Biocompatibility Assessment of Potential Materials for Use in an Ophthalmic Drug Delivery Device

Glaucoma is a chronic optic neuropathy that affects an estimated 70 million people worldwide of which 7 million are blind. The only proven modifiable risk factor is raised intra-ocular pressure (IOP) and treatment to reduce IOP can be in the form of eye drops, laser or surgery. Scarring and the development of fibrous encapsulation at the surgical site complicate glaucoma surgery. Development of a drug delivery platform to modulate the wound healing response may improve surgical outcomes. Potential materials include hydrogels, three-dimensional cross-linked networks of water-soluble polymers, as well as 3D printed resins that are an increasingly popular approach for rapid prototyping and manufacture. The aim of this thesis was to assess the in vitro biocompatibility of 3D printed and phosphorylcholine (PC) based materials compared to materials used in current ophthalmic devices including polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), silicone, 2-hydroxyethyl methacrylate (HEMA). Sterility testing was performed using ethanol and autoclaving processes. Adhesion of monocytes, macrophages and fibroblasts to material surfaces was assessed using various assays and fluorescent microscopy. Adsorption of albumin and fibrinogen was assessed using SDS Page gel electrophoresis, UV photospectrometry, fluorescein isothiocyanate labelled bovine serum albumin (FITC-BSA) and micro bicinchoninic acid (BCA) techniques. It was observed that PC based materials demonstrated less cellular and protein adhesion than materials used in current ophthalmic devices but more than a contact lens of similar composition suggesting that the manufacturing process may play a role in the biocompatibility response. Similar levels of cell adhesion and protein adsorption were observed between 3D printed materials and materials used in current ophthalmic devices, but cytotoxicity is a potential concern and further testing is warranted. Our results demonstrate that PC hydrogels and 3D printed materials can potentially be used in drug delivery devices to treat ophthalmic conditions. Future work will focus on optimising the device design, hydrogel formulation and ultimately assessing biocompatibility response in an in vivo setting

Development of a novel biocompatible drug delivery platform for ophthalmic conditions

Glaucoma is a chronic optic neuropathy that affects an estimated 70 million people worldwide of which 7 million are blind. It is the number one cause of irreversible blindness and the only proven modifiable risk factor is raised intra-ocular pressure (IOP). Glaucoma treatment aims to reduce IOP and can be in the form of eye drops, laser or surgery. Surgery aims to increase outflow mechanism for drainage of aqueous humour from the anterior chamber. This can be in the form of glaucoma filtration surgery (GFS) or insertion of a glaucoma drainage device (GDD). GFS is complicated by scarring in the post-operative period and GDD surgery insertion is complicated by the development of a fibrous encapsulation around the device. This encapsulation initially acts as a flow control mechanism but subsequently results in device failure. Factors that may influence this include: the material surface quality, the shape of the device and the device material. 2-methacryloyloxyethyl (MPC) is used as a synthetic polymer based coating that has been demonstrated to prevent the occurrence of coronary artery stenosis. The aim of this investigation was to assess the in vitro biocompatibility of 3D printed and PC based materials compared to materials used in current ophthalmic devices. Sterility testing was performed using ethanol and autoclaving processes, commonly used techniques for the development of ophthalmic devices. Adhesion of monocytes, macrophages and fibroblasts to material surfaces was assessed using live stain, Alamar Blue and CyQUANT assays and fluorescent microscopy. Adsorption of albumin and fibrinogen was assessed using SDS Page Gel Electrophoresis, UV Photospectrometry, Fluorescein Isothiocyanate Labelled Bovine Serum Albumin (FITC-BSA) and Micro Bicinchoninic Acid (BCA) techniques. PC based materials (containing 5 and 15% MPC) were compared to Polytetrafluoroethylene (PTFE), Polyethylene Terephthalate (PET), Polymethyl Methacrylate (PMMA), Silicone, 2-hydroxyethyl methacrylate (HEMA) and a contact lens that contains 15% MPC. It was observed that PC based materials demonstrated less cellular and protein adhesion than materials used in current ophthalmic devices but more than a contact lens of similar composition. This suggests that the manufacturing process may play a role in the biocompatibility response and these studies were therefore repeated with different contact lenses based on the Food & Drug Administration (FDA) grouping of contact lenses. PC is a potential material that can be used to improve biocompatibility of ophthalmic devices. Future work will be performed to develop a novel drug delivery platform that can be used in the treatment of ophthalmic conditions

Somatostatin Analogs Modulate AIP in Somatotroph Adenomas: The Role of the ZAC1 Pathway

CONTEXT: Somatotroph adenomas harboring aryl hydrocarbon receptor interacting protein (AIP) mutations respond less well to somatostatin analogs, suggesting that the effects of somatostatin analogs may be mediated by AIP. OBJECTIVE: The objective of the investigation was to study the involvement of AIP in the mechanism of effect of somatostatin analogs. DESIGN: In the human study, a 16-wk somatostatin analog pretreatment compared with no pretreatment. In the in vitro cell line study, the effect of somatostatin analog treatment or small interfering RNA (siRNA)/plasmid transfection were studied. SETTING: The study was conducted at a university hospital. PATIENTS: Thirty-nine sporadic and 10 familial acromegaly patients participated in the study. INTERVENTION: Interventions included preoperative lanreotide treatment and pituitary surgery. OUTCOME: For the human study, GH and IGF-I levels, AIP, and somatostatin receptor staining were measured. For the cell line, AIP and ZAC1 (zinc finger regulator of apoptosis and cell cycle arrest) expression, metabolic activity, and clone formation were measured. RESULTS: Lanreotide pretreatment reduced GH and IGF-I levels and tumor volume (all P < 0.0001). AIP immunostaining was stronger in the lanreotide-pretreated group vs. the surgery-only group (P < 0.001). After lanreotide pretreatment, the AIP score correlated to IGF-I changes in females (R = 0.68, P < 0.05). Somatostatin receptor staining was not reduced in samples with AIP mutations. In GH3 cells, 1 nm octreotide increased AIP mRNA and protein (both P < 0.01) and ZAC1 mRNA expression (P < 0.05). Overexpression of wild-type (but not mutant) AIP increased ZAC1 mRNA expression, whereas AIP siRNA knockdown reduced ZAC1 mRNA (both P < 0.05). The siRNA-mediated knockdown of AIP led to an increased metabolic activity and clonogenic ability of GH3 cells compared with cells transfected with a nontargeting control (both P < 0.001). CONCLUSION: These results suggest that AIP may play a role in the mechanism of action of somatostatin analogs via ZAC1 in sporadic somatotroph tumors and may explain their lack of effectiveness in patients with AIP mutations