Tailored Polymersomes for Enhanced Oral Drug Delivery: pH-Sensitive Systems for Intestinal Delivery of Immunosuppressants.

Ensuring precise drug release at target sites is crucial for effective treatment. Here, pH-responsive nanoparticles for oral administration of mycophenolate mofetil, an alternative therapy for patients with inflammatory bowel disease unresponsive to conventional treatments is developed. However, its oral administration presents challenges due to its low solubility in the small intestine and high solubility and absorption in the stomach. Therefore, this aim is to design a drug delivery system capable of maintaining drug solubility compared to the free drug while delaying absorption from the stomach to the intestine. Successful synthesis and assembly of a block copolymer incorporating a pH-responsive functional group is achieved. Dynamic light scattering indicated a significant change in hydrodynamic size when the pH exceeded 6.5, confirming successful incorporation of the pH-responsive group. Encapsulation and controlled release of mycophenolate mofetil are efficiently demonstrated, with 90% release observed at intestinal pH. In vitro cell culture studies confirmed biocompatibility, showing no toxicity or adverse effects on Caco-2 cells. In vivo oral rat studies indicated reduced drug absorption in the stomach and enhanced absorption in the small intestine with the developed formulation. This research presents a promising drug delivery system with potential applications in the treatment of inflammatory bowel disease.

Methotrexate Detection in Serum at Clinically Relevant Levels with Electrochemically Assisted SERS on a Benchtop, Custom Built Raman Spectrometer.

Therapeutic drug monitoring (TDM) is an essential clinical practice for optimizing drug dosing, thereby preventing adverse effects of drugs with a narrow therapeutic window, slow clearance, or high interperson pharmacokinetic variability. Monitoring methotrexate (MTX) during high-dose MTX (HD-MTX) therapy is necessary to avoid potentially fatal side effects caused by delayed elimination. Despite the efficacy of HD-MTX treatment, its clinical application in resource-limited settings is constrained due to the relatively high cost and time of analysis with conventional analysis methods. In this work, we developed (i) an electrochemically assisted surface-enhanced Raman spectroscopy (SERS) method for detecting MTX in human serum at a clinically relevant concentration range and (ii) a benchtop, Raman detection system with an integrated potentiostat, software, and data analysis unit that enables mapping of small areas of SERS substrates and quantitative SERS-based analysis. In the assay, by promoting electrostatic attraction between gold-coated nanopillar SERS substrates and MTX molecules in aqueous samples, a detection limit of 0.13 µM with a linear range of 0.43-2 µM was achieved in PBS. The implemented sample cleanup through gel filtration proved to be highly effective, resulting in a similar detection limit (0.55 µM) and linear range (1.81-5 µM) for both PBS and serum. The developed and optimized assay could also be used on the in-house built, Raman device. We showed that MTX detection can be carried out in less than 30 min with the Raman device, paving the way toward the TDM of MTX at the point-of-need and in resource-limited environments.

Design of a self-unfolding delivery concept for oral administration of macromolecules.

Delivering macromolecular drugs, e.g. peptides, to the systemic circulation by oral administration is challenging due to their degradation in the gastrointestinal tract and low transmucosal permeation. In this study, the concept of an oral delivery device utilizing an elastomeric material is presented with the potential of increasing the absorption of peptides, e.g. insulin. Absorption enhancement in the intestine is proposed as a result of self-unfolding of a polydimethylsiloxane foil upon release from enteric coated capsules. A pH-sensitive polymer coating prevents capsule disintegration until arrival in the small intestine where complete unfolding of the elastomeric foil ensures close contact with the intestinal mucosa. Foils with close-packed hexagonal compartments for optimal drug loading are produced by casting against a deep-etched silicon master. Complete unfolding of the foil upon capsule disintegration is verified in vitro and the insulin release profile of the final delivery device confirms insulin protection at gastric pH. In vivo performance is evaluated with the outcome of quantifiable plasma insulin concentrations in all rats receiving duodenal administration of the novel delivery device. By taking advantage of elastomeric material properties for drug delivery, this approach might serve as inspiration for further development of commercially viable biocompatible devices for oral delivery of macromolecules.

Temperature-Modulated Micromechanical Thermal Analysis with Microstring Resonators Detects Multiple Coherent Features of Small Molecule Glass Transition.

Micromechanical Thermal Analysis utilizes microstring resonators to analyze a minimum amount of sample to obtain both the thermal and mechanical responses of the sample during a heating ramp. We introduce a modulated setup by superimposing a sinusoidal heating on the linear heating and implementing a post-measurement data deconvolution process. This setup is utilized to take a closer look at the glass transition as an important fundamental feature of amorphous matter with relations to the processing and physical stability of small molecule drugs. With an additionally developed image and qualitative mode shape analysis, we are able to separate distinct features of the glass transition process and explain a previously observed two-fold change in resonance frequency. The results from this setup indicate the detection of initial relaxation to viscous flow onset as well as differences in mode responsivity and possible changes in the primary resonance mode of the string resonators. The modulated setup is helpful to distinguish these processes during the glass transition with varying responses in the frequency and quality factor domain and offers a more robust way to detect the glass transition compared to previously developed methods. Furthermore, practical and theoretical considerations are discussed when performing measurements on string resonators (and comparable emerging analytical techniques) for physicochemical characterization.

Design of Hierarchical Surfaces for Tuning Wetting Characteristics.

Patterned surfaces with tunable wetting properties are described. A hybrid hierarchical surface realized by combining two different materials exhibits different wetting states, depending on the speed of impingement of the water droplets. Both "lotus" (high contact angle and low adhesion) and "petal" (high contact angle and high adhesion) states were observed on the same surface without the need of any modification of the surface. The great difference between the capillary pressures exerted by the microstructures and nanostructures was the key factor that allowed us to tailor effectively the adhesiveness of the water droplets. Having a low capillary pressure for the microstructures and a high capillary pressure for the nanostructures, we allow to the surface the possibility of being in a lotus state or in a petal state.

Thermophoretic forces on DNA measured with a single-molecule spring balance.

We stretch a single DNA molecule with thermophoretic forces and measure these forces with a spring balance: the DNA molecule itself. It is an entropic spring which we calibrate, using as a benchmark its Brownian motion in the nanochannel that contains and prestretches it. This direct measurement of the thermophoretic force in a static configuration finds forces up to 130 fN. This is eleven times stronger than the force experienced by the same molecule in the same thermal gradient in bulk, where the molecule shields itself. Our stronger forces stretch the middle of the molecule up to 80% of its contour length. We find the Soret coefficient per unit length of DNA at various ionic strengths. It agrees, with novel precision, with results obtained in bulk for DNA too short to shield itself and with the thermodynamic model of thermophoresis.

Light-induced local heating for thermophoretic manipulation of DNA in polymer micro- and nanochannels.

We present a method for making polymer chips with a narrow-band near-infrared absorber layer that enables light-induced local heating of liquids inside fluidic micro- and nanochannels fabricated by thermal imprint in polymethyl methacrylate. We have characterized the resulting liquid temperature profiles in microchannels using the temperature dependent fluorescence of the complex [Ru(bpy)(3)](2+). We demonstrate thermophoretic manipulation of individual YOYO-1 stained T4 DNA molecules inside micro- and nanochannels.

Stretching DNA in polymer nanochannels fabricated by thermal imprint in PMMA.

We present results regarding the fast and inexpensive fabrication of polymer biochips for investigating the statics and dynamics of DNA confined in nanochannels. The biochips have been fabricated by means of nanoimprint lithography (NIL) in low molecular weight polymethyl methacrylate (PMMA) using a 4 inch diameter two-level hybrid stamp. The fluidic structures were sealed using thermal polymer fusion bonding. The stamp has nanometer- and micrometer-sized protrusions defined in a thermally grown SiO(2) layer and the sol-gel process derived duromeric hybrid polymer Ormocomp, respectively. The stamp is compatible with molecular vapor deposition (MVD), used for applying a durable chlorosilane based antistiction coating, and allows for imprint up to a temperature of 270 °C. The extension of YOYO-1 stained T4 GT7 bacteriophage DNA inside the PMMA nanochannels has been experimentally investigated using epi-fluorescence microscopy. The measured average extension length amounts to 20% of the full contour length with a standard deviation of 4%. These results are in good agreement with results obtained by stretching DNA in conventional fused silica nanochannels.