone oil drops in the vitreous of some patients. This situation derives from the lack of approved syringes for intraocular use in the Spanish market. The aim of this work is to review the use of syringes for intraocular administration, as well as to search for alternatives that meet the legal requirements for these unmet needs.

METHOD

A systematic review was performed following the PRISMA 2020 Guidelines by searching PubMed with the descriptors: "silicone" AND "syringes" AND ("intraocular" OR "intravitreal") and filtering all existing publications from January 2006 to December 2023, including all those articles dealing with silicone oil release in intravitreal injections and analysing the possible consequences.

RESULTS

Sixty-eight results were found, 23 of which were excluded because they did not deal with the subject under study, leaving a total of 45 articles for the systematic review. These were classified according to the conclusions obtained in 4 groups: the adverse reactions produced by silicone, the administration technique, the physicochemical aspects of silicone release, and the characteristics of the medical device. After reviewing the current manufacturers and technical data sheets of commercialized syringes, the existing syringes for this use have been collected, finding two that will probably be commercialized in Spain at the beginning of 2024: Zero Residual™ 0.2 ml SiO-free and VitreJect® Ophthalmic.

CONCLUSIONS

From the results obtained, it can be interpreted that the use of syringes and needles with silicone for intravitreal use is a concern for health professionals due to the implications and consequences that may arise in patients, the most important being adverse reactions, so it is necessary to have silicone-free syringes on the market that are specific for intraocular use. Safety and legality in the use of intraocular syringes and needles is essential to guarantee ocular integrity and patient health.

Glycosylation differences of an anti-VEGF monoclonal antibody (PRO-169) and its extensive comparison with Bevacizumab

PRO-169 is an anti-VEGF monoclonal antibody developed by Laboratorios Sophia that shares its sequence with Bevacizumab (BVZ); though, PRO-169 is intended for intravitreal administration. In this study, analytical characterization showed that PRO-169 had glycosylation differences in comparison to BVZ reference product (RP); since it had more content of G1F, G2F, sialic acid and high mannose. Further investigation was performed to evaluate if differences between both products would affect the efficacy and safety profile of PRO-169. PRO-169 had no alteration in its in vitro biological activity; moreover, no cytotoxicity or immunogenicity concerns should be expected as demonstrated by different orthogonal methods at analytical, in vitro and in vivo assays. These results support moving to the clinical testing of PRO-169 since no major complications will be expected with its clinical use for the treatment of ophthalmic diseases.

Reduced Incidence of Intravitreal Injection-Related Endophthalmitis With Prefilled Syringes

Purpose: To evaluate the incidence and clinical characteristics of intravitreal injection-related endophthalmitis cases with antivascular endothelial growth factor (anti-VEGF) medications manufactured as prefilled syringes or non-prefilled preparations. Methods: This retrospective chart review comprised eyes that received intravitreal anti-VEGF at a single-specialty retina practice from January 1, 2014, to December 31, 2019. Eyes diagnosed with injection-related endophthalmitis were identified. Demographic and clinical data were abstracted from medical records, including the type of anti-VEGF agent, baseline and follow-up corrected visual acuity (VA), and microbiologic findings. Results: The review identified 88 cases of intravitreal anti-VEGF injection-related endophthalmitis and 325 990 total injections. Total injections included 32 045 (9.8%) bevacizumab (BEV), 93 073 (28.6%) ranibizumab (RAN), 122 947 (37.7%) aflibercept (AFL), and 77 925 (23.9%) ranibizumab prefilled syringe (RANPFS). Ten of the endophthalmitis cases were related to BEV, 21 to RAN, 45 to AFL, and 12 to RANPFS. The endophthalmitis rate was lowest for RANPFS (0.0154%) (BEV, 0.0312%; RAN, 0.0226%; AFL, 0.0366%) (P = .030). Thirty-four (41.5%) of 82 samples were culture positive. RANPFS had a significantly lower rate of culture-proven postinjection endophthalmitis than the other agents (P = .003). The mean VA for endophthalmitis cases related to RANPFS vs non-prefilled agents was similar at presentation (Snellen 20/2092 vs 20/2327) and at the 3-month follow-up (Snellen 20/201 vs 20/272) (both P > .05). Conclusions: Anti-VEGF medications in prefilled syringes may reduce the risk for medication contamination during injection preparation. RANPFS was associated with a lower rate of injection-related endophthalmitis than non-prefilled anti-VEGF medications.

Reported Rates of Intraocular Inflammation with Intravitreal Aflibercept Administered via Pre-Filled Syringe or from Vials in Clinical Practice Between 2012 and 2022

Purpose

To determine the reported rates of intraocular inflammation (IOI) in patients treated with intravitreal aflibercept (IVT-AFL) 2 mg in routine clinical practice (ie, outside interventional studies), across all indications and within all countries (excluding the United States), with access to either the vial presentation or pre-filled syringe (PFS).

Patients and methods

A search was conducted using the Bayer EYLEA^® Global Safety Pharmacovigilance Database for reported cases of IOI and IVT-AFL use between October 2012 and March 31, 2022.

Results

With more than 10 years of post-marketing experience with the IVT-AFL vial presentation (>25 million sold units), and over 2 years of experience with the PFS of IVT-AFL (>6.7 million sold units) the rate of any IOI, including endophthalmitis, outside the United States was 0.3 events per 10,000 units for the PFS and 1.2 events per 10,000 units for the vial presentation. The event rates specifically for endophthalmitis were 0.1 per 10,000 units for the IVT-AFL PFS and 0.6 per 10,000 units for the IVT-AFL vial presentation.

Conclusion

In patients with retinal diseases treated in routine clinical practice with IVT-AFL either from a vial or the PFS, medically important adverse events of IOI, and in particular, endophthalmitis, are infrequently reported events. Numerically, reported rates of IOI and endophthalmitis are low for the vial presentation and even lower for the PFS.

Ocular Injection Techniques for Retinitis Pigmentosa: Intravitreal, Subretinal, and Suprachoroidal

Ocular gene therapy represents an emerging and promising therapeutic approach for the treatment of several of the inherited retinal diseases. Currently, the focus has been to investigate monogenic inherited retinal disorders. Genetic and cellular therapies can be delivered to the eye by various injection techniques, including those that are intravitreal, subretinal, and suprachoroidal. Each of these three delivery methods are discussed with regard to their historical background, indications, surgical steps, and follow-up.

Preventive factors, diagnosis, and management of injection-related endophthalmitis: a literature review

BACKGROUND

Intravitreal medication injections represent the gold standard treatment for a variety of potentially blinding chorioretinal vascular diseases. Despite their excellent safety profile, they are associated with the feared complication of injection-related endophthalmitis (IRE). Though the overall incidence of IRE is low, due to the ever-increasing number of injections being performed, it is a complication that all retina specialists are likely to encounter. This article reviews various factors that could potentially influence the risk of IRE and discusses evidence-based strategies for management.

METHOD

PubMed was searched for keywords "intravitreal injection" and "endophthalmitis" from the period of 1995-2021. Relevant articles were reviewed and selected articles were analyzed with respect to the incidence, potential preventive factors, clinical presentation, microbial profile, management, and outcomes for IRE.

RESULTS

There is strong consensus supporting the use of povidone iodine topical antiseptic, eyelid retraction away from the injection site, and avoiding treatment of eyes with active surface or eyelid disease, but there is less agreement on the use of face masks versus "no-talking" policies and optimal anesthetic technique. Current evidence comparing tap and inject or early vitrectomy for treatment of IRE is inadequate to determine an optimal treatment strategy.

CONCLUSION

Intravitreal injections are sight saving, but even using established prophylactic measures there remains a small but real risk of infectious injection-related complications. Further investigations comparing tap and inject versus vitrectomy may help to establish optimal treatment, although the rarity of IRE makes designing adequately powered prospective trials a difficult task.

Transient Vision Loss Associated with Prefilled Aflibercept Syringes

Purpose

To describe cases of significant vision loss after intravitreal aflibercept administration using prefilled syringes (PFS) and to study the relationships among syringe design, injection speed, and injection force.

Design

Retrospective case series and experimental study.

Participants

Twelve patients who received intravitreal aflibercept via PFS.

Methods

All retina specialists (n = 13) at Oregon Health & Science University and the Veterans Affairs Portland Medical Center were queried in December 2020 to report episodes of significant vision loss after aflibercept PFS use. Chart review was completed for all affected patients. Using a commercially available force measuring system, injection force was measured for aflibercept PFS, ranibizumab PFS, and a tuberculin syringe at various injection speeds.

Main Outcome Measures

Number of significant vision loss episodes after aflibercept PFS use and average injection force (Newtons) at various injection speeds across different syringes.

Results

Ten specialists (76.9%) reported a perceived increase in vision loss after injection with aflibercept PFS. Sixteen events of light perception or worse vision were reported immediate after aflibercept PFS use. Chart review was available for 12 of these events. The indication for aflibercept was exudative age-related macular degeneration (n = 8), diabetic macular edema (n = 3), and central serous chorioretinopathy (n = 1). The median age of affected patients was 71 years (range, 49–94 years). Two patients were being treated for glaucoma (n = 1) or ocular hypertension (n = 1); 1 patient was a glaucoma suspect. Anterior chamber paracentesis was performed in 4 patients to normalize intraocular pressure (IOP) promptly. Laboratory experiments demonstrated that higher injection speeds were associated with higher injection forces for all syringe types. Injection forces were consistently greater with aflibercept PFS than with the ranibizumab PFS or tuberculin syringe (P < 0.0001).

Conclusions

Retina specialists at our institutions have noted numerous cases of severe transient vision loss with aflibercept PFS use. The average injection force may be greater with the aflibercept PFS when compared with other intravitreal anti–vascular endothelial growth factor (VEGF) options. Additional clinical studies are needed to understand better how syringe design and fluid dynamics may contribute to vision loss after injection.

Impact of the COVID-19 pandemic on patients receiving intravitreal injections

We analyzed the economic benefits versus safety risks of sharing anti-vascular endothelial growth factor (VEGF) vials during the coronavirus disease (COVID-19) pandemic. This single-center retrospective study analyzed the data of patients with neovascular age-related macular degeneration (nAMD), proliferative diabetic retinopathy (PDR) and retinal vein occlusion (RVO) who received anti- VEGF between January 2016 and July 2021 at Renmin Hospital, Wuhan University, China. Costs were compared of the two protocols of intravitreal injections (IVIs) of ranibizumab, aflibercept and conbercept after (i) splitting the vial content for use in two patients and after (ii) disposal of the remaining vial content after use in a single patient, with the COVID-19 outbreak considered as the demarcation point. The incidence rates of post-injection endophthalmitis (PIE) pre- and post-outbreak were analyzed. The mean cost of a single IVI increased by 33.3%, from 3917.67?71.69 to 5222.67?84.98 Chinese Yuan during the pandemic. The incidences of IVI-related culture-positive PIE were 0.0134% (3 in 22448) and 0.0223% (1 in 4479), respectively, before and after the pandemic (P=0.6532). We conclude that vial sharing of IVIs in a large clinical institution is not associated with increased PIE risk and can significantly reduce the cost of therapy.

THE RELATIONSHIP BETWEEN STOPPER POSITION AND INJECTION VOLUME IN RANIBIZUMAB AND AFLIBERCEPT PREFILLED SYRINGES

PURPOSE

To determine the relationship between stopper position and injection volume in aflibercept and ranibizumab prefilled syringes (PFS).

METHODS

Empty aflibercept 2.0 mg PFS and ranibizumab 0.3 mg and 0.5 mg PFS were collected and refilled with saline. The stopper was positioned relative to the preprinted mark, and resulting injection volumes were recorded. The position for double the on-label volume was confirmed with repeated testing. The quantitative relationship between position and volume was calculated.

RESULTS

In ranibizumab PFS, doubling the distance increased the volume injected by 2.6 times. Positioning the stopper 4.0, 3.0, 2.0, and 0 mm proximal to and 1.0 mm distal to the mark injected volumes of 0.13, 0.1, 0.08, 0.05, and 0.03 mL, respectively. The relationship between position (x) and volume (y) was y = 0.019x + 0.048. In aflibercept PFS, doubling the distance increased the volume injected by 3.2 times. Positioning the stopper 2.5, 2.0, 1.0, and 0 mm proximal to and 1.0 mm distal to the mark injected volumes of 0.16, 0.14, 0.11, 0.05, and 0.02 mL, respectively. The relationship between position (x) and volume (y) was y = 0.041x + 0.059.

CONCLUSION

Proper positioning of the stopper at the preprinted mark accurately delivers the on-label volume with both the ranibizumab and aflibercept PFS. However, small variations in stopper position appear to have substantial effects on the volume of drug injected.

Silicone microbubbles after anti-vascular endothelial growth factor injections in patients with wet age-related macular degeneration: incidence, quantification and secondary optical coherence tomography artfacts

PURPOSE

To report the incidence and quantity of silicone oil microbubbles and the relationship with the number of intravitreal anti-vascular endothelial growth factor (VEGF) injections and evaluate if microbubbles induce artefacts on optical coherence tomography (OCT) images.

METHODS

Observational, descriptive, cross-sectional study. Patients with wet age-related macular degeneration were included who had been treated for 1 year minimally with anti-VEGF injections repackaged in the hospital pharmacy. Detection and quantification of silicone microbubbles by mydriatic biomicroscopic examination were conducted 1 month after the last injection. The numbers of microbubbles were quantified on a scale of 0-3: 0, none; 1 scarce (1-10 microbubbles); 2 moderate (10-30); or 3 numerous (>30). Shadowing on OCT images was classified as 0-3: 0, none; 1 obscuring some retinal layers; 2 obscuring all retinal layers; or 3 obscuring the retinal thickness.

RESULTS

The study included 142 eyes of 98 patients (mean age, 82.4 years + 7.3; range, 65-97) treated with 2377 injections. Microbubbles were detected in 127 (89.4%) eyes, 62 (43.6%) with numerous microbubbles and 36 (25.4%) and 29 (20.4%), respectively, with scarce and moderate numbers. A positive correlation was found between the numbers of injections and intravitreal silicone (rho, 0.7). Optical coherence tomography (OCT) artefacts were detected in 11 eyes; the artefacts obscured all retinal layers in three eyes. No significant relationship could be established between the appearance of floaters and the microbubbles.

CONCLUSION

The presence and number of silicone microbubbles were correlated with the number of intravitreal injections. Microbubbles can produce OCT artefacts, which can hinder the treatment decision.

Chemical-gas Sterilization of External Surface of Polymer-based Prefilled Syringes and Its Effect on Stability of Model Therapeutic Protein

To reduce the risk of infection during intravitreal injections, the external surface of prefilled syringes (PFSs) must be sterilized. Usually, ethylene oxide (EO) gas or vaporized hydrogen peroxide (VHP) is used for sterilization. More recently, nitrogen dioxide (NO₂) gas sterilization has been developed. It is known that gas permeability is approximately zero into glass-PFSs. However, polymer-PFSs (P-PFSs) have relatively high gas permeability. Therefore, there are concerns about the potential impact of external surface sterilization on drug solutions in P-PFSs. In this study, P-PFSs [filled with water for injection (WFI) or human serum albumin (HSA) solution] were externally sterilized using EO, VHP, and NO₂ gases. For the WFI-filled syringes, the concentration of each gas that ingressed into the WFI was measured. For the HSA solution-filled syringes, the physical and chemical degradation of HSA molecules by each sterilant gas was quantified. For the EO- or VHP-sterilized syringes, the ingressed EO or hydrogen peroxide (H₂O₂) molecules were detected in the filled WFI. Additionally, EO-adducted or oxidized HSA molecules were observed in the HSA-filled syringes. In contrast, the NO₂-sterilized WFI-filled syringes exhibited essentially immeasurable ingressed NO₂, and protein degradation was not detected in HSA-filled syringes.

Amine oxidase copper-containing 3 (AOC3) inhibition: a potential novel target for the management of diabetic retinopathy

Background

Diabetic retinopathy (DR), a microvascular complication of diabetes, is the leading cause of visual impairment in people aged 20–65 years and can go undetected until vision is irreversibly lost. There is a need for treatments for non-proliferative diabetic retinopathy (NPDR) which, in comparison with current intravitreal (IVT) injections, offer an improved risk–benefit ratio and are suitable for the treatment of early stages of disease, during which there is no major visual impairment. Efficacious systemic therapy for NPDR, including oral treatment, would be an important and convenient therapeutic approach for patients and physicians and would reduce treatment burden. In this article, we review the rationale for the investigation of amine oxidase copper-containing 3 (AOC3), also known as semicarbazide-sensitive amine oxidase and vascular adhesion protein 1 (VAP1), as a novel target for the early treatment of moderate to severe NPDR. AOC3 is a membrane-bound adhesion protein that facilitates the binding of leukocytes to the retinal endothelium. Adherent leukocytes reduce blood flow and in turn rupture blood vessels, leading to ischemia and edema. AOC3 inhibition reduces leukocyte recruitment and is predicted to decrease the production of reactive oxygen species, thereby correcting the underlying hypoxia, ischemia, and edema seen in DR, as well as improving vascular function.

Conclusion

There is substantial unmet need for convenient, non-invasive treatments targeting moderately severe and severe NPDR to reduce progression and preserve vision. The existing pharmacotherapies (IVT corticosteroids and IVT anti-vascular endothelial growth factor-A) target inflammation and angiogenesis, respectively. Unlike these treatments, AOC3 inhibition is predicted to address the underlying hypoxia and ischemia seen in DR. AOC3 inhibitors represent a promising therapeutic strategy for treating patients with DR and could offer greater choice and reduce treatment burden, with the potential to improve patient compliance.

PARTICULATE MATTER FROM SYRINGES USED FOR INTRAVITREAL INJECTIONS

BACKGROUND

Syringes containing anti-vascular endothelial growth factor drugs to treat retinal diseases are prepared in different ways by various parties with syringe selection, preparation, and storage conditions affecting the risk of injecting particles into the vitreous. This study examines particle loads from various syringes over time.

METHODS

Four syringes were studied: two plastic transfer syringes lubricated with silicone oil or oleamide, a glass syringe with baked-on silicone, and a lubricant-free polymer syringe. Syringes were rinsed with water or filled with buffer and analyzed over time; particles were quantified by flow imaging. Particle formation in a bevacizumab formulation was also characterized.

RESULTS

Insulin syringes consistently showed very high particle counts. Oleamide-lubricated syringes had substantially fewer particles, but showed appreciable increases over time (leading to visible particles). Baked-on silicone glass syringes and lubricant-free polymer syringes both showed low particle levels ≥10 μm. Lubricant-free syringes showed the lowest particle levels ≥1 μm and the lowest particle levels with bevacizumab agitation.

CONCLUSION

Syringes have different intrinsic particle loads which can contribute to particle loads in the delivered drug. Oleamide-lubricated transfer syringes, commonly used for bevacizumab repackaging, have time-dependent particle loads and are associated with the formation of visible particles beyond 30 days of storage.

Container Closure and Delivery Considerations for Intravitreal Drug Administration

Intravitreal (IVT) administration of therapeutics is the standard of care for treatment of back-of-eye disorders. Although a common procedure performed by retinal specialists, IVT administration is associated with unique challenges related to drug product, device and the procedure, which may result in adverse events. Container closure configuration plays a crucial role in maintaining product stability, safety, and efficacy for the intended shelf-life. Careful design of primary container configuration is also important to accurately deliver small volumes (10-100 μL). Over- or under-dosing may lead to undesired adverse events or lack of efficacy resulting in unpredictable and variable clinical responses. IVT drug products have been traditionally presented in glass vials. However, pre-filled syringes offer a more convenient administration option by reducing the number of steps required for dose preparation there by potentially reducing the time demand on the healthcare providers. In addition to primary container selection, product development studies should focus on, among other things, primary container component characterization, material compatibility with the formulation, formulation stability, fill volume determination, extractables/leachables, and terminal sterilization. Ancillary components such as disposable syringes and needles must be carefully selected, and a detailed administration procedure that includes dosing instructions is required to ensure successful administration of the product. Despite significant efforts in improving the drug product and administration procedures, ocular safety concerns such as endophthalmitis, increased intraocular pressure, and presence of silicone floaters have been reported. A systematic review of available literature on container closure and devices for IVT administration can help guide successful product development.

Incidence of Acute Endophthalmitis After Intravitreal Bevacizumab Injection at a Tertiary Care Hospital in Lahore

OBJECTIVE

We aimed to assess the incidence, management, and visual outcome of acute endophthalmitis in patients following intravitreal bevacizumab injection in a tertiary care setup. It was a prospective and single-center database study.

PATIENTS AND METHODS

Patients receiving intravitreal bevacizumab injections for various retinal vascular diseases from January 2019 to September 2020. The study was carried out at the Institute of Ophthalmology, Mayo Hospital, Lahore over a period of 21 months. Preformed bevacizumab injections were administered intravitreally on patients of various retinal vascular diseases under strict aseptic measures and by following the standard guidelines. The patients were put on follow-ups for a duration of four weeks to see any signs of acute endophthalmitis.

RESULTS

A total of 3051 injections were administered in 1104 eyes of 743 patients during the above-mentioned study period. The incidence of endophthalmitis was found to be 0.0328% (1/3051). The patient, who developed endophthalmitis, was treated with topical and intravitreal antibiotics followed by vitrectomy that resulted in clinically significant improvement in vision.

CONCLUSION

Incidence of acute endophthalmitis following intravitreal bevacizumab injection was low and could be prevented by taking strict aseptic measures during administration.

Survey of Intravitreal Injection Techniques Among Retina Specialists in Mexico

Purpose

To report technique preferences for intravitreal injections among retina specialists in Mexico.

Methods

Cross-sectional survey. Ophthalmologists with a two-year retina training, active members of the Mexican Retina Association, were contacted through email to answer a survey consisting of 37 items regarding their IVI application technique.

Results

A total of 133 retina specialists participated, with a response rate of 78%. Forty-five percent applied the intravitreal injections in an operating room designated for the procedure. Sixty-three percent reported never injecting both eyes on the same day. Ninety-six percent wore a face mask during the procedure and 91% wore gloves. Eighty-two percent used a lid speculum. Tetracaine drops were the anesthetic method employed by 97% of participants. All participants utilized povidone-iodine for antisepsis. Eighty percent measured the puncture site with a caliper. Superotemporal quadrant was the one chosen to place the injection by 63% of participants. Fifty-nine percent indicated post-injection antibiotic drops for several days. Post-injection counting fingers visual acuity was verified by 53% of the participants. Fifty-six percent of the participants placed an eye-patch after the procedure.

Conclusion

There are different practices regarding the application of intravitreal injections among retina specialists in Mexico. Performing this type of survey periodically could show changes in preferences, as new evidence is incorporated into clinical practice.

The influence of dead spaces and the designs of injectors on the amount of drug dose in intra-vitreal injection

AIM

To evaluate the dead spaces resulting from different designs of the insulin injectors used for intravitreal injections and the amounts of drug doses.

METHODS

In the study, five different brands of sterile insulin injectors of 1 mL were used for the test. The weight of the injectors was determined before and after filling the injectors with 0.05 and 0.1 mL distilled water. The weight of the injectors was measured with and without the needle after the water within the injectors had been taken out and weight differences were measured. The difference between the intended amount of fluid to be thrown out and the weight of the fluid remaining in the injector was calculated as percent error.

RESULTS

After throwing out 0.05 mL distilled water from the injector, weights of the Beybi^®, Traf^®, Becton Dickinson^®, Ayset^®, and Setojet^® brands of injectors with 30 G needle were detected to increase the mean 0.0220 ± 0.006 g, 0.0208 ± 0.008 g, 0.0355 ± 0.016 g, 0.0219 ± 0.017 g, and 0.0150 ± 0.007 g, respectively compared to the weights of the dry injectors. The 0.1 mL injector group was found to be mean 0.0350 ± 0.014 g, 0.0264 ± 0.008 g, 0.0405 ± 0.015 g, 0.0272 ± 0.013 g, and 0.0245 ± 0.014 g, respectively. The maximum increase due to the dead spaces in the injectors was found in the Becton Dickinson^® injector, both in the 0.05 mL and the 0.1 mL groups (p < 0.000).

CONCLUSION

The injector designs may affect the dose of IVI required to be given. More correct amounts of drugs may be administered via the intra-vitreal route through designs that reduce the dead spaces at the end part of the injector and between the inner wall and the plunger.

Bioresorbable, Miniaturized Porous Silicon Needles on a Flexible Water-Soluble Backing for Unobtrusive, Sustained Delivery of Chemotherapy

Conventional melanoma therapies suffer from the toxicity and side effects of repeated treatments due to the aggressive and recurrent nature of melanoma cells. Less-invasive topical chemotherapies by utilizing polymeric microneedles have emerged as an alternative, but the sustained, long-lasting release of drug cargos remains challenging. In addition, the size of the microneedles is relatively bulky for the small, curvilinear, and exceptionally sensitive cornea for the treatment of ocular melanoma. Here, we report a design of bioresorbable, miniaturized porous-silicon (p-Si) needles with covalently linked drug cargos at doses comparable to those of conventional polymeric microneedles. The p-Si needles are built on a water-soluble film as a temporary flexible holder that can be intimately interfaced with the irregular surface of living tissues, followed by complete dissolution with saline solution within 1 min. Consequently, the p-Si needles remain embedded inside tissues and then undergo gradual degradation, allowing for sustained release of the drug cargos. Its utility in unobtrusive topical delivery of chemotherapy with minimal side effects is demonstrated in a murine melanoma model.