Visualizing fluid transport inside orally disintegrating tablets and changes in tablets using real-time X-ray radiography and X-ray computed tomography.

OBJECTIVE: To investigate the disintegration of wet- and dry-compressed orally disintegrating (OD) tablets, with synchrotron radiation as the X-ray source. SIGNIFICANCE: Pharmaceutical tablets are vital for the treatment of various diseases. Therefore, they are constantly developed to ensure desirable characteristics. In particular, OD tablets need to disintegrate immediately after absorbing saliva. How these tablets absorb saliva is key to enhancing rapid product development. Recently, absorption processes have been investigated using various noninvasive techniques, including X-ray radiography and X-ray computed tomography. However, X-ray radiography studies on how water without a contrast agent is absorbed, moves, and causes a tablet to swell are scarce. The use of a contrast agent is associated with some shortcomings, including complex data analysis in some instances, alterations in the viscosity of water, and potential influence on fluid transport inside the tablet, thus possibly affecting the disintegration process. METHODS: Real-time X-ray radiography was used to monitor the disintegration of various tablets, while X-ray computed tomography and software were used to create 3 D images. RESULTS: We demonstrated how pure water penetrated the wet-compressed tablet faster than inside the dry-compressed tablet, and how the latter swelled more. X-ray computed tomography showed the presence of voids in the tablets following water absorption. CONCLUSION: Our methods are promising for nondestructive fluid absorption and transport investigations inside OD tablets.

Engineering the expression system for Komagataella phaffii (Pichia pastoris): an attempt to develop a methanol-free expression system.

The construction of a methanol-free expression system of Komagataella phaffii (Pichia pastoris) was attempted by engineering a strong methanol-inducible DAS1 promoter using Citrobacter braakii phytase production as a model case. Constitutive expression of KpTRM1, formerly PRM1-a positive transcription regulator for methanol-utilization (MUT) genes of K. phaffii,was demonstrated to produce phytase without addition of methanol, especially when a DAS1 promoter was used but not an AOX1 promoter. Another positive regulator, Mxr1p, did not have the same effect on the DAS1 promoter, while it was more effective than KpTrmp1 on the AOX1 promoter. Removing a potential upstream repression sequence (URS) and multiplying UAS1DAS1 in the DAS1 promoter significantly enhanced the yield of C. braakii phytase with methanol-feeding, which surpassed the native AOX1 promoter by 80%. However, multiplying UAS1DAS1 did not affect the yield of methanol-free expression by constitutive KpTrm1p. Another important region to enhance the effect of KpTrm1p under a methanol-free condition was identified in the DAS1 promoter, and was termed ESPDAS1. Nevertheless, methanol-free phytase production using an engineered DAS1 promoter outperformed phytase production with the GAP promoter by 25%. Difference in regulation by known transcription factors on the AOX1 promoter and the DAS1 promoter was also illustrated.