Genesis, mechanism, and avoidance of cosmetic coating defects - An industrial case study.

Film-coated tablets as solid oral dosage forms are a well-accepted way of administering drugs but are not without specific challenges during manufacturing. One relevant criterion of the final product is the visual integrity and therewith, the absence of cosmetic optical defects such as edge chipping. The aim of the present study was to examine the origin of those edge chipping defects, which were observed during commercial manufacturing of film-coated tablets, and to provide recommendations for process optimization to reduce the defect occurrence. The unraveling of the herein described phenomenon necessitated an interplay of in-depth material characterization, discrete element modeling (DEM) as well as an in-house developed optical measurement system for the automated quantification of tablet defects. As a result of this investigation, the automatic unloading step after the tablet coating process was identified as the most critical step for the occurrence of chipping defects and a replacement by manual unloading was proposed to reduce the defect propensity. The recommended optimization was subsequently confirmed in several manufacturing runs and a reduction of defect propensity by a factor of 5 was observed, highlighting the relevance and the impact of the performed thorough investigation.

Acid-induced degradation of widely used NIR dye DiR causes hypsochromic shift in fluorescence properties.

DiR (1,1'-dioctadecyl-3,3,3',3'-tetramethylindotricarbocyanine iodide) is one of the most widely used near-infrared dyes for in-vivo imaging due to its favorable optical properties. So far, chemical stability has been taken for granted by most investigators. However, in a recently published imaging study, we found that DiR can exert a hypsochromic shift in fluorescence in-vivo, potentially induced by low pH. This behavior may disturb kinetic measurements and the readout of additional markers fluorescing at lower wavelengths. The present in-vitro experiments were conducted to verify the findings from our in-vivo study and to elucidate the changes of the optical properties of DiR. For this purpose, DiR was incubated in a pH range from pH 2 to neutral pH over 42 days. Fluorescence and absorption measurements as well as mass spectrometry analytics (MS) were conducted to monitor the degradation process of DiR. The protonation effect on DiR optical behavior was estimated using in-silico modelling. For the most acidic sample, a distinct decrease in DIR-fluorescence was noted and several degradation products could be analyzed via MS, confirming the initial hypothesis. Ultimately, scientists should be aware of the possibility of acid-induced DiR degradation, especially when adding a second fluorescence label for dual dye imaging or performing quantitative data analysis.

Dual dye in-vivo imaging of differentially charged PLGA carriers reveals antigen-depot effect, leading to improved immune responses in preclinical models.

The present in-vivo study investigated the behavior and performance of differently charged poly(lactic­co­glycolic) acid microparticles (PLGA MP) as vaccination platform. For this purpose, particles loaded with ovalbumin (OVA) as model antigen were subcutaneously (s.c.) injected in SKH1 mice. The utilized SKH1 hairless mice exhibit a fully operative immune system and allow parallel imaging investigations due to the lack of hair. Usage of this species enabled the combination of two investigations within a single study protocol, namely noninvasive in-vivo imaging and immune responses directed towards the antigen. All treatments were well tolerated, no safety drop-outs occurred. The fate of the model antigen OVA as well as the PLGA particles was monitored using a dual dye approach (CF660C & DiR) by multispectral fluorescence imaging (msFI). A depot effect for the OVA antigen adsorbed to the MP surface could be observed for the positively charged MPs. The immune response against OVA was then analyzed. OVA alone did not induce an immune response, whereas the positively charged as well as the neutral MP induced a strong and consistent humoral immune response with a clear favor of IgG1 over IgG2a subclass antibodies. In contrast, negatively charged MP were not able to induce measurable antibody responses. Cellular immune response was weak and inconsistent for all treated groups, which verifies previous in-vitro results conducted with the herein described microparticulate antigen platform. In conclusion, the characterization of the in-vivo performance yielded valuable information about antigen and carrier fate after application. The presented adjuvant platform is capable of inducing strong TH2 dominated immune responses characterized by enhanced IgG1 subclass titers which are critical for vaccines aimed at promoting induction of neutralizing antibodies.

Combining R-DOTAP and a particulate antigen delivery platform to trigger dendritic cell activation: Formulation development and in-vitro interaction studies.

The utilization of the cationic lipid R-DOTAP as immune cell stimulant (e.g. its stimulating effects on immature dendritic cells) and correspondingly as possible adjuvant for vaccination is well known. Likewise, it is described in literature that solid polymer particles loaded with antigens can be size-tailored in a manner to be suitable for phagocytosis by antigen presenting cells. The effects of DOTAP-microparticle combinations, however, are not well understood. This study aimed therefore to explore the potential of R-DOTAP stabilized microparticles (MP) to act as a carrier platform for antigens e.g. for cancer vaccination. It was investigated whether or not a combination of R-DOTAP and PLGA leads to a boosted adjuvant effect in dendritic cell maturation. For proper comparison, neutral and negatively charged MPs of comparable sizes were developed. Toxicity, uptake, routing and maturation of the MP platform was assessed in-vitro on human immature dendritic cells (iDCs). Interestingly, none of the tested placebo formulations (without antigen) was capable to induce DC maturation when compared to LPS as positive control. This is in contrast to experiments previously reported in literature, where R-DOTAP (e.g. in liposomal form) triggered iDC maturation even without antigen. Possible reasons and further approaches are discussed in the paper.

Investigation of the stabilizer elimination during the washing step of charged PLGA microparticles utilizing a novel HPLC-UV-ELSD method.

Quantification of stabilizer content in microparticles and other products is of great importance for formulation development, drug product quality control as well as for reproducible manufacturing. A fast and sensitive HPLC method with evaporative light scattering detection (ELSD) capable of detecting docusate sodium (DOSS), poly (lactic-co-glycolic acid) (PLGA; Resomer RG 503 H) and R-1,2-dioleoyloxy-3-trimethylammonium-propane (DOTAP) in a single run was successfully developed. In contrast to previously described methods, hydrolysis of PLGA as pretreatment is not necessary, thereby enabling accurate quantification of stabilizer next to the intact matrix polymer. This method was used to investigate the impact of washing procedures of polymeric microparticles manufactured either with anionic stabilizer DOSS or with cationic stabilizer DOTAP. High amounts of DOSS were detected in the washing water. This finding was consistent with the result that no DOSS could be detected in the washed and dried microparticles (