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Pharmaceutics
Special Issues
Ocular Drug Delivery Systems and Formulations
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Ocular Drug Delivery Systems and Formulations

A special issue of Pharmaceutics (ISSN 1999-4923). This special issue belongs to the section "Drug Delivery and Controlled Release".

Deadline for manuscript submissions: 27 April 2027 | Viewed by 5273

Editor

Dr. Victoria Díaz-Tomé

E-Mail Website
Guest Editor
1. Department of Pharmacology, Pharmacy and Pharmaceutical Technology, University of Santiago de Compostela (USC), 15705 Santiago de Compostela, Spain
2. Instituto de Investigação e Inovação em Saúde (i3S), Universidade do Porto, Porto, Portugal
Interests: drug delivery systems; pharmaceutics; nanoparticles; cyclodextrins; ophtalmic formulations
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Efficient drug delivery to ocular tissues remains a challenge due to the eye’s unique anatomical and physiological barriers. These barriers limit drug absorption, bioavailability, and therapeutic efficacy. In response, recent advances in the development of nanoscale drug delivery systems and novel biomaterials have opened new possibilities for targeted and sustained ocular therapies.

Innovative formulations—such as nanoparticles, liposomes, dendrimers, hydrogels, in situ gelling systems, and biodegradable implants, among others—offer enhanced drug stability, controlled release, prolonged residence time, and the ability to overcome conventional delivery limitations. These strategies enhance the penetration of therapeutic agents through ocular tissues, improving the treatment of different ocular structures, minimizing systemic absorption, and reducing potential side effects.

This Special Issue provides a comprehensive overview of recent advances in ocular drug delivery, focusing on cutting-edge formulations and delivery systems that are designed to overcome various ocular barriers.

By emphasizing the synergy between material science, pharmaceutical technology, and ocular biology, this Special Issue aims to inform and inspire future research toward more effective and patient-friendly ocular therapeutics.

Dr. Victoria Díaz-Tomé
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-anonymized peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Pharmaceutics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2900 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • ocular drug delivery
  • ophthalmic formulations
  • ophthalmic drug bioavailability
  • ophthalmic hydrogels
  • ophthalmic pharmaceutical nanotechnology
  • ocular therapies

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Published Papers (5 papers)

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Research

16 pages, 1274 KB  
Article
Stability Study of Meropenem 50 mg/mL Eye Drops in Polypropylene Dropper Bottles
by Juan Carlos Ruiz Ramirez, María Encarnación Martínez Madrid, Adrián Gómiz Sáez, Alice Charlotte Viney, José María Alonso Herreros and Pilar Almela Rojo
Pharmaceutics 2026, 18(8), 971; https://doi.org/10.3390/pharmaceutics18080971 - 7 Aug 2026
Abstract
Background/Objectives: Meropenem is a broad-spectrum carbapenem antibiotic with demonstrated efficacy against multidrug-resistant Gram-negative pathogens. Although its use as an ophthalmic formulation is off-label, growing clinical evidence supports its application in severe ocular infections such as keratitis and endophthalmitis. However, the intrinsic instability of [...] Read more.
Background/Objectives: Meropenem is a broad-spectrum carbapenem antibiotic with demonstrated efficacy against multidrug-resistant Gram-negative pathogens. Although its use as an ophthalmic formulation is off-label, growing clinical evidence supports its application in severe ocular infections such as keratitis and endophthalmitis. However, the intrinsic instability of meropenem in aqueous solutions and the absence of standardized ophthalmic preparations limit its routine use. Furthermore, no stability studies are currently available for meropenem 50 mg/mL eye drops stored in polypropylene (PP) dropper bottles under freezing and subsequent refrigerated conditions. The aim of this study was to evaluate the physicochemical and microbiological stability of a 50 mg/mL meropenem ophthalmic solution prepared in a hospital pharmacy using a commercial meropenem pharmaceutical product, and packaged in PP containers. Methods: Eye drops were aseptically prepared from a commercially available pharmaceutical product, containing 1g de meropenem and anhydrous sodium carbonate as an excipient. After preparation, the drops were stored at −20 ± 2 °C for up to 42 days, followed by refrigerated storage (5 ± 3 °C) after thawing for up to 7 days. Chemical stability was assessed using a validated stability-indicating HPLC method in accordance with ICH guidelines and was defined as 90–110% recovery of the initial concentration. Physical stability (appearance, pH, particulate matter) and microbiological stability were also evaluated under simulated in-use conditions. Results: The HPLC method demonstrated excellent linearity, precision, and accuracy. Meropenem concentrations remained within the predefined acceptance limits throughout the 42-day study period under freezing conditions, with no significant changes in pH, color, or particulate formation. After thawing, a progressive decrease in drug concentration was observed under refrigerated conditions, falling below 90% of the initial concentration within 24–48 h. A concomitant color change from colorless to yellow was also detected, consistent with β-lactam ring hydrolysis. Despite this degradation, no significant changes in physical parameters other than color were observed, and microbiological testing confirmed sterility for up to 7 days under refrigerated conditions. Conclusions: Meropenem drops 50 mg/mL in PP dropper bottles are physicochemically and microbiologically stable for 43 days (42 days under frozen conditions plus 1 day, in-use conditions, after opening and under refrigeration). Full article
(This article belongs to the Special Issue Ocular Drug Delivery Systems and Formulations)
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23 pages, 17391 KB  
Article
Metformin and cRGDfc-Modified Nanoparticles Loaded with Curcumin for Age-Related Macular Degeneration: In Vitro Pharmacodynamics and Molecular Mechanisms
by Juan Liu, Ziheng Wang, Yuchang Yang, Lisha Yi, Shiman Li, Jingyi Gao, Jia Zhou, Nannan Cheng, Xingbin Yin, Xiaoxv Dong, Jian Ni and Changhai Qu
Pharmaceutics 2026, 18(6), 761; https://doi.org/10.3390/pharmaceutics18060761 - 22 Jun 2026
Viewed by 567
Abstract
Objectives: This study aimed to develop curcumin nanoparticles (Cur@PCL-PEG-MF/cRGDfc) with retinal-targeting capability and to evaluate their biological effects and pharmacological mechanisms in vitro. Methods: After synthesis of the carrier framework, metformin (MF) and cRGDfc were conjugated to the carrier material using the carbodiimide [...] Read more.
Objectives: This study aimed to develop curcumin nanoparticles (Cur@PCL-PEG-MF/cRGDfc) with retinal-targeting capability and to evaluate their biological effects and pharmacological mechanisms in vitro. Methods: After synthesis of the carrier framework, metformin (MF) and cRGDfc were conjugated to the carrier material using the carbodiimide method and Michael addition reaction, respectively. Subsequently, self-assembled nanoparticles were formed from the carrier and curcumin under specific conditions. The materials were characterized by spectroscopy, chromatography, elemental analysis, energy-dispersive spectroscopy and X-ray diffraction. The efficacy of the formulation was evaluated in two cell lines, ARPE-19 and HUVEC-T1. In addition, the pharmacological mechanism was explored using transcriptome sequencing as a complementary approach. Key Findings: Self-assembled nanoparticles were successfully prepared by combining the two modified carrier materials, PCL-PEG-MF and PCL-PEG-cRGDfc, with curcumin. The nanoparticles exhibited an encapsulation efficiency of 78.09%, a particle size of 162.33 nm, and a zeta potential of −23.28 mV and displayed a spherical morphology. They showed sustained release in simulated physiological conditions and stronger affinity for ARPE-19 cells under oxidative stress. Nearly 100% of the nanoparticles were internalized by the cells, which was accompanied by reduced ROS and LDH release and decreased DNA fragmentation. In addition, the nanoparticles inhibited neovascularization by reducing VEGF-A release, thereby potentially protecting the retina in macular degeneration and reducing choroidal hemorrhage. Further analyses showed that curcumin and its nanoformulations significantly reduced the expression of inflammatory factors such as IL-1β and IL-18, lowered the protein levels of Caspase-1, GSDMD-N, and NLRP3, and increased AMPK levels. Conclusions: Using PCL-PEG as the carrier framework, MF and cRGDfc were conjugated to construct a curcumin-loaded nanoparticle with retinal-targeting capability. This nanoparticle, characterized by a small particle size, sustained release, and targeted delivery to retinal pigment epithelium (RPE) cells under oxidative stress, alleviated oxidative stress-induced damage. Its therapeutic effect may be mediated, at least in part, by interference with the AMPK/mTOR pathway and activation of the NLRP3/Caspase-1/GSDMD pathway. Full article
(This article belongs to the Special Issue Ocular Drug Delivery Systems and Formulations)
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24 pages, 1769 KB  
Article
Micelle-Based Ocular Inserts for Sustained Delivery and Improved Corneal Permeation of Rebamipide in Dry Eye Disease
by Yashkumar Patel, Ketan M. Ranch, Anilkumar Prajapati, Harshilkumar Jani, Julalak Chorachoo Ontong and Sudarshan Singh
Pharmaceutics 2026, 18(5), 578; https://doi.org/10.3390/pharmaceutics18050578 - 7 May 2026
Viewed by 1190
Abstract
Background: Rebamipide (REB) is a poorly water-soluble drug with limited ocular bioavailability, necessitating advanced delivery strategies for sustained therapy in dry eye disease. Methods: In the present study, micelle-assisted ocular inserts were developed using non-ionic surfactants to enhance REB solubilization, drug loading, and [...] Read more.
Background: Rebamipide (REB) is a poorly water-soluble drug with limited ocular bioavailability, necessitating advanced delivery strategies for sustained therapy in dry eye disease. Methods: In the present study, micelle-assisted ocular inserts were developed using non-ionic surfactants to enhance REB solubilization, drug loading, and controlled ocular delivery. The intrinsic solubility of REB in simulated tear fluid (STF, pH 7.4) was evaluated and compared with micellar systems. The formulations were characterized for particle size, polydispersity index, and zeta potential. Ocular inserts were fabricated via UV photopolymerization and evaluated for physicochemical properties, drug content, in vitro drug release, ex vivo permeation, cytocompatibility using SIRC cells, and histopathological analysis. Results: REB exhibited low intrinsic solubility in STF (26.05 ± 1.00 µg/mL), which was significantly enhanced in micellar systems, particularly with Solutol HS 15 (306.71 ± 1.10 µg/mL) and Tween 80 (263.18 ± 1.19 µg/mL). All micellar formulations formed stable nanosized micelles (7.5–15.1 nm) with low polydispersity (PDI < 0.35) and near-neutral zeta potential (−0.08 to −2.81 mV). The prepared ocular inserts showed uniform thickness, weight, and physiological surface pH. Micelle-assisted inserts demonstrated significantly higher drug content (87.40 ± 3.25 to 99.19 ± 2.44 µg/insert) compared to plain REB inserts (21.41 ± 2.28 µg/insert). In- vitro studies revealed sustained drug release over 24 h (92.25 ± 1.64 to 100.50 ± 1.10%), whereas plain inserts showed burst release. Ex vivo permeation studies indicated enhanced drug permeation (up to 77.30 ± 0.34 µg) and improved flux (1.38–8.52 µg/cm2·h) compared to plain REB. Cytocompatibility studies confirmed >90% SIRC cell viability, and histopathological analysis showed no structural damage to corneal tissue. Conclusions: Micelle-assisted ocular inserts, particularly those formulated with Solutol HS 15 and Tween 80, provide a promising platform for sustained, safe, and effective ocular delivery of Rebamipide in the management of dry eye disease. Full article
(This article belongs to the Special Issue Ocular Drug Delivery Systems and Formulations)
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19 pages, 2686 KB  
Article
Development of Autologous Serum Ocular Insert for Chronic Dry Eye Disease
by Hend Abdelmohsen, Ahmad Chaudhry, Vishal Jhanji and Morgan V. DiLeo
Pharmaceutics 2026, 18(2), 267; https://doi.org/10.3390/pharmaceutics18020267 - 21 Feb 2026
Viewed by 1118
Abstract
Background: Dry eye disease is a multifactorial disease of the ocular surface and/or tear film. It is one of the leading causes of ocular morbidity worldwide. Current therapy primarily consists of topical application of artificial tears and anti-inflammatory drugs. Autologous serum eye drops [...] Read more.
Background: Dry eye disease is a multifactorial disease of the ocular surface and/or tear film. It is one of the leading causes of ocular morbidity worldwide. Current therapy primarily consists of topical application of artificial tears and anti-inflammatory drugs. Autologous serum eye drops are an alternative treatment typically reserved for severe dry eyes mainly due to the limitations associated with access, storage, and the need for frequent application. Methods: Herein we describe the design and characterization of a bilayer carboxymethylcellulose/serum ocular insert that may expand the utility and accessibility of this treatment method. The insert, designed to be placed in the inferior fornix of the eye, has a unique carboxymethylcellulose backing layer to enhance comfort and direct protein release to the ocular surface. Results: Released serum proteins were able to protect corneal cells in vitro after treatment with hydrogen peroxide, demonstrated by a significantly higher cell viability compared to both serum eye drops and untreated cells. Our in vivo studies showed that the ocular inserts were able to deliver epitheliotrophic growth factors to treated animals at a level similar to standard serum eyedrops at an 8-fold reduction in dosing frequency that was well-tolerated in the treated eyes. In comparison to the control, serum ocular inserts demonstrated improvement in dry eye signs and symptoms in a rabbit model. Conclusions: Our results demonstrate that the novel inserts prolong the delivery of key proteins and growth factors for treating dry eye disease and significantly enhance shelf stability. Full article
(This article belongs to the Special Issue Ocular Drug Delivery Systems and Formulations)
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27 pages, 16394 KB  
Article
Sustained Intraocular Pressure Reduction Using Bisoprolol-Loaded PLGA Nanoparticles: A Promising Strategy for Enhanced Ocular Delivery with Reduced GFAP Expression Indicative of Lower Glial Activation
by Sammar Fathy Elhabal, Omnia Mohamed Mahfouz, Mohamed Fathi Mohamed Elrefai, Mahmoud H. Teaima, Ahmed Abdalla and Mohamed El-Nabarawi
Pharmaceutics 2025, 17(11), 1418; https://doi.org/10.3390/pharmaceutics17111418 - 31 Oct 2025
Cited by 10 | Viewed by 1477
Abstract
Background/Objectives: Glaucoma is a neurodegenerative optic disorder which occurs due to persistent elevation of the intraocular pressure. It leads to permanent blindness and currently affects over 75 million individuals worldwide. Nowadays, topical ocular medications are the leading therapy despite their poor ocular [...] Read more.
Background/Objectives: Glaucoma is a neurodegenerative optic disorder which occurs due to persistent elevation of the intraocular pressure. It leads to permanent blindness and currently affects over 75 million individuals worldwide. Nowadays, topical ocular medications are the leading therapy despite their poor ocular penetration and short residence time. Methods: The purpose of this research is to formulate bisoprolol hemifumarate-loaded polylactic-co-glycolic acid (PLGA) nanoparticles and improve their ocular penetration and bioavailability for the treatment of glaucoma by enhancing the delivery of the drug to the posterior part of eye. By using the solvent displacement method, formulations were prepared and optimum formula was elected using Design-Expert® software. Results: In vitro characterization demonstrated that the optimum formula contained 25 mg BSP, 22.5 mg PLGA, and 60 mg Tween80, yielding high values of drug encapsulation (75%) and zeta potential (−18.7 ± 0.41 mV), with a low particle size (105 ± 0.35 nm) and polydispersity index (0.411 ± 0.71). Transmission electron microscopy and atomic force microscopy showed smooth and spherical nanosized particles. X-ray diffraction, differential scanning calorimetry, and Fourier-transform infrared spectroscopy revealed successful encapsulation of the drug inside the polymeric matrix. Ex vivo confocal laser scanning microscopy proved that there was better uptake of the drug upon using PLGA-NPs. In vitro release profiles indicated biphasic drug release from the PLGA-NPs, confirming a sustained drug release over 12 h. In vivo studies showed that BSP-PLGA-NPs significantly reduced the IOP compared to bisoprolol solution. Quantitative immunohistochemistry showed lower retinal GFAP expression with BSP-PLGA-NPs compared with induced controls and drug solution, which is indicative of attenuated glial activation. Conclusions: These data support improved ocular delivery and an improved pharmacodynamic effect; however, they demonstrate association rather than a direct mechanistic suppression of glial pathways. Full article
(This article belongs to the Special Issue Ocular Drug Delivery Systems and Formulations)
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