Mohamed Moustafa Ibrahim

Background: Glaucoma is a multifactorial optic neuropathy characterized by progressive retinal ganglion cell (RGC) loss, in which both intraocular pressure (IOP)-dependent and -independent mechanisms contribute to disease progression. Gabapentinoids target α2δ subunits of voltage-gated calcium channels (VGCCs), which regulate calcium-dependent processes relevant to both aqueous humor dynamics and retinal neuronal function. This systematic review evaluates heterogeneous evidence relevant to α2δ modulation of IOP regulation, retinal neuroprotection, and associated molecular and synaptic pathways. Methods: A systematic literature search was conducted across PubMed, Embase, Scopus, and Cochrane Library databases from inception. Studies investigating gabapentinoids or α2δ subunit modulation with outcomes related to IOP, RGC survival, or relevant molecular signaling were included. Risk of Bias (RoB) was assessed using the OHAT rating tool, and Certainty of Evidence (CoE) was rated on the GRADE four-level scale using initial confidence criteria from the OHAT approach. Due to heterogeneity in study design and outcomes, findings were synthesized narratively, with included studies divided and assessed separately within anterior segment pharmacology, anterior segment genetics, neuroprotection, and mechanistic bodies of evidence. Results: Of 1973 unique records screened, 11 studies met inclusion criteria, which were further subdivided into 15 experimental arms according to evidence type. Distinct evidence bodies were anterior segment pharmacology (5 study arms), anterior segment genetics (3 study arms), neuroprotection (4 study arms), and mechanistic (3 study arms). Across mouse and rabbit models of spontaneous ocular hypertension, topical pregabalin (PRG) consistently reduced IOP in a dose-dependent manner, with peak effects generally occurring 1.5–5 h after administration depending on strain and formulation. Plateaus in maximal IOP reduction were observed at 0.9% PRG solution in mice and 0.6–0.7% PRG microemulsion (ME) in rabbits. ME formulations of PRG consistently prolonged duration of action and increased cumulative exposure relative to non-ME PRG formulations. PRG ME achieved maximal IOP reduction comparable to that of 0.005% latanoprost solution while retaining their increased duration of action and cumulative exposure. Repeated once-daily PRG ME dosing maintained IOP-lowering responses over 21- and 60-day treatment periods. Genetic studies separately associated CACNA2D1/Cacna2d1 with IOP-related phenotypes and primary open-angle glaucoma susceptibility, providing target-level evidence. Preclinical posterior segment studies reported retinal structural preservation or improved RGC survival with PRG, while separate studies of GBP-L demonstrated RGC-survival effects associated with K-ATP channel activity rather than established α2δ modulation. Mechanistic studies separately identified thrombospondin-2 (TSP2)-α2δ1 signaling as a mediator of injury-associated synaptic remodeling, with pharmacologic disruption attenuating synaptic protein upregulation and improving axonal integrity. RoB varied across study arms and bodies of evidence. Anterior pharmacology included five Tier II study arms, anterior genetics included two Tier I arms and one Tier II arm, and all neuroprotection and mechanistic arms were Tier II. CoE was rated moderate for both anterior pharmacology and genetics, and low for both neuroprotection and mechanistic evidence. Conclusions: The available evidence is predominantly preclinical and heterogeneous. Moderate certainty within the defined anterior segment evidence body reflects consistency of the reported preclinical effect and does not establish clinical efficacy or independent reproducibility, as the topical PRG intervention literature is concentrated within a single investigative group. The neuroprotective and mechanistic findings remain hypothesis-generating and do not establish a unified mechanism or simultaneous IOP-lowering and neuroprotective action. Independent pharmacologic replication, validation in chronic glaucomatous neurodegeneration models, and long-term topical safety evaluation are prerequisites to discussions of clinical relevance.

Background/Objectives: Despite available treatment options, glaucoma continues to be a leading cause of irreversible blindness. Current medications have multiple limitations, including rapid drainage, ocular irritation, requirement for multiple daily dosings, and systemic side effects. The current study was designed to engineer and characterize a pregabalin-containing enhanced delivery formulation (PRG-EDF) to directly address these inadequacies. Methods: PRG-EDF eye drops were prepared using ingredients that are either U.S. Food and Drug Administration (FDA)-approved for ophthalmic use or have established safety profiles. The formulation was characterized using multiple evaluations, including pH, zetasizer analyses, viscosity, in vitro drug release, transcorneal permeability, determination of dose concentration and volume, systemic exposure, and potential for tachyphylaxis. Efficacy was evaluated using both Dutch belted rabbits and baboons. Results: PRG-EDF provides extended release for up to 24 h. Ex vivo data reveal that PRG-EDF does not alter the inherent high PRG corneal permeability. An intraocular pressure (IOP) study using DB rabbits demonstrates that 40 µL of PRG-EDF, 0.6%, is the optimum dose of our formulation. Comparison of the efficacy of PRG-EDF with commercial products demonstrated its superiority in overall IOP-lowering efficacy. An extended in vivo assessment demonstrated that the potency of PRG-EDF reached maximum IOP-lowering amplitude after 4 weeks of daily dosing. Moreover, an in vivo bioadhesion assay demonstrated that EDF remained on the ocular surface for up to 24 h. Impressively, PRG-EDF is as effective in baboons as in rabbits. Conclusions: We have successfully engineered a highly promising once-daily glaucoma medication with superior efficacy, as illustrated by higher IOP-lowering ability and prolonged duration of action.

Background/Objectives: Glaucoma is a multifactorial eye disease that can cause optic nerve damage and irreversible blindness. It is considered a significant public health problem worldwide. Topical intraocular pressure (IOP)-lowering eye preparations are used to prevent or slow further damage. Previously, we demonstrated that nimodipine (NMD), a calcium channel blocker, significantly reduced IOP after a single drop of NMD/HPMC suspension. The current study was designed to develop NMD chitosan nanoparticles (NMD-CS NPs) to improve the NMD IOP-lowering efficacy. Methods: NMD-CS NPs were prepared using the spontaneous-emulsification solvent diffusion method. Three different types of chitosan, carboxymethyl CS (CMCS), low molecular weight CS (LCS), and medium molecular weight CS (MCS), were used. Different concentrations of polymers, various stabilizers, and two pHs were used for formulation optimization. NMD-CS NPs were characterized regarding their particle size, polydispersity index (PDI), zeta potential, DSC, FTIR, and encapsulation efficiency. NMD-CS NPs were incorporated into eye drops and characterized in terms of their in vitro release, cytotoxicity, transcorneal permeability, and in vivo efficacy. Results: The optimized NMD-CS NPs demonstrate a small particle size with a narrow size distribution and acceptable zeta potential values. DSC and FTIR results confirmed the complete entrapment of NMD inside the NPs. NMD-CS NP eye drops successfully sustained NMD release without any burst effect. These NPs demonstrated a Higuchi non-Fickian diffusion mechanism and 79.41% improved corneal permeability. Cytotoxicity studies revealed that NMD formulations are nontoxic. After a single topical ocular application, NMD-MCS NP eye drops induced a significantly superior effect to Timolol maleate eye drops with regard to the %IOP reduction and duration of action. Conclusions: Evaluation results of NMD-CS NP eye drops show their positive effect in a preclinical animal model as a promising glaucoma therapy.

Periodontitis and severe trauma are major causes of damage to the periodontal ligament (PDL). Repairing the native conditions of the PDL is essential for the stability of the tissue and its interfaces. Bioprinting periodontal ligament stem cells (PDLSCs) is an interesting approach to guide the regeneration of PDL and interfacial integration. Herein, a collagen-based bioink mimicking the native extracellular matrix conditions and carrying PDLSCs was tested to guide the periodontal ligament organization. The bioink was tested at two different concentrations (10 and 15 mg/mL) and characterized by swelling and degradation, microstructural organization, and rheological properties. The biological properties were assessed after loading PDLSCs into bioinks for bioprinting. The characterization was performed through cell viability, alizarin red assay, and expression for ALP, COL1A1, RUNX2, and OCN. The in vivo biocompatibility of the PDLSC-laden bioinks was verified using subcutaneous implantation in mice. Later, the ability of the bioprinted PDLSC-laden bioinks on dental root fragments to form PDL was also investigated in vivo in mice for 4 and 10 weeks. The bioinks demonstrated typical shear-thinning behavior, a porous microstructure, and stable swelling and degradation characteristics. Both concentrations were printable and provided suitable conditions for a high cell survival, proliferation, and differentiation. PDLSC-laden bioinks demonstrated biocompatibility in vivo, and the bioprinted scaffolds on the root surface evidenced PDLSC alignment, organization, and PDLSC migration to the root surface. The versatility of collagen-based bioinks provides native ECM conditions for PDLSC proliferation, alignment, organization, and differentiation, with translational applications in bioprinting scaffolds for PDL regeneration.

Skin melanoma is considered the most dangerous form of skin cancer due to its association with high risk of metastasis, high mortality rate and high resistance to different treatment options. Genistein is a natural isoflavonoid with known chemotherapeutic activity. Unfortunately, it has low bioavailability due to its poor aqueous solubility and excessive metabolism. In the current study, genistein was incorporated into transferosomal hydrogel to improve its bioavailability. The prepared transferosomal formulations were characterized regarding: particle size; polydispersity index; zeta potential; encapsulation efficiency; TEM; FTIR; DSC; XRD; in vitro drug release; viscosity; pH; ex vivo anti-tumor activity on 3D skin melanoma spheroids and 1-year stability study at different storage temperatures. The optimized formulation has high encapsulation efficiency with an excellent particle size that will facilitate its penetration through the skin. The transfersomes have a spherical shape with sustained drug release profile. The anti-tumor activity evaluation of genistein transfersome revealed that genistein is a potent chemotherapeutic agent with enhanced penetration ability through the melanoma spheroids when incorporated into transfersomes. Stability study results demonstrate the high physical and chemical stability of our formulations. All these outcomes provide evidence that our genistein transferosomal hydrogel is a promising treatment option for skin melanoma.

Glaucoma is a leading cause of permanent vision loss and current drugs do not halt disease progression. Thus, new therapies targeting different drug targets with novel mechanisms of action are urgently needed. Previously, we identified CACNA2D1 as a novel modulator of intraocular pressure (IOP) and demonstrated that a topically applied CACNA2D1 antagonist—pregabalin (PRG)—lowered IOP in a dose-dependent manner. To further validate this novel IOP modulator as a drug target for IOP-lowering pharmaceutics, a homology model of CACNA2D1 was built and docked against the NCI library, which is one of the world’s largest and most diverse compound libraries of natural products. Acivicin and zoledronic acid were identified using this method and together with PRG were tested for their plausible IOP-lowering effect on Dutch belted rabbits. Although they have inferior potency to PRG, both of the other compounds lower IOP, which in turn validates CACNA2D1 as a valuable drug target in treating glaucoma.

Corneal penetration is a key rate limiting step in the bioavailability of topical ophthalmic formulations that incorporate poorly permeable drugs. Recent advances have greatly aided the ocular delivery of such drugs using colloidal drug delivery systems. Ribavirin, a poorly permeable BCS class-III drug, was incorporated in bioadhesive multiple W/O/W microemulsion (ME) to improve its corneal permeability. The drug-loaded ME was evaluated regarding its physical stability, droplet size, PDI, zeta potential, ultrastructure, viscosity, bioadhesion, in vitro release, transcorneal permeability, cytotoxicity, safety and ocular tolerance. Our ME possessed excellent physical stability, as it successfully passed several cycles of centrifugation and freeze–thaw tests. The formulation has a transparent appearance due to its tiny droplet size (10 nm). TEM confirmed ME droplet size and revealed its multilayered structure. In spite of the high aqueous solubility and the low permeability of ribavirin, this unique formulation was capable of sustaining its release for up to 24 h and improving its corneal permeability by 3-fold. The in vitro safety of our ME was proved by its high percentage cell viability, while its in vivo safety was confirmed by the absence of any sign of toxicity or irritation after either a single dose or 14 days of daily dosing. Our ME could serve as a vehicle for enhanced ocular delivery of drugs with different physicochemical properties, including those with low permeability.

Elevated intraocular pressure (IOP) is the most significant risk factor contributing to visual field loss in glaucoma. Unfortunately, the deficiencies associated with current therapies have resulted in reduced efficacy, several daily dosings, and poor patient compliance. Previously, we identified the calcium voltage-gated channel auxiliary subunit alpha2delta 1 gene (Cacna2d1) as a modulator of IOP and demonstrated that pregabalin, a drug with high affinity and selectivity for CACNA2D1, lowered IOP in a dose-dependent manner. Unfortunately, IOP returned to baseline at 6 h after dosing. In the current study, we develop a once daily topical pregabalin-loaded multiple water-in-oil-in-water microemulsion formulation to improve drug efficacy. We characterize our formulations using multiple in vitro and in vivo evaluations. Our lead formulation provides continuous release of pregabalin for up to 24 h. Because of its miniscule droplet size (30 h post-application. Although there were no significant differences in the amplitude of IOP reduction between the formulations we tested, a significant difference was clearly observed in their duration of action. Our multilayered microemulsion is a promising carrier that sustains the release and prolongs the duration of action of pregabalin, a proposed glaucoma therapeutic.

Primary open angle glaucoma (POAG) is the most common glaucoma type worldwide. The most significant risk factor of this type of glaucoma is the increased intraocular pressure (IOP) that may result in optic nerve damage and gradual but complete loss of vision. Reduction of IOP is the most important measure that should be taken into consideration during selection of glaucoma therapy. Several IOP-lowering medications are available in the drug market. Unfortunately, most of them associated with severe local and/or systemic adverse effects, short duration of action and poor patient compliance. In the current research we strive to develop a long acting, once daily, nanoparticle (NP)-based, ocular formulation loaded with R-801 (a newly discovered drug). Our NPs were prepared from carefully selected bioadhesive and biocompatible materials using double emulsification solvent diffusion method. This method of preparation was selected to obtain the highest encapsulation efficiency for our water-soluble drug and the smallest particle size for our NPs. Also, the NPs were incorporated in biocompatible and bioadhesive vehicles to achieve the required safety, biocompatibility and prolonged corneal contact time. Our formulations were subjected to various in vitro and in vivo evaluations that demonstrated their safety and ability to sustain the drug release, prolong corneal contact time, lower IOP in different animal models, and maintain the IOP at almost constant low value through the day without any fluctuation upon long-term daily application.

Short precorneal residence time and poor transocular membrane permeability are the major challenges associated with topical ocular drug delivery. In the present research, the efficiency of the electrolyte-triggered sol-to-gel–forming system of natamycin (NT) transfersomes was investigated for enhanced and prolonged ophthalmic delivery. Transfersomes were optimized by varying the molar ratios of phospholipid, sorbitan monostearate (Span) and tocopheryl polyethylene glycol succinate (TPGS). NT transfersome formulations (FNs) prepared with a 1:1 molar ratio of phospholipid-to-Span and low levels of TPGS showed optimal morphometric properties, and were thus selected to fabricate the in situ gelling system. Gellan gum–based (0.3% w/v) FN-loaded formulations (FNGs) immediately formed an in situ gel in the simulated tear fluid, with considerable viscoelastic characteristics. In vitro cytotoxicity in corneal epithelial cells and corneal histology studies demonstrated the ocular safety and cytocompatibility of these optimized formulations. Transcorneal permeability of NT from these formulations was significantly higher than in the control suspension. Moreover, the ocular disposition studies of NT, from the FNs and FNGs, in New Zealand male albino rabbits demonstrated the superiority of the electrolyte-sensitive FNGs in terms of NT delivery to the ocular tissues.