Introduction
The appropriate method of drug delivery has a significant effect on the efficiency of the drug and its side effects. Novel drug delivery approaches seek to design effective drug delivery systems with goals such as reducing side effects, increasing bioavailability, and targeted transfer of drugs on the one hand, and overcoming barriers such as the blood-brain barrier, on the other hand [1]. The use of microparticles as drug carriers in different systems has improved the therapeutic performance of drugs due to having advantages such as the possibility of easier preparation, controlled drug release, and targeted drug delivery [2]. Microparticles are drug delivery systems designed for stable and controlled delivery of drugs for a long period of time. Microparticles have a small core consisted of solid or liquid materials that are surrounded by natural or synthetic polymer films or carriers, with different thickness and degree of permeability. These films or carriers act as the regulator of drug release rate. The coating of microparticles can be considered as a factor to mask their unpleasant taste and odor, and increase the stability and even the solubility of the active pharmaceutical ingredient [3, 4, 5]. Spray drying method is used for changing liquid contents into dry particles by spraying the liquid into a hot drying chamber through providing a sufficient volume of hot air which can evaporate the liquid droplets and dry the particles scattered in this environment. The content can be a solution, suspension, emulsion, gel or paste, provided that it can be pumped and sprayed [6].
Clotrimazole is a broad-spectrum antifungal drug that is mainly used to treat Candida albicans and other fungal infections. Clotrimazole, a synthetic imidazole antifungal, is widely used as a topical treatment for foot infections in athletes and also to treat vulvovaginal and oropharyngeal candidiasis [11]. Clotrimazole is a very lipophilic drug with a partition coefficient higher than 5 and a very low solubility in water (0.49 mg/L), which can reduce the bioavailability of the drug [13]. Therefore, techniques such as preparation of microparticles from the drug, depending on the type of used coating, can help increase the solubility or increase the release rate of the drug from the final pharmaceutical form. In this study, an attempt was made to make clotrimazole microparticles by using two types of hydrophilic (polyethylene glycol) and lipophilic (beeswax) coatings and the spray drying technique, and then assess the effect of coating type on physicochemical behaviors such as particle size and dissolution and release rate of the drug from the particles.
Methods
Fabrication of clotrimazole microparticles using beeswax and polyethylene glycol
To produce clotrimazole microparticles consisting of beeswax or polyethylene glycol (PEG 6000), a modified (in-house) method was used adapted from the method proposed by Fouad et al [14]. It was used at a temperature of 70°C. The dried particles containing carrier and drug were separated from the walls of the chamber and subjected to further analysis (Table 1).


Physicochemical evaluation of clotrimazole microparticles
Obtained microparticles were subjected to particle size analysis using optical microscopy and Zetasizer technique. Particle morphology evaluation was carried out using scanning electron microscope (SEM), and investigation of probable interactions between the drug and excipients in the microparticles was done using Fourier Transform Infrared Spectroscopy (FTIR). Drug release rate from microparticles was also tested. 
Results
The light microscope images with 1000x magnification showed that the particles were mostly spherical with irregular surfaces. The formulations F1 to F3 (microparticles coated with different proportions of beeswax) had a diameter of about 20 micrometers. On the other hand, formulations F4 to F6 (microparticles coated with different proportions of polyethylene glycol) had a diameter of about 100 micrometers (Figure 1).

The resulting SEM images showed that the microparticles obtained from both methods had irregular surfaces and non-uniform morphology (Figure 2).

Regarding the Zetasizer results, the size of beeswax particles ranged 10-100 micrometers, while the size of polyethylene glycol particles ranged 100-1000 micrometers (Figure 3).

The FTIR results showed that the specifications of infrared absorption peaks of pure Clotrimazole related to C-H aromatic branch (13176 cm-1), C=C aromatic branch (1589 cm-1), C=N branch (11570 cm-1) and C-H aromatic band (1761 cm-1) was repeated in the FTIR spectrum obtained from microparticles with polyethylene glycol, but these peaks were not observed in the microparticles fabricated by beeswax (Figure 4).

After drawing the calibration curve for clotrimazole in phosphate buffer pH=7.4, the drug release rate of all six formulations were evaluated at time intervals of 30, 60, 180 and 360 minutes and a wavelength of 260 nm. The results showed that the cumulative release rate of clotrimazole in formulations F1 to F3 increased from 41 to 80%, respectively. This pattern was the same in formulations F4 to F6 where the cumulative release rate increased from 46 to 79% (Figure 5 and Table 1).

Discussion
In this study, clotrimazole drug was tuned into microparticles using spray drying method and used on two carriers of beeswax and polyethylene glycol 6000 in different ratios. The results of particle analysis using Zetasizer technique showed that the size of microparticles prepared from beeswax and polyethylene glycol 6000 were below 1000 micrometers in all ratios. The size of microparticles prepared from beeswax with three ratios were in the range of 10-100 micrometers. Examining the three ratios of microparticles prepared from polyethylene glycol 6000 showed that, compared to beeswax, the size of particles was in the range of 100-1000 micrometers, and this range showed a significant difference compared to that of microparticles from beeswax. A similar study in 2012 used polyethylene glycol 6000, mannitol, carbopol 934, stearic acid, and beeswax to prepare solid lipid nanoparticles containing clotrimazole, and it was shown that the size of particles was in the range of 100-1000 nanometers [17]. It is consistent with the results related to the size of microparticles prepared with polyethylene glycol 6000 in our study. In another study that was conducted for the local use of clotrimazole microparticles, it was shown that the size of clotrimazole particles (prepared with stearic acid as solid lipid, and oleic acid as liquid lipid) were in the range of 100-200 nm [16].
The drug release pattern showed that the highest rate of release over time was seen in formulations F3 and F6 (80.52% and 79.29%, respectively). There was no statistically significant difference in the drug release rate in 6 hours between these two formulations (P>0.05). It seems that due to the very high lipophilicity of Clotrimazole, the most important step in determining the drug release rate is the dissolution of the drug in an aqueous medium, in addition to the role of lipophilic or hydrophilic carrier. Therefore, the drug release rate over time between microparticles prepared from beeswax and polyethylene glycol was not significantly different. This justifies the reason for increased drug release rate in formulations that contain a lower portion of the drug. Over time, a certain amount of the drug is dissolved in an aqueous medium; in formulations F1 and F4, since the amount of drug was more than that in formulations F3 and F6, a lower portion was dissolved. These results have been observed in other studies on clotrimazole [18]. However, some studies have confirmed the increase of clotrimazole solubility by using solid dispersion technique and compounds such as sugars (mannitol) or water-soluble polymers (Pluronic) [19, 20].
Overall, it can be concluded that both lipophilic and hydrophilic coatings of clotrimazole show a similar pattern of drug release; however, regarding the reaction of the polymer with the drug, clotrimazole microparticles coated by beeswax have interactions with drug, which means that coating by polyethylene glycol 6000 polymer has superiority.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the ethics committee of Guilan University of Medical Sciences (Code: IR.GUMS.REC.1396.492). All ethical principles were observed in this study. 

Funding
This research was done with the financial support of Kobra Najafzadeh Mahvizani.

Authors' contributions
Study concept and design: Zahra Hesari; Acquisition, analysis, or interpretation of data: Kobra Najafzadeh-Mahvizani, Gita Alkan Saberi; Drafting of the manuscript: Zahra Hesari; Statistical analysis: Zahra Hesari, Kobra Najafzadeh-Mahvizani; Funding acquisition: Kobra Najafzadeh-Mahvizani, Zahra Hesari; Administrative, technical, or material support: Marjan Daei hamed, Zahra Hesari; Study supervision: Zahra Hesari.

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
The authors would like to thank the School of Pharmacy, Guilan University of Medical Sciences and the Journal of Gilan University of Medical Sciences for their cooperation.

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