Evaluation of coating properties of enteric-coated tablets using terahertz pulsed imaging.

PURPOSE: Enteric coatings are used to reduce gastrointestinal side effects and control the release properties of oral medications. Although widely used, the effect of formulation and process conditions on physicochemical and functional properties of enteric coatings remains unclear. METHODS: Terahertz pulsed imaging (TPI) was employed to evaluate the coat properties of enteric coated tablets (ECTs) with various acid resistance. Other analytic methods, such as loss on drying, scanning electron microscopy and X-ray computed tomography were then used to validate the relationships established among 4 TPI-derived parameters and the physicochemical properties of enteric coatings. RESULTS: Weight gain measurement did not provide any information to assess acid resistance of enteric coating, whereas four TPI-derived parameters non-destructively reflected the coating properties such as thickness, coat uniformity, density, and water distribution, allowing the identification of the causes of poor acid resistance in certain ECT batches using a single measurement. These parameters also revealed the effect of coating conditions; in particular, coating under dry conditions led to less dense and nonuniform coatings with poor acid resistance. CONCLUSION: We demonstrated the utility of TPI to identify structural defects within ECTs with poor acid resistance. TPI-derived parameters can aid in formulation development and quality control of ECTs.

Quantitative analysis of visible surface defect risk in tablets during film coating using terahertz pulsed imaging.

Tablets are the most common form of solid oral dosage produced by pharmaceutical industries. There are several challenges to successful and consistent tablet manufacturing. One well-known quality issue is visible surface defects, which generally occur due to insufficient physical strength, causing breakage or abrasion during processing, packaging, or shipping. Techniques that allow quantitative evaluation of surface strength and the risk of surface defect would greatly aid in quality control. Here terahertz pulsed imaging (TPI) was employed to evaluate the surface properties of core tablets with visible surface defects of varying severity after film coating. Other analytical methods, such as tensile strength measurements, friability testing, and scanning electron microscopy (SEM), were used to validate TPI results. Tensile strength and friability provided no information on visible surface defect risk, whereas the TPI-derived unique parameter terahertz electric field peak strength (TEFPS) provided spatial distribution of surface density/roughness information on core tablets, which helped in estimating tablet abrasion risk prior to film coating and predicting the location of the defects. TPI also revealed the relationship between surface strength and blending condition and is a nondestructive, quantitative approach to aid formulation development and quality control that can reduce visible surface defect risk in tablets.

Development of a novel therapeutic approach using a retinoic acid-loaded microneedle patch for seborrheic keratosis treatment and safety study in humans.

Seborrheic keratosis is one of the most common skin benign tumors in humans with a high occurrence rate of 80%-100% in people > 50 years of age; however, its pathogenesis is still unclear. The standard treatment includes cryotherapy and laser surgery for physically removing lesions. Drug therapy for this condition has not been well established. We aimed to evaluate the use of all-trans retinoic acid (ATRA)-loaded microneedle (MN) patches as a simple, alternative therapeutic option to traditional surgical treatments. This therapeutic strategy was designed to induce the proliferation of basal keratinocytes and accelerate stratum corneum turnover, leading to the lesion falling off the surface of the skin. The MN patch induced epidermal hyperplasia and marked expression of heparin-binding epidermal growth factor-like growth factor mRNA and protein corresponding to ATRA activity in the skin of HR-1 hairless mice. The acceleration of stratum corneum turnover was also observed by the dansyl chloride method. The skin irritation study in mice and safety study in humans support the safety findings of our study. Overall, MN patches can offer an effective and safe means of ATRA delivery into the skin, and the ATRA-loaded MN patch appears to be an effective pharmaceutical product providing a novel therapeutic option for seborrheic keratosis.

Quantitative analysis of the layer separation risk in bilayer tablets using terahertz pulsed imaging.

Layer separation is a critical defect in many bilayer tablets. Despite its importance for product quality, few studies have investigated its root cause. We evaluated bilayer tablets with varying layer separation tendencies using terahertz pulsed imaging (TPI) in comparison with other analytical methods such as tensile strength measurements, friability testing, scanning electron microscopy (SEM), and X-ray computed tomography (XRCT). The layer separation risk was determined by friability testing and shown to be correlated with the final compression pressure used for bilayer tablet fabrication. TPI could nondestructively detect cracks between the component layers that lead to layer separation. The adhesion integrity of the interface was quantified by the interface index, a unique value derived from the time-domain terahertz waveform. The interface index showed good correlation to the layer separation tendency and could distinguish interface quality among seven batches of bilayer tablets. In contrast, SEM and XRCT detected structural defects but could not distinguish batches with high or low layer separation risk. TPI revealed the relationship between compression pressure and interface quality. Thus, TPI can aid in quality control by providing a precise estimate of the layer separation risk and robust quality of bilayer tablet development with better understanding of layer separation.

Performance and characteristics evaluation of a sodium hyaluronate-based microneedle patch for a transcutaneous drug delivery system.

The MicroHyala(®) microneedle (MN) patch was developed to provide a simple, safe, and effective drug delivery system. In this study, we examined the performance and characteristics of our fabricated MN patch to identify potential quality issues with future commercial application. Mechanical failure force analysis identified that the strength of the MN patch was affected by environmental humidity, because higher moisture levels weakened the strength of the MN. Incorporation of all-trans retinoic acid (ATRA) or ovalbumin (OVA) into the MN patch decreased the mechanical failure force by almost 50% of the strength of placebo (without drug) patches. ATRA-loaded MN patches displayed good stability after storage at 4 °C, with more than 90% and 85% of the drug remaining in the patch after 8 and 24 weeks of storage, respectively. Tetanus toxoid- and diphtheria toxoid-loaded MN patches stored for 12 months induced robust antigen-specific immune responses similar to the responses by freshly prepared MN patches. Fluorescence imaging findings suggested that prolonged antigen deposition was induced by MN-mediated fluorescein isothiocyanate-labeled (FITC)-OVA vaccination. Overall, although the strength of MN requires improvement, our developed MN patch appears to be an effective pharmaceutical product providing a simple, safe, and relatively painless approach.

Bacillus Calmette-Guérin vaccination using a microneedle patch.

Tuberculosis (TB) caused by Mycobacterium tuberculosis continues to be a leading cause of mortality among bacterial diseases, and the bacillus Calmette-Guérin (BCG) is the only licensed vaccine for human use against this disease. TB prevention and control would benefit from an improved method of BCG vaccination that simplifies logistics and eliminates dangers posed by hypodermic needles without compromising immunogenicity. Here, we report the design and engineering of a BCG-coated microneedle vaccine patch for a simple and improved intradermal delivery of the vaccine. The microneedle vaccine patch induced a robust cell-mediated immune response in both the lungs and the spleen of guinea pigs. The response was comparable to the traditional hypodermic needle based intradermal BCG vaccination and was characterized by a strong antigen specific lymphocyte proliferation and IFN-γ levels with high frequencies of CD4(+)IFN-γ(+), CD4(+)TNF-α(+) and CD4(+)IFN-γ(+)TNF-α(+) T cells. The BCG-coated microneedle vaccine patch was highly immunogenic in guinea pigs and supports further exploration of this new technology as a simpler, safer, and compliant vaccination that could facilitate increased coverage, especially in developing countries that lack adequate healthcare infrastructure.