# Therapeutic Hydrogel Lenses and the Antibacterial and Antibiotic Drugs Release
## 3 Results
### Time Course and Drug Interaction with the Lenses  
The time courses of the interactions between the tested drugs and the lenses are reported in Figure 2. Evaluations were performed at time points of 0.5, 1, 2 and 24 h. These time point were selected because longer times did not reflect eyedrop persistence due to the ocular clearance. The amounts of drugs eluted through the lenses at each time course were determined by gradient HPLC as applied to the fluid eluted through the lenses contained in the lower parts of the wells.  
Figure 1: HPLC gradient analysis of drugs examined for their interaction with hydrogel lenses. \(X\) axis: elution time through the chromatographic column. \(Y\) axis: absorbance intensity at the specific wavelength used for each drug (dexamethasone, 239 nm; chloramphenicol and betamethasone, 241 nm; bromophenacyl bromide, 280 nm). Panel (A): peak 1 dexamethasone; peak 2 background signal. Panel (B): peak 1 chloramphenicol, peak 2 betamethasone. Panel (C): peak 2 bromophenac, peaks 1 and 3 background signals. The identity of each peak was confirmed by mass spectrometry analysis (see Materials and Methods). Background signals are due to contaminants disagreeing with the theoretical molecular weight of the drugs analyzed.  
Figure 2: Average passage of tested drugs through the lenses at all time points tested. \({}^{**}p<0.01\) G-72 HW vs. C75%. \({}^{\circ}p<0.05\) G-72 HW vs. Balafilcon A. \(\lx@sectionsign p<0.05\) Balafilcon Avs C75%.  
At 0.5, 2, and 24 h, the lens allowing the most abundant passage of betamethasone was the G72 HW lens, by the Balafilcon A and C75 lenses. Only at 1 h was the Balafilcon A lens slightly more effective than the G72 HW lens in allowing drug passage. These differences were significant for the G72 HW lens compared to the other lenses at 2 and 24 h.  
The lens allowing the most abundant passage of bromophenacyl bromide at 0.5 h was the C75 lens (\(p=0.05\)), while at 1 h, the G72 HW lens ranked highest. No significant differences were detected at other time points or between other lenses.  
The lens allowing the most abundant passage of dexamethasone was the G72 HW lens, but only at 0.5 h and 1 h.  
Regarding chloramphenicol, the G72 HW and Balafilcon A lenses allowed more abundant passage than the C75 lens at all time points tested, except for 2 h, when no significant difference between the Balafilcon A and C75 lenses was observed.  
The drug that passed most readily through all lenses was chloramphenicol. Conversely, for anti-inflammatory drugs, differences were observed only at the latest (2 and 24 h for betamethasone) or earliest (0.5 and 1 h for dexamethasone and bromophenacyl bromide) time points.  
The average quantities of drugs that passed through the lenses at all tested time points are reported in Figure 3. Significant differences were observed for the following: (a) the G72 HW and Balafilcon A lenses compared to the C75 lens for betamethasone and chloramphenicol; (b) the G72 HW lens compared to the Balafilcon A lens for all tested drugs. For the ionic lens, the regression line equation displays a positive angular coefficient with a high R2 value, thus indicating a continuous drug release from the lens increasing from 30 min to 24 h. For the non-ionic lens, the regression line equation displays a negative angular coefficient with a high R2 value, thus indicating a decrease in drugs release from the lens from 30 min 2 to 24 h.