Terahertz Time of Flight Spectroscopy as a Coating Thickness Reference Method for Partial Least Squares Near Infrared Spectroscopy Models.

Near infrared spectroscopy (NIRS) is often used during the tablet coating process to assess coating thickness. As the coating process proceeds, the increase and decrease in NIRS signal from both the coating formulation and tablet core has been related to coating thickness. Partial least-squares models are often generated relating NIRS spectra to reference coating thickness measurements for in-line and/or at-line monitoring of the coating process. This study investigated the effect of the reference coating thickness measurements on the accuracy of the model. The two primary reference techniques used were weight gain-based coating thickness and terahertz-based coating thickness. Most NIRS coating thickness models currently use weight gain-based reference values; however, terahertz-time-of-flight spectroscopy (THz-TOF) offers a more direct reference coating thickness measurement. Results showed that the accuracy of the NIRS coating thickness model significantly improved when terahertz-based coating thickness measurements were used as reference when compared to weight gain-based coating thickness measurements. Therefore, the application of THz-TOF as a reference method is further demonstrated.

Determining the effect of photodegradation on film coated nifedipine tablets with terahertz based coating thickness measurements.

Film coating of nifedipine tablets is commonly performed to reduce photo-degradation. The coating thickness of these tablets is a primary dictating factor of photo-stability. Terahertz spectroscopy enables accurate measurement of coating thickness. This study identifies a method to determine an end-point of a photo-protective coating process by using coating thickness measurements from terahertz time of flight spectroscopy (THz-TOF). For this method, nifedipine tablets, at different coating thicknesses, were placed in a photostability chamber. The illumination conditions of the coated tablets were adjusted based on the time duration of these tablets inside the chamber. A multiple linear regression model was developed with the coating thickness estimates from THz-TOF and illumination conditions information to predict the amount of drug remaining after photo-degradation (percent label claim). The prediction error of this model was 1.03% label claim in the range of 88.4-100.6% label claim. According to this model, acceptable levels of photo-protection in illumination conditions of up to approximately 700,000 lx hours was achieved at the end of the coating process (approximately 50 µm coating thickness) performed in this study. These results suggest THz-TOF as a viable process analytical technology tool for process understanding and end-point determination of a photo-protective coating process.

Electroporation as an efficient method of gene transfer.

Gene transfer by electroporation is an indispensable method for the study of developmental biology, especially for the study using chick embryos. Here we briefly review the principles of the method, and its application to chick embryos. Methods of transient misexpression and long-term misexpression by retrovirus vector or transposon system, and knockdown by small interference RNA are reviewed.

Cloning and developmental expression of a chick G-protein-coupled receptor SCGPR1.

To identify spinal motor neuron subtype-specific transcripts, we employed a single cell subtractive screen of mRNAs in chick embryos. We cloned a differentially expressed gene that termed spinal cord G-protein-coupled receptor 1 (SCGPR1) from its expression pattern that change dynamically in the developing spinal cord. The vertebrate orthologue of SCGPR1 is termed Gpr37 (GPCR/CNS1, ET(B)R-LP-1, Pael-R), however the specific ligand of this receptor has not been identified. Recent studies indicate that Pael-R can associate with parkin, a ubiquitin ligase which accumulates in Lewy bodies in dopaminergic neurons and is associated with Parkinson's disease. Although SCGPR1 (Gpr37) expression has been examined in adult tissues, the embryonic expression has not reported. Here, we have defined the expression pattern of SCGPR1 by in situ hybridization during chick development. SCGPR1 was first detected at HH stage 7 in the neural tube and notochord. As development progressed, SCGPR1 expression became restricted to the ventral neural tube. SCGPR1 expression was also present in the developing telencephalon, mesencephalon, retina, visceral-class motor neurons, myotome and thyroid invagination.