@phdthesis{Hanio2024,
  author    = {Hanio, Simon},
  title     = {The impact of bile on intestinal permeability of drug substances},
  doi       = {10.25972/OPUS-34890},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-348906},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2024},
  abstract  = {Most medicines are taken orally. To enter the systemic circulation, they dissolve in the intestinal fluid, cross the epithelial barrier, and pass through the liver. Intestinal absorption is driven by the unique features of the gastrointestinal tract, including the bile colloids formed in the lumen and the mucus layer covering the intestinal epithelium. Neglecting this multifaceted environment can lead to poor drug development decisions, especially for poorly water-soluble drugs that interact with bile and mucus. However, there is a lack of a rationale nexus of molecular interactions between oral medicines and gastrointestinal components with drug bioavailability. Against this background, this thesis aims to develop biopharmaceutical strategies to optimize the presentation of oral therapeutics to the intestinal epithelial barrier. In Chapter 1, the dynamics of bile colloids upon solubilization of the poorly-water soluble drug Perphenazine was studied. Perphenazine impacted molecular arrangement, structure, binding thermodynamics, and induced a morphological transition from vesicles to worm-like micelles. Despite these dynamics, the bile colloids ensured stable relative amounts of free drug substance. The chapter was published in Langmuir. Chapter 2 examined the impact of pharmaceutical polymeric excipients on bile-mediated drug solubilization. Perphenazine and Imatinib were introduced as model compounds interacting with bile, whereas Metoprolol did not. Some polymers altered the arrangement and geometry of bile colloids, thereby affecting the molecularly soluble amount of those drugs interacting with bile. These insights into the bile-drug-excipient interplay provide a blueprint to optimizing formulations leveraging bile solubilization. The chapter was published in Journal of Controlled Release. Chapter 3 deals with the impact of bile on porcine intestinal mucus. Mucus exposed to bile solution changed transiently, it stiffened, and the overall diffusion rate increased. The bile-induced changes eased the transport of the bile-interacting drug substance Fluphenazine, whereas Metoprolol was unaffected. This dichotomous pattern was linked to bioavailability in rats and generalized based on two previously published data sets. The outcomes point to a bile-mucus interaction relevant to drug delivery. The chapter is submitted. The Appendix provides a guide for biopharmaceutical characterization of drug substances by nuclear magnetic resonance spectroscopy aiming at establishing a predictive algorithm. In summary, this thesis deciphers bile-driven mechanisms shaping intestinal drug absorption. Based on these molecular insights, pharmaceuticals can be developed along a biopharmaceutical optimization, ultimately leading to better oral drugs of tomorrow.},
  subject      = {Solubilisation},
  language  = {en}
}
@phdthesis{Schlauersbach2023,
  author    = {Schlauersbach, Jonas},
  title     = {The bile-drug-excipient interplay},
  doi       = {10.25972/OPUS-29653},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-296537},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {The bile system in vertebrates is an evolutionary conserved endogenous solubilization system for hydrophobic fats and poorly water-soluble vitamins. Bile pours out from the gallbladder through the common bile duct into the duodenum triggered by cholecystokinin. Cholecystokinin is released from enteroendocrine cells after food intake. The small intestine is also the absorption site of many orally administered drugs. Most emerging drug candidates belong to the class of poorly water-soluble drugs (PWSDs). Like hydrophobic vitamins, these PWSDs might as well be solubilized by bile. Therefore, this natural system is of high interest for drug formulation strategies. Simulated intestinal fluids containing bile salts (e.g., taurocholate TC) and phospholipids (e.g., lecithin L) have been widely applied over the last decade to approximate the behavior of PWSDs in the intestine. Solubilization by bile can enhance the oral absorption of PWSDs being at least in part responsible for the positive "food effect". The dissolution rate of PWSDs can be also enhanced by the presence of bile. Furthermore, some PWSDs profit from supersaturation stabilization by bile salts. Some excipients solubilizing PWSDs seemed to be promising candidates for drug formulation when investigated in vitro without bile. When tested in vivo, these excipients reduced the bioavailability of drugs. However, these observations have been hardly examined on a molecular level and general links between bile interaction in vitro and bioavailability are still missing. This thesis investigated the interplay of bile, PWSDs, and excipients on a molecular level, providing formulation scientists a blueprint for rational formulation design taking bile/PWSD/excipient/ interaction into account. The first chapter focus on an in silico 1H nuclear magnetic resonance (NMR) spectroscopy-based algorithm for bile/drug interaction prediction. Chapter II to IV report the impact of excipients on bioavailability of PWSDs interacting with bile. At last, we summarized helpful in vitro methods for drug formulation excipient choice harnessing biopharmaceutic solubilization in chapter V. Chapter I applies 1H NMR studies with bile and drugs on a large scale for quantitative structure-property relationship analysis. 141 drugs were tested in simulated intestinal media by 1H NMR. Drug aryl-proton signal shifts were correlated to in silico calculated molecular 2D descriptors. The probability of a drug interacting with bile was dependent on its polarizability and lipophilicity, whereas interaction with lipids in simulated intestinal media components was dependent on molecular symmetry, lipophilicity, hydrogen bond acceptor capability, and aromaticity. The probability of a drug to interact with bile was predictive for a positive food effect. This algorithm might help in the future to identify a bile and lipid interacting drug a priori. Chapter II investigates the impact of excipients on bile and free drug fraction. Three different interaction patterns for excipients were observed. The first pattern defined excipients that interacted with bile and irreversibly bound bile. Therefore, the free drug fraction of bile interacting drugs increased. The second pattern categorized excipients that formed new colloidal entities with bile which had a high affinity to bile interacting drugs. These colloids trapped the drug and decreased the free drug fraction. The last excipient pattern described excipients that formed supramolecular structures in coexistence with bile and had no impact on the free drug fraction. These effects were only observed for drugs interacting with bile (Perphenazine and Imatinib). Metoprolol's free drug fraction, a compound not interacting with bile, was unaffected by bile or bile/excipient interaction. We hypothesized that bile/excipient interactions may reduce the bioavailability of bile interacting drugs. Chapter III addresses the hypothesis from chapter II. A pharmacokinetic study in rats revealed that the absorption of Perphenazine was reduced by bile interacting excipients due to bile/excipient interaction. The simultaneous administration of excipient patterns I and II did not further reduce or enhance Perphenazine absorption. Conversely, the absorption of Metoprolol was not impacted by excipients. This reinforced the hypothesis, that drugs interacting with bile should not be formulated with excipients also interacting with bile. Chapter IV further elaborates which in vitro methods using simulated intestinal fluids are predictive for a drug's pharmacokinetic profile. The PWSD Naporafenib was analyzed in vitro with simulated intestinal fluids and in presence of excipients regarding solubility, supersaturation, and free drug fraction. Naporafenib showed a strong interaction with TC/L from simulated bile. Assays with TC/L, but not without identified one excipient as possibly bioavailability reducing, one as supersaturation destabilizing, and the last as bile not interacting and supersaturation stabilizing excipient. A pharmacokinetic study in beagle dogs outlined and confirmed the in vitro predictions. The Appendix summarizes in vivo predictive methods as presented in chapter I to IV and rationalizes experimental design paving the way towards a biopharmaceutic excipient screening. The first presented preliminary decision tree is transformed into a step-by-step instruction. The presented decision matrix might serve as a blueprint for processes in early phase drug formulation development. In summary, this thesis describes how a drug can be defined as bile interacting or non-interacting and gives a guide as well how to rate the impact of excipients on bile. We showed in two in vivo studies that bile/excipient interaction reduced the bioavailability of bile interacting drugs, while bile non-interacting drugs were not affected. We pointed out that the bile solubilization system must be incorporated during drug formulation design. Simulated gastrointestinal fluids offer a well-established platform studying the fate of drugs and excipients in vivo. Therefore, rational implementation of biopharmaceutic drug and excipient screening steers towards efficacy of oral PWSD formulation design.},
  subject      = {Solubilisation},
  language  = {en}
}
@phdthesis{Theiss2019,
  author    = {Theiss, Christiane},
  title     = {Qualitative Charakterisierung polydisperser Macrogole sowie strukturell verwandter Hilfsstoffe mittels HPLC-CAD},
  doi       = {10.25972/OPUS-17927},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-179274},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2019},
  abstract  = {The class of macrogols and macrogol-based excipients, i.e. macrogol fatty alcohol ethers, macrogol fatty acid esters, and polysorbates, plays an important role in modern galenic formulations. Formerly used as simple emulsifiers, they are nowadays utilized in fields such as targeted drug release to increase bioavailability, and as solubilizers for complex systems. For these multifaceted applications, and regarding the polydisperse structures of the macrogols, a reproducible and significant analytical procedure is required. For the characterization of excipients, the European Pharmacopoeia (Ph. Eur.) provides some compendial protocols which are able to describe the number of functional groups present in the substance. Some examples of these bulk parameters are the hydroxyl value, the iodine value, the peroxide value, or the acid value. Thus, these bulk parameters allow an overview of the average molar weight or possible degradation processes (e.g. autoxidation), but they provide no further information about the polymeric distribution which can heavily depend on the manufacturing process. Furthermore, bulk parameter investigations are very time-consuming and prone to errors due to their stringent reaction processes and numerous reaction steps. Since several years, the HPLC has been the gold standard of pharmaceutical analytics particularly due to the fact of automation. Coupled to UV detection, it offers the opportunity for a quick, easy, and robust analysis for many drugs. In the field of excipients, the development progress of HPLC-analysis is much slower due to the fact that most excipients lack a UV-chromophore. The application of the highly sensitive mass spectrometry would be eligible for detection but is rather complex and expensive. However, the development of the aerosol-based detectors such as the ELSD (evaporative light scattering detection), the CAD (charged aerosol detection), and the NQADTM (nano quantity aerosol detection) enables the application of HPLC for analyzing non-chromophoric substances. This work aimed to develop a generic HPLC-CAD method to analyze a wide range of macrogols and macrogol-based excipients. The separation was performed on a C18-column. A gradient method was developed based upon several linear gradient steps in order to be able to separate the different chain lengths. The mobile phases were water and acetonitrile, respectively, to which 0.1\% formic acid was added. Macrogols in the average size range of PEG 300 to PEG 3000 were separated with acceptable resolution. The separation results were verified by mass spectrometry for PEG 300 - 1500. Five saturated and two non-saturated fatty acids, as well as two fatty alcohols of different chain lengths were successfully separated. 13 macrogol-based excipients were analyzed with the developed method and separated successfully. The macrogol fatty alcohol ethers, macrogol stearates, and polysorbates were separated to sufficient extent to analyze the polymeric distribution. The free PEGs in the excipients were separated and identified. Based on these free PEGs, different manufactural processes could be determined. Depending on the average chain lengths of the processed PEGs, the free fatty acids or alcohols could be identified and separated from the esters or ethers, respectively. For the smaller average chain lengths, the free fatty acids and alcohols coeluted with the esters and ethers. Macrogol glycerol hydroxy stearate (Cremophor® RH40) was separated into its components except for the linear monoesters which partially coeluted with the free PEGs, and the glycerol triesters which showed effects of size exclusion. The developed method was also used for stability tests of the non-saturated fatty acids, i.e. oleic and linoleic acid. Here, the fatty acid solutions were chemically (hydrogen peroxide) and thermally (60 °C) stressed and analyzed after different time spans. A time and temperature dependent degradation was observed. An assignment of some degradation products was performed by determining the m/z values with mass spectrometry. The method proved to be capable of separating the degradation products of the main substance and allows to estimate the dimension of degradational processes and partly identify the structures of the degradational products. In general, the provided method offers a good basis for analyzing and characterizing a wide field of substance classes. It provides an extension of bulk parameters (e.g. hydroxyl value) with a reduction of analytical effort. It offers a good starting point for more specific observations such as long-term stability or other related substance classes.},
  subject      = {HPLC},
  language  = {de}
}