Various synthetic approaches were explored towards the preparation of poly(N-substituted glycine) homo/co-polymers (a.k.a. polypeptoids). In particular, monomers that would facilitate in the preparation of bio-relevant polymers via either chain- or step-growth polymerization were targeted. A 3-step synthetic approach towards N-substituted glycine N-carboxyanhydrides (NNCA) was implemented, or developed, and optimized allowing for an efficient gram scale preparation of the aforementioned monomer (chain-growth). After exploring several solvents and various conditions, a reproducible and efficient ring-opening polymerization (ROP) of NNCAs was developed in benzonitrile (PhCN). However, achieving molecular weights greater than 7 kDa required longer reaction times (>4 weeks) and sub-sequentially allowed for undesirable competing side reactions to occur (eg. zwitterion monomer mechanisms). A bulk-polymerization strategy provided molecular weights up to 11 kDa within 24 hours but suffered from low monomer conversions (ca. 25%). Likewise, a preliminary study towards alcohol promoted ROP of NNCAs suffered from impurities and a suspected alternative activated monomer mechanism (AAMM) providing poor inclusion of the initiator and leading to multi-modal dispersed polymeric systems. The post-modification of poly(N-allyl glycine) via thiol-ene photo-addition was observed to be quantitative, with the utilization of photo-initiators, and facilitated in the first glyco-peptoid prepared under environmentally benign conditions. Furthermore, poly(N-allyl glycine) demonstrated thermo-responsive behavior and could be prepared as a semi-crystalline bio-relevant polymer from solution (ie. annealing). Initial efforts in preparing these polymers via standard poly-condensation protocols were insufficient (step-growth). However, a thermally induced side-product, diallyl diketopiperazine (DKP), afforded the opportunity to explore photo-induced thiol-ene and acyclic diene metathesis (ADMET) polymerizations. Thiol-ene polymerization readily led to low molecular weight polymers (<2.5 kDa), that were insoluble in most solvents except heated amide solvents (ie. DMF), whereas ADMET polymerization, with diallyl DKP, was unsuccessful due to a suspected 6 member complexation/deactivation state of the catalyst. This understanding prompted the preparation of elongated DKPs most notably dibutenyl DKP. SEC data supports the aforementioned understanding but requires further optimization studies in both the preparation of the DKP monomers and following ADMET polymerization. This work was supported by NMR, GC-MS, FT-IR, SEC-IR, and MALDI-Tof MS characterization. Polymer properties were measured by UV-Vis, TGA, and DSC. / Die Annehmlichkeiten des Alltags und das hohe Alter das Menschen in der heutigen Zeit erreichen sind ein Ergebnis des wissenschaftlichen und technologischen Fortschritts. Insbesondere in der Medizin haben die Entwicklung neuartiger Medikamente und Therapien, künstlicher Knochen und Gewebeteile sowie der Einsatz von neuen Geräten für die Diagnostik und Assistenz bei Operationen enorm zu diesen Errungenschaften beigetragen. Jede Entwicklung fundierte letztlichen auf den Ergebnissen der Grundlagenforschung sei es von Mikro-/biologen (Identifikation anormalen Verhaltens), Biochemikern (Identifikation von Auslösern und Wirkzentren) Bio-/ organischen Chemikern (Synthese von Makro-/molekülen), Material-/chemikern (Materialsynthese) und/oder Ingenieuren/Mathematikern/Physikern (theoretischen Modelle und Berechnungen). Biomedizinische Anwendungen wie z.B. Biosensoren, künstliche Gewebeteile und Trägersubstanzen zur gezielten Wirkstofffreisetzung sind von besonderem Interesse. Materialien, die nach Kontakt mit einer Zelloberfläche in der Lage sind definiert ihre Struktur oder mechanischen Eigenschaften zu verändern und anschließend bioabbaubar sind ohne toxische Nebenwirkungen zu entfalten befriedigen die zuvor genannten Bedürfnisse. Organismen entwickeln Biomaterialien bereits seit Millionen von Jahren und sind daher ein typischer Startpunkt für die Inspiration zu vielversprechenden Substanzen. Peptoide, als Mimetika von Peptiden, werden bereits längerem von Bio-/chemikern synthetisiert und auf ihren therapeutischen Nutzen hin, neuerdings auch auf ihre Materialeigenschaften untersucht. Grundlegende Eigenschaften dieser Materialien sind ihre Biokompatibilität, kontrollierte Bioabbaubarkeit, thermische Prozessierbarkeit sowie ihre Fähigkeit zur Selbstorganisation in höher geordnete Strukturen. Die sequenzdefinierte Synthese ist jedoch aufwendig und teuer. In dieser Arbeit habe ich ein alternatives Herstellungsverfahren (Ringöffnungspolymerisation) entwickelt mit dem es möglich ist hochmolekulare Substanzen - genannt poly(N-substituierte Glycine) – herzustellen. Ich erwarte, dass diese Materialien ähnliche stimulus responsive und thermische Eigenschaften wie Polypeptide, die bereits intensiv auf ihre biomedizinische Anwendbarkeit untersucht werden, haben. Im Vergleich zu den strukturgleichen Peptiden erwarte ich eine höhere Biokompatibilität sodass diese Materialen eine vielversprechende neue Klasse biorelevanter Materialien darstellen könnte. Die fundamentalen Ergebnisse dieser Arbeit stellen eine Alternative zu den bekannten Methoden zur Herstellung poly(N-substituierter Glycine) dar. Selbige weisen stimulus responsives Verhalten und thermische Prozessierbarkeit auf, das vergleichbar ist mit bereits bekannten Materialien. Darüber hinaus erlauben sie die einfache und vielseitige Funktionalisierung für vielschichtige Anwendungen.

Supersaturating formulations have become a popular approach for enhancing the oral bioavailability of poorly water-soluble drugs. These formulation strategies can increase the intraluminal concentration by generating and maintaining supersaturation, which provides an enhanced driving force for <i>in vivo</i> absorption. Due to their inherent metastability however, crystallization in these systems can occur, negatively impacting their bioperformance. Therefore, it is critical to characterize the phase behavior and crystallization tendency of supersaturated solutions under biorelevant conditions in order to assess their potential for maximized oral absorption. Biorelevant media are commonly employed to simulate the presence of bile salts and phospholipids found in the human intestinal fluids. Currently, there is little knowledge of how simulated and aspirated intestinal media can impact the complex phase behavior of supersaturated solutions. More importantly, commonly-used simulated media rely on oversimplified recipes in terms of bile salt composition. As a result, comprehensive understanding of how well simulated media correlate with aspirated media with respect to supersaturation stability and phase transition outcomes, is still lacking. The work presented within this thesis aims to address the knowledge gap by assessing the phase behavior of supersaturated solutions using complementary analytical approaches. Depending on the type of medium used to evaluate supersaturation, variations in solubility, supersaturation thermodynamics and crystallization kinetics can be observed. This understanding can aid future efforts to optimize simulated media, design supersaturating formulations and predict their <i>in vivo</i> performance.

Dissolution testing and physiological based pharmacokinetic modeling are the essential methods during drug development. However, there is a lack of a sound approach and understanding of the parameter that controls dissolution and absorption of amorphous formulations. Robust dissolution conditions and setup and PBPK models that have a predictability of in vivo results will expedite and facilitate the drug development process. In this project, cefuroxime axetil, CA (Zinnat® as the amorphous formulations); itraconazole, ITR (Sporanox® as the amorphous formulation) and a compound undergoing clinical trial, Compound X, CX (CX tablet as the amorphous formulation) were chosen. The design of experiments for the in vitro dissolution studies using different apparatus, media and setup which closely simulate the physiological condition of humans (CA and ITR) and dogs (CX) were implemented. The dissolution of CA, ITR and CX formulations was successfully characterised using different dissolution apparatus, setting and media (compendial, biorelevant and modified media) to simulate the changes of pH, contents, hydrodynamic conditions (flow rate and rotation speed) in human gastrointestinal tract (fasted and fed state). The change of hydrodynamics combined with media change that corresponded to the physiological conditions created with USP apparatus 4 and biorelevant dissolution media were able to mimic the in vivo performance of the tested formulations. Furthermore, surface UV dissolution imaging methodology that could be used to understand the mechanism of CA and ITR (Active compounds and their amorphous formulations) dissolution were developed in this project. The UV images developed using surface UV imaging apparatus provided a visual representation and a means for the qualitative as well as quantitative assessment of the differences in dissolution rates and concentration for the model compounds used. In this project, validated PBPK models for fasted state (CA, ITR) and fed state (CA, ITR and CX) were developed. These models incorporated in vitro degradation, particle size distribution, in vitro solubility and dissolution data as well as in vivo human/ dog pharmacokinetics data. Similarly, the results showed that level A IVIVCs for all three model compounds were successfully established. Dissolution profiles with USP apparatus 4 combined with biorelevant media showed close correlation with the in vivo absorption profiles. Overall, this project successfully provides a comprehensive biorelevant methodology to develop PBPK models and IVIVCs for orally administered amorphous formulations.

Biorelevant in vitro release/dissolution tests are designed to predict the in vivo behavior of a drug and are crucial in understanding its in vivo performance. Currently, there is no standardized compendial in vitro release testing methods or regulatory guidance’s for release/dissolution testing of implants due to their complex physiological locations.Furthermore, existing compendial methods do not capture the local release profile of ‘novel’ parenterals in physiological low fluid volume surrounding areas. Long acting and in situ forming implants with orthobiologic proteins and peptides have increased over the past few decades due to a better understanding of genetic engineering. One of these products, INFUSE® Bone Graft (Medtronics, MN, USA), is an implant which helps in bone regeneration at the trauma site and is comprised of a) an absorbable collagen sponge (ACS) and b) recombinant human bone morphogenetic protein-2 (rhBMP-2). INFUSE® Bone Graft is an FDA approved product for acute, open shaft tibial fractures, lumbar spinal fusions and sinus or ridge augmentations in the jaws. The evaluation of implant products such as INFUSE® Bone Graft requires a good understanding of local and systemic release in vivo in order to ensure safe, effective, and predictable product performance. The primary goal of this study is to develop a predictive ‘biorelevant’ release model, which factors in clinically relevant physiological parameters suitable for studying and effectively predicting extended release of implants, using INFUSE Bone Graft® as our model implant. A novel biorelevant in vitro model was designed and tested. The model was observed to be discriminatory between two different carrier formulations of rhBMP-2 using a model independent approach - similarity factor (f2). Additionally, a high throughput assay to quantify rhBMP-2 release using high performance liquid chromatography with UV/VIS detection was also developed and validated. Successful completion of this study facilitated an in vitro release study design that incorporated the complex biorelevant parameters of implant dosage forms, the model will offer crucial insights into biological performance, and aid in developing methods to characterize release of other similar dosage forms.

In vitro dissolution, release and permeation testing is a common practice during drug product research and development. These in vitro tests, if predictive, are referred to as biorelevant tests and can play diverse roles to facilitate and expedite product development in a cost effective manner. Oral transmucosal products (OTPs) are currently tested using compendial and modified in vitro tests which may or may not be good predictors of in vivo performance due to a lack of biorelevance. A critical need for a broadly applicable and biorelevant in vitro system for OTPs has been expressed in the literature and the goal of this research was the development and validation of a biorelevant in vitro method that can facilitate accurate prediction of the in vivo behavior of OTPs. A combined strategy of appropriate apparatus design and relevant physiological and in vitro variable adjustment was investigated to incorporate biorelevance into evaluation of OTPs. A novel in vitro device, the bidirectional transmucosal apparatus (BTA), was designed and fabricated which allowed simulation of the oral cavity and its physiological variables to evaluate OTPs in a more realistic fashion. The BTA was tested using snus (a type of smokeless tobacco) as the OTP product. A simple and selective high performance liquid chromatographic (HPLC) method with photodiode array (PDA) detection was developed and validated to assess in vitro nicotine release and permeation (Linearity: 0.5 – 32 μg/mL; calibration curve accuracy (%recovery, n=5 ): 97.98-103.20%; calibration curve precision (%RSD, n=5): 0.15-3.14%). The performance of BTA was compared with the modified USP IV flow through apparatus (USP IV) and a commercially available vertical diffusion cell (VDC). The observed in vitro in vivo relationship (IVIVR) slopes with the USP IV, VDC and BTA were 0.27, 2.01 and 2.11 respectively. The BTA was selected over the VDC and USP IV devices because of better simulation and adjustment of variables to incorporate biorelevance in the test of OTPs. Additionally, the BTA allows study of permeation and release simultaneously unlike VDC and USP IV apparatuses. Further, the different BTA parameters were sequentially screened for their impact on in vitro rate of nicotine permeation that can be employed for the optimization of IVIVR for snus. Based on the results, stimulated saliva swallowing rate (SSSR) and media temperature were considered as significant factors affecting in vitro permeation of nicotine and used to further optimize IVIVR for snus. A 32 multifactorial experimental design integrating SSSR (0.32, 1.66 and 3 mL/min) and media temperature (25, 37 and 45 °C) was employed. Based on the response surface analysis, 0.55 mL/min SSSR and 43 °C media temperature were identified as optimal BTA conditions that would give perfect IVIVR (i.e. IVIVR slope close to one) for snus. The experimental value of IVIVR slope (0.92) at these optimal conditions indicated that the BTA is a valid in vitro system for evaluation of OTPs in a biorelevant manner. The applicability of BTA for predicting nicotine permeation from ‘Stonewall’, a dissolvable compressed tobacco was also evaluated. However, comparable in vitro nicotine permeation and in vivo nicotine absorption profiles were not obtained (ratio of in vitro permeation to in vivo absorption rate ranged from 0.04 to 0.14 at different in vitro conditions) either due to the unavailability of reliable clinical data or due to inherently different in vivo behavior of Stonewall compared to snus that would require further modification in the BTA. In conclusion, this research demonstrated the potential of the novel in vitro device to be a valuable tool for the prediction of in vivo performance of snus. The application of the novel bidirectional transmucosal apparatus for other types of OTPs will be an interesting subject for further investigation.