Clotrimazole-Loaded Borneol-Based In Situ Forming Gel as Oral Sprays for Oropharyngeal Candidiasis Therapy

Abstract

Oral candidiasis encompasses fungal infections of the tongue and other oral mucosal sites with fungal overgrowth and its invasion of superficial oral tissues. Borneol was assessed in this research as the matrix-forming agent of clotrimazole-loaded in situ forming gel (ISG) comprising clove oil as the co-active agent and N-methyl pyrrolidone (NMP) as a solvent. Their physicochemical properties, including pH, density, viscosity, surface tension, contact angle, water tolerance, gel formation, and drug release/permeation, were determined. Their antimicrobial activities were tested using agar cup diffusion. The pH values of clotrimazole-loaded borneol-based ISGs were in the range of 5.59-6.61, which are close to the pH of 6.8 of saliva. Increasing the borneol content in the formulation slightly decreased the density, surface tension, water tolerance, and spray angle but increased the viscosity and gel formation. The borneol matrix formation from NMP removal promoted a significantly (p < 0.05) higher contact angle of the borneol-loaded ISGs on agarose gel and porcine buccal mucosa than those of all borneol-free solutions. Clotrimazole-loaded ISG containing 40% borneol demonstrated appropriate physicochemical properties and rapid gel formation at microscopic and macroscopic levels. In addition, it prolonged drug release with a maximum flux of 370 µg·cm^-2 at 2 days. The borneol matrix generated from this ISG obsentively controlled the drug penetration through the porcine buccal membrane. Most clotrimazole amounts still remained in formulation at the donor part and then the buccal membrane and receiving medium, repectively. Therefore, the borneol matrix extended the drug release and penetration through the buccal membrane efficiently. Some accumulated clotrimazole in tissue should exhibit its potential antifugal activity against microbes invading the host tissue. The other predominant drug release into the saliva of the oral cavity should influence the pathogen of oropharyngeal candidiasis. Clotrimazole-loaded ISG demonstrated efficacious inhibition of growth against S. aureus, E. coli, C. albicans, C. krusei, C. Lusitaniae, and C. tropicalis. Consequently, the clotrimazole-loaded ISG exhibited great potential as a drug delivery system for oropharyngeal candidiasis treatment by localized spraying.

Keywords: borneol; clotrimazole; gel; in situ forming; oropharyngeal candidiasis; solvent removal.

Figure 1

Chemical structures of clotrimazole (A), NMP (B), and borneol (C).

Figure 2

Rheological behavior of clotrimazole-loaded borneol-based ISG and related formulations, plotting between shear stress against shear rate (A) and relationship between viscosity and shear rate at room temperature (B).

Figure 3

Wettability of clotrimazole-loaded borneol-based ISG and related formulations on the surface of the glass slide, agarose gel, and buccal porcine. Results are shown as mean values ± SD and demonstrated at room temperature (n = 3). * and # represent a significant difference (p < 0.05) compared with ZCN.

Figure 4

Interfacial tension and gel-formation behavior of clotrimazole-loaded borneol-based ISGs and borneol solution in PBS with pH 6.8.

Figure 5

(A) Change of gel formation with time after contact with PBS with pH 6.8. (B) Morphological change of clotrimazole-loaded borneol-based ISG and related formulations after exposure with agarose gel containing PBS with pH 6.8.

Figure 6

Percentage of water inducing a phase separation of clotrimazole-loaded borneol-based ISGs and borneol solution. Results are shown as mean values ± SD, (n = 3). * represents a significant difference (p < 0.05) compared with 50BZCN.

Figure 7

Clotrimazole release through (A) nylon membrane and (B) permeability through porcine buccal membrane from 40BZCN compared with ZN (n = 6).

Figure 8

Photographs of the inhibition zone of ISG formulations containing 20–50% borneol (20BZCN-50BZCN) against S. aureus (A), E. coli (B), and C. albicans (C,D) (n = 3).