## 1 Introduction  
Chronic obstructive pulmonary disease (COPD) is a life-threatening chronic respiratory disease and the fourth most common cause of death within the last decade [1]. According to the Global Initiative for Chronic Obstructive Lung Disease (GOLD), COPD is defined as \"a common, preventable, and treatable disease that is characterized by persistent respiratory symptoms and airflow limitation that is due to airway and/or alveolar abnormalities usually caused by significant exposure to noxious particles or gases\" [2]. The disease triggers pathological processes such as hypoxia, electrolyte disturbances, and changes in pulmonary hemodynamics and is often accompanied by extra-pulmonary manifestations such as thromboembolic and hemorrhagic events [1]. According to American Lung Association, smoking is the leading cause of COPD while a genetic condition called alpha-1 deficiency, exposure to air pollution, breathing secondhand smoke, and working with chemicals, dust, and fumes are the main risk factors for COPD.  
Pharmacologic management of COPD aims for the reduction of the current symptoms and future exacerbation risks [3]. Treatment of the disease is conducted with inhaled bronchodilators, corticosteroids [4], or long-acting beta-agonists. If the patients have severe symptoms or intense exacerbations, combination therapy has been recommended because it lowers the incidence of exacerbations [3, 5]. Budesonide (BUD) belongs to a class of drugs known as corticosteroids. It works directly in the lungs, making breathing easier by reducing the irritation and swelling of the airways [6]. BUD is a highly hydrophobic compound with poor absorption and minimal oral bioavailability in humans and animals [7]. Consequently, the inclusion of BUD in polymeric nanoparticles aiming in the amelioration of its bioavailability has been examined extensively by many research groups. Our group prepared BUD-loaded chitosan nanoparticles [8], [PERSON] et al. prepared chitosan-coated PLGA nanoparticles [9], while [PERSON] et al. prepared BUD-loaded polydopamine nanoparticles [10], and [PERSON] et al. prepared spray-dried BUD-loaded microparticles composed of dipalmitoylphosphatidylcholine, chitosan, lactose, and L-leucine.  
Cyclodext (CDs) are cyclic oligosaccharides consisting of glucopyranosyl units linked with \(\alpha\)-(1,4) bonds [11]. The natural CDs \(\alpha\)-, \(\beta\)-, and \(\gamma\)-CDs are composed of 6, 7, and 8 glucose units, respectively [12]. CDs have a unique torus structure composed of an inner hydrophobic cavity and a hydrophilic external surface with primary and secondary hydroxyl groups. Attributed to their structure, CDs are able to host lipophilic, non-polar molecules in their inner cavity by forming inclusion complexes [13; 14]. The thermodynamic equilibrium between the different components of the system (CD, guest molecule, solvent) [15] affects drastically the successful formation of inclusion complexes. The formulated inclusion complexes are stable in aqueous environments owed to CD's hydrophilic external surface, and consequently, CDs are widely used in pharmaceuticals, drug delivery systems, cosmetics, and the food and chemical industries [12].  
In this study, CD inclusion complexes were prepared through the solvent evaporation technique and BUD was entrapped in their interior (Figure 1). The effect of the solvent's different ratio during the formation of the inclusion complexes was examined for the first time. Moreover, different percentages of BUD were entrapped through the optimum conditions, and the resulted inclusion complexes were characterized. The main purpose was the preparation of an effective carrier for BUD, aiming in the amelioration of its in vitro release behavior and consequently its bioavailability.