Fig. 1.
Schematic of the hydrogel implant designed for veterinary glaucoma surgical use
Table 1.
Food-grade gelatine solutions and formulations
| Concentration (%) | Gelatine mass (g) | Distilled water volume (mL) |
|---|---|---|
| 5 | 0.526 | 10 |
| 10 | 1.120 | 10 |
| 15 | 1.765 | 10 |
Table 2.
Small-increment formulation changes to hydrogel samples
| Gelatine type | Concentration (%) | Sample No. | Glutaraldehyde addition (mL) | Storage environment |
|---|---|---|---|---|
| 15 | 1 | 19 | ||
| Chemically purified | 15 | 2 | 21 | Ethanol 99.8% |
| 16 | 3 | 20 | ||
| 15 | 4 | 20 |
Fig. 2.
Schematic diagram of the setup for measuring the ionic conductivity of hydrogels
Table 3.
Comparison of the quality of food-grade gelatine hydrogels by gelatine concentration
| Concentration (%) | Dissolution temperature (°C) | Crosslinking | Hydrogel shape |
|---|---|---|---|
| 5 | 55.0 | Partial | No shape |
| 10 | 55.2 | Complete | Impermanent shape |
| 15 | 58.0 | Complete | Preserved shape |
Table 4.
Comparison of the properties of food-grade and chemically purified gelatine hydrogels
| Gelatine type | Concentration (%) | Dissolution temperature (°C) | Crosslinking speed |
|---|---|---|---|
| Food-grade | 15 | 58.0 | Average |
| Chemically purified | 15 | 43.2 | High |
Table 5.
Comparison of the properties of food-grade and chemically purified gelatine hydrogels after 72 h immersion
| Gelatine type | Concentration (%) | Immersion environment | Shape retention |
|---|---|---|---|
| Chemically purified | 15 | Ethanol | Preserved shape, durable, stiff and stable |
| Chemically purified | 15 | Water | Preserved shape, numerous cracks on the surface |
| Food-grade | 15 | Water | Partial disintegration |
Fig. 3.
Effect of immersion environment on the compressive strength of all types of hydrogel samples. A – sample No. 1 with a glutaraldehyde concentration of 15% and the addition of 19 mL of glutaraldehyde; B – sample No. 2 with a glutaraldehyde concentration of 15% and the addition of 21 mL of glutaraldehyde; C – sample No. 3 with a glutaraldehyde concentration of 16% and the addition of 20 mL of glutaraldehyde; D – sample No. 4 with a concentration of 15% and the addition of 20 mL of glutaraldehyde. Blue line – sample immersed in ethanol; orange line – sample immersed in water
Fig. 4.
Comparison of compressive strength for different hydrogel formulations immersed in 99.8% ethanol. Type 1 – hydrogel of 15% gelatine concentration and 19 mL glutaraldehyde; Type 2 – hydrogel of 15% gelatine concentration and 21 mL glutaraldehyde; Type 3 – hydrogel of 16% gelatine concentration and 19 mL glutaraldehyde; Type 4 – hydrogel of 15% gelatine concentration and 20 mL glutaraldehyde
Table 6.
Results of the compression test of hydrogels immersed in alcohol
| Relative shortening under given force (mm) | |||||
|---|---|---|---|---|---|
| Sample No. | 10 N | 20 N | 30 N | 40 N | 50 N |
| 1 | 3.04 | 3.65 | 4.06 | 4.26 | 4.55 |
| 2 | 5.24 | - | - | - | - |
| 3 | 4.67 | 5.82 | - | - | - |
| 4 | 3.24 | 4.13 | 4.55 | 4.97 | 5.23 |
Fig. 5.
Comparison of KCl ion concentrations in the test tubes (where the solution before passing through the hydrogel is the ion source in the system) for the tested samples. No. 1 – hydrogel of 15% gelatine concentration and 19 mL glutaraldehyde; No. 2 – hydrogel of 15% gelatine concentration and 21 mL glutaraldehyde; No. 3 – hydrogel of 16% gelatine concentration and 19 mL glutaraldehyde; No. 4 – hydrogel of 15% gelatine concentration and 20 mL glutaraldehyde
Fig. 6.
Comparison of KCl ion concentrations in the containers (after passing through the hydrogel) for the tested samples. No. 1 – hydrogel of 15% gelatine concentration and 19 mL glutaraldehyde; No. 2 – hydrogel of 15% gelatine concentration and 21 mL glutaraldehyde; No. 3 – hydrogel of 16% gelatine concentration and 19 mL glutaraldehyde; No. 4 – hydrogel of 15% gelatine concentration and 20 mL glutaraldehyde
Fig. 7.
Differential scanning calorimetry curve of a hydrogel sample immersed in water but not alcohol cured, with a marked transformation region
Fig. 8.
Differential scanning calorimetry curve of a hydrogel sample cured in 99.8% ethanol, with a marked transformation region
Fig. 9.
Microstructure of hydrogels at 100× magnification. A – alcohol-conditioned hydrogel; B – water-conditioned hydrogel
Fig. 10.
3D analysis proceeding from 100× magnification of pore distribution in hydrogel samples. A – alcohol-conditioned hydrogel; B – water-conditioned hydrogel
Fig. 11.
Microstructure of hydrogel samples at 200× magnification. A – alcohol-conditioned hydrogel; B – water-conditioned hydrogel
Fig. 12.
Comparison of microstructure of samples at 20× magnification A – alcohol-conditioned hydrogel; B – water-conditioned hydrogel
Table 7.
Mechanical properties of the developed implant alongside those of available clinical solutions
| Designed implant | XEN Gel Stent | EX-PRESS | Baerveldt | |
|---|---|---|---|---|
| Material | Gelatine + glutaraldehyde | Pork gelatine + glutaraldehyde | Stainless steel | Silicone |
| Inner dia | 1–3 mm (core) | 45 μm | 50 μm | 300 μm |
| Length | As needed | 6 mm | 2.64 mm | Various |
| Flexibility | High after hydration | 10° (15 μN), 35° (70 μN) | Rigid | 2,000 μN |