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Up until this point our discussion has centered around the beautification of the human nail by way of UV nail gel. An alternative technique has been developed that would allow the UV nail gel to be the carrier for transporting drugs that are needed to treat certain toenail diseases such as onychomycosis.

Researchers [26] in this case utilized the Curanail coating (32 wt.% Amorolfine HCl UV-cured coating), 3 wt.%. Amorolfine HCl UV-cured coating, and 4 wt.%. Terbinafine HCL UV-cured coating as shown in Table 3.10. The study was carried out using human nail secured from patients ages 18 to 65 years. The permeation study was carried out and the results are shown in Table 3.10 whereby all anti-onychomycotic drugs penetrated the nail plate delivering the agent to terminate the fungus. The major benefit here is the long residence time that the anti-onychomycotic drug is able to stay on the nail plate delivering it over a long period of time. It is obvious that other traditional topical therapy would not last as long due to the environment that the nail plate resides in [26].

Table 3.9 Photopolymerizable cellulose esters that act as the ‘Achilles heel’ in the UV cure nail gel polymer allowing easy removal of the coating by acetone soak yet maintaining MEK double rub performance. The acetone solubility test is carried out by immersing a dry, pre-weighed sample of the coating in acetone for 48 hours at 25°C. The coating is removed, dried for 16 hours at 60°C in a forced-air oven, and reweighed. The weight percent of the insoluble coating remaining is calculated from the data.

Cellulose Ester Type	Pencil Hardness	Acetone Insolubles Wt.% Film Recovery	MEK Double Rubs
CA 320S (Control)1	F	0	<10
CAP 504 (Control)1	HB	0	<10
CAB 553 (Control)1	2B	0	<10
Nitrocellulose (RS ½ sec.)1	3B	0	<10
CA Maleate (0.32 DS)	H/2H	94	>200
Sample 1
CAP Maleate (0.10 DS)	F	42	98
Sample 2
CAP Maleate (0.25 DS)	H	90	>200
Sample 3
CAP Maleate (0.39 DS)	H/2H	94	>200
Sample 4
CAP Maleate (0.46 DS)	H	91	>200
Sample
CAB Maleate (0.41 DS)	H/F	92	>200
Sample 6
CAP Methacrylate (0.52 DS)	H/F	31	91
Sample 7
CAP Acrylate (0.25 DS)	F	43	62
Sample 8
CAB Methacrylate (0.40 DS)	F	48	109
Sample 9
CAB Acrylate (0.20 DS)	F	29	41
Sample 10
CAP TMI (0.59 DS)	2H	82	>200
Methacrylate (0.30 DS)
Sample 11
CAB TMI (0.62 DS)	H	88	>200
Methacrylate (0.2 DS)
Sample 12

Sample 8 (CAP Acrylate (0.25) might be a good candidate for GAL-FL or LED. (Control)¹: Not formulated, (DS): degree of substitution per glucose ring.

Table 3.10 Lag time (the time that the coating was on the nail), steady-state flux, permeability coefficient, diffusion coefficient and amount of drug in nail clippings.

Formulation	Lag time (day)	Steady-state flux (μg/cm2/day)	Permeability coefficient × 10-5 (cm/day)	Diffusion coefficient × 10-5 (cm2/day)	Drug in nail clipping (μg/cm2)
Curanail film (32 wt.% Amorolfine HCl)	10.4 ± 1.3	2.9 ± 0. 2	5.8 ± 0.3	2.5 ± 0.5	61.1 ± 14.8
3 wt.% Amorolfine HCl UV-cured film	10.4 ± 0.9	2.4 ± 0.2	7.9 ± 0.7	2.7 ± 0.8	37.5 ± 17.6
4 wt.% Terbinafine HCl UV-cured film	9.5 ± 1.2	1.5 ± 0.1	3.7 ± 0.3	1.6 ± 0.4	71.1 ± 8.0
Statistical difference between Curanail and Amorolfine UV-cured film?	No (p>0.05)	Yes (p<0.05)	Yes (p<0.05)	No (p>0.05)	Yes (p<0.05)
Statistical difference between Amorolfine and Terbinafine UV-cured film?	No (p>0.05)	Yes (p<0.05)	Yes (p<0.05)	Yes (p<0.05)	Yes (p<0.05)

Figure 3.19 UV nail gel construction: Human nail, UV nail gel base coat which is used primarily to obtain adhesion to the human nail and to even out irregularities of the surface, UV nail gel color coat or clear coat that can result in multiple shades or clear to show the natural color of the nail, and UV nail gel top coat that ultimately results in the performance layer of the nail.