Drug nanocrystals for the treatment of inflammatory bowel diseases (IBD)

Abstract

Inflammatory bowel disease (IBD) is a group of chronic inflammatory diseases of the gastrointestinal tract that mainly includes Crohn's disease (CD) and ulcerative colitis (UC). The progressive understanding of the pathophysiological mechanisms of IBD led to the development of more drugs for IBD e.g., anticoagulants and hemin. However, this search should be accompanied by extensive research into systems that can safely deliver these new drugs to their targets while sparing their off-target distribution. Therefore, drug nanocrystals (NCs), which contain the highest amount of drug per particle and can passively accumulate in inflamed tissues, were selected. <br /> Therefore, fluorescent nano- and microcrystals (MCs), RX nano- and microcrystals, and RX nanocrystals with different surface charges were prepared by wet milling to evaluate their selectivity for inflamed tissue. The evaluation of the formulation factors showed that the most important factors were the concentration of the stabilizer solution, the diameter of the beads, and the milling time. In vitro evaluation of the anti-inflammatory activity of rivaroxaban NCs, MCs, and solution revealed that the anionic nano- and microcrystals were the only formulations that caused a reduction in percent inhibition of secreted embryonic alkaline phosphatase (SEAP) amount in the culture media in J774-DUAL^TM macrophage cells with a comparable value of approximately 54%. The difference in bioadhesion to inflamed tissue between MCs and NCs was found to be 13- and 15-fold higher than in noninflamed tissue, respectively. Moreover, the anionic NCs and RX microcrystals were tested in the TNBs colitis model, where they showed comparable anti-inflammatory effects in terms of their ability to reduce the parameters measured. However, the application of RX NCs with different surface charges revealed that anionic NCs had a stronger anti-inflammatory effect than nonionic and cationic NCs, as evidenced by their ability to decrease MPO (79.1± 11.9 U/g tissue) and TNF-α levels (497.1± 158.3 U/g tissue) in colonic tissue compared with the colitis control group (608.2± 241.5 and 1583± 492.1 U/g tissue, respectively). Furthermore, the assessment of factor Xa levels in blood showed that RX anionic NCs produced levels lower than the levels produced with MCs, and solution, suggesting a systemic anticoagulation effect. <br /> Hemin was selected for the second study because hemin NCs are needle-shaped allowing the study of the effect of the shape of NCs. The NCs showed lower toxicity and higher anti-inflammatory effects than the solution in vitro and in the TNBS colitis model, hemin NCs at a dose of 10 mg/Kg had the best anti-inflammatory effect, as evidenced by their ability to reduce MPO levels (162.8± 65.6 U/g tissue) and TNF-α levels (606. 4± 320.5 U/g tissue) and IL-1β levels (657.7± 109.1 U/g tissue) compared with the colitis control group (608.2± 241.5, 1583± 492.1, and 1790± 386.3 U/g tissue, respectively). The presence of hemin NCs as needles suggests that the needle form of these NCs did not hinder but might rather enhance the effect of hemin in the treatment of IBD. From the previously described studies, it was concluded that the formulation of drugs as NCs enhances their anti-inflammatory effect for IBD management. Their ease of preparation and the ability to deliver a higher amount of drug compared to polymeric or lipid-based NPs exploit the great potential of using drug nanocrystal technology in IBD. Further studies are required to determine the effect of oral NCs or their gastroprotective-coated equivalents in improving drug efficacy for the treatment of IBD.