Fabrication and Characterization of an Enzyme-Triggered, Therapeutic-Releasing Hydrogel Bandage Contact Lens Material

PURPOSE

The purpose of this study was to develop an enzyme-triggered, therapeutic-releasing bandage contact lens material using a unique gelatin methacrylate formulation (GelMA+).

METHODS

Two GelMA+ formulations, 20% w/v, and 30% w/v concentrations, were prepared through UV polymerization. The physical properties of the material, including porosity, tensile strain, and swelling ratio, were characterized. The enzymatic degradation of the material was assessed in the presence of matrix metalloproteinase-9 (MMP-9) at concentrations ranging from 0 to 300 µg/mL. Cell viability, cell growth, and cytotoxicity on the GelMA+ gels were evaluated using the AlamarBlueTM assay and the LIVE/DEADTM Viability/Cytotoxicity kit staining with immortalized human corneal epithelial cells over 5 days. For drug release analysis, the 30% w/v gels were loaded with 3 µg of bovine lactoferrin (BLF) as a model drug, and its release was examined over 5 days under various MMP-9 concentrations.

RESULTS

The 30% w/v GelMA+ demonstrated higher crosslinking density, increased tensile strength, smaller pore size, and lower swelling ratio (p < 0.05). In contrast, the 20% w/v GelMA+ degraded at a significantly faster rate (p < 0.001), reaching almost complete degradation within 48 h in the presence of 300 µg/mL of MMP-9. No signs of cytotoxic effects were observed in the live/dead staining assay for either concentration after 5 days. However, the 30% w/v GelMA+ exhibited significantly higher cell viability (p < 0.05). The 30% w/v GelMA+ demonstrated sustained release of the BLF over 5 days. The release rate of BLF increased significantly with higher concentrations of MMP-9 (p < 0.001), corresponding to the degradation rate of the gels.

DISCUSSION

The release of BLF from GelMA+ gels was driven by a combination of diffusion and degradation of the material by MMP-9 enzymes. This work demonstrated that a GelMA+-based material that releases a therapeutic agent can be triggered by enzymes found in the tear fluid.

High specific activity [samarium-153] EDTA for imaging of experimental tumor models

Enriched samarium oxide (98.2% 152Sm2O3) was irradiated in low neutron flux and high neutron flux reactors to produce 153Sm with specific activities of 14.3 GBq and 22.1 TBq mmol-1 Sm, respectively, at the time of use. Formulation of 153Sm as [153Sm]EDTA, with a 1:10 molar ratio of SM:EDTA, provided a stable radiotracer in vitro and in vivo. High specific activity [153Sm]EDTA showed superior uptake in cell culture (20.8 +/- 0.9% vs. 5.5 +/- 0.1% for 6 and 600 pmol Sm per 10(6) cells, respectively) and better tumor index values (51 vs. 37 at 10.9 nmol and 1.09 mumol Sm kg-1, respectively) in the BDF1 mouse/Lewis lung tumor model. High specific activity [153Sm]EDTA scintigrams of Copenhagen x Fisher rats bearing transplanted Dunning R3327 tumors clearly delineated the tumors within 6 hr, with moderate liver and bone uptake and low soft-tissue background. The injected radiotracer underwent rapid central compartment clearance and whole-body elimination. The absence of observed adverse histopathological toxicity combines with high image quality within 6 hr, to support the clinical tumor-imaging potential of this agent. Comparative studies with [67Ga]citrate at molar-equivalent doses indicated that high specific activity [153Sm]EDTA was a superior radiotracer in these in vitro and in vivo models.

Comparative studies of radiotracer citrates in oncological models--2. 153Sm-citrate and 67Ga-citrate

153Sm-citrate solutions were prepared from enriched 152Sm2O3 which had been irradiated at 10(12)n cm-2 s-1 in the University of Alberta Slowpoke reactor. 153Sm was rapidly bound (93% in 2 h) by Melanoma 2AB cells in tissue culture upon incubation in the presence of 153Sm-citrate (1.9 nmol 10(6) cells). In vitro ultracentrifugation studies of 153Sm-citrate solutions showed that colloid formation under incubation conditions could have been responsible in part for the uptake by cultured cells. Low uptakes (less than 1% in 2h) of 67Ga-citrate were seen under similar conditions. 153Sm-citrate injected into BDF1 mice (Lewis lung carcinoma) and Copenhagen x Fisher rats (Dunning R3327-H prostatic tumors) was concentrated mainly in the liver, with some tumor and bone uptake. The percent of injected dose per organ for 153Sm and 67Ga in the murine and rat models respectively, 24 h after i.v. dosing, was 17.2 +/- 4.7 and 2.0 +/- 0.6 (tumor), 63.9 +/- 7.9 and 14.4 +/- 1.4 (liver) and 0.6 +/- 0.1 and 1.3 +/- 0.1 (blood); % injected dose g-1 femur was 6.2 +/- 2.7 and 12.9 +/- 2.7, respectively. Scintigrams of rats showed qualitative biodistributions similar to the quantitative mouse data obtained by dissection studies. The high hepatic uptake detracted from the otherwise superior tumor localization of 153Sm-citrate when compared to 67Ga-citrate in these models. The murine Lewis lung tumor index (% injected dose g-1 tumor x tumor: blood) was 303.6 for 153Sm-citrate and 48.9 for 67Ga-citrate, 24 h after injection.

Comparative studies of radiocitrates in oncological models--I. 99mTc citrate and 67Ga citrate uptake by EMT-6 tumors in mice

67Ga citrate and 99mTc citrate (Solcocitran) were injected sequentially, with an interval of 48 h, into Balb/c mice bearing transplanted EMT-6 tumors. Tissue distributions of 67Ga and 99mTc were measured simultaneously at intervals of 1, 3, 5 and 8 h after injection of the 99mTc citrate (49, 51, 53 and 56 h after 67Ga citrate). Maximal tumor:blood ratios for 67Ga and 99mTc were 13.8 +/- 3.2 and 4.0 +/- 1.0 respectively, both occurring at the final period. The maximum tumor index (T.I. = T:B X % dose/g) for 67Ga was 71 +/- 23% 56 h after injection, and for 99mTc was 13 +/- 12% 1 h after injection. Liver, kidney and spleen had equal or higher concentrations of radioactivity than tumor for either radiotracer. The somewhat higher tumor:blood ratio for 67Ga citrate was offset by the time required for this optimum to be reached. Alternatively, the best 99mTc citrate tumor:blood ratios were attained within 8 h, with less liver and gut radioactivity. These data fall within the range of results from other clinical and animal model studies of 67Ga citrate and 99mTc citrate. In view of the radiation dose, the inconvenience of the 48-72 h wait, and the cost of 67Ga, and because neither radiopharmaceutical is tumor specific, 99mTc citrate may have a place in early oncological screening. The results are discussed as part of a comprehensive review of the 99mTc citrate literature.

Hepatic reticuloendothelial function in the sub-totally nephrectomized rat model of chronic uremia

The chronic uremic condition was induced in male Wistar rats by long term maintenance of the animals following sequential sub-total and contralateral nephrectomies. Hepatic reticuloendothelial (RES) activity was estimated by non-invasive measurement of blood clearance rates and hepatic uptake of 99Tcm sulfur colloid administered intravenously. The blood half-time, and the blood clearance rate constants for normals and chronic uremics were 78 +/- 10 s and 49.5 +/- 5 s, and 7.51 +/- 1.04 x 10(-3) s-1 and 10.81 +/- 1.17 x 10(-3) s-1 respectively. The normal hepatic uptake rate constant was 9.03 +/- 1.25 x 10(-3) s-1, compared with a uremic uptake rate constant of 14.34 +/- 1.51 s-1. Measurement of total liver radioactivity upon termination, 15 min after injection, showed significantly increased total uptake in uremia, whereas no change in spleen radioactivity was observed. The clinical implications of these data are discussed.