Publications & Patents

Photo-responsive chemistries for user-directed hydrogel network modulation to investigate cell-matrix interactions 

Ohnsorg, M. L.*; Hushka, E. A.*; Anseth, K. A.

Accounts of Chemical Research, 2024, doi: https://doi.org/10.1021/acs.accounts.4c00548

Synthetic extracellular matrix (ECM) engineering is a highly interdisciplinary field integrating materials and polymer science and engineering, chemistry, cell biology, and medicine to develop innovative strategies to investigate and control cell-matrix interactions. Herein, we present examples of how this photochemical toolbox has been used under physiological reaction conditions with spatiotemporal control to answer important biological questions and address medical needs. Specifically, our group has exploited these materials to study mesenchymal stem cell mechanosensing and differentiation, the activation of fibroblasts in the context of valve and cardiac fibrosis, muscle stem cell response to matrix changes during injury and aging, and predictable symmetry breaking during intestinal organoid development. The materials and reactions described herein are diverse and enable the design and implementation of an array of hydrogels that can serve as cell delivery systems, tissue engineering scaffolds, or even in vitro models for studying disease or screening for new drug treatments. 

Macromers and Bottle Brush Polymers for Delivery of Biological Agents 

Reineke, T. M.; Bates, F. S.; Ohnsorg, M. L.

U.S. Patent No. 11986533, May 21st, 2024.  https://patents.justia.com/patent/11986533

A composition includes a macromolecular polyacrylamide copolymer excipient with an α-end including a ROMP-active norbornene end-group and a ω-end including a terminal monomer with an end group chosen from: a hydrogen atom (H); or a functionalized acrylate with functionality chosen from alkyl, hydroxyl (OH), methyl-polyethylene glycol ((PEG)-CH3), hydroxy-PEG (PEG-OH), carboxylic acid (COOH), and combinations thereof. A biological compound chosen from active pharmaceutical ingredients, proteins, polynucleotides, and mixtures and combinations thereof is non-covalently bound with the macromolecular excipient. 

Nonlinear Elastic Bottlebrush Polymer Hydrogels Modulate Actomyosin Mediated Protrusions in Mesenchymal Stromal Cells

Ohnsorg, M. L.; Mash, K. M.; Kang, A.; Rao, V. V.; Kirkpatrick, B. E.; Anseth, K. S.

Advanced Materials, 2024, doi: https://doi.org/10.1002/adma.202403198 

Nonlinear elastic extracellular matrix properties are difficult to recapitulate without the use of fibrous architectures, which couple strain-stiffening and stress-relaxation. Herein, bottlebrush polymer hydrogels are used to isolate and tune the strain-stiffening biomechanical feedback sensed by human mesenchymal stromal cells (hMSCs) in non-fibrous engineered microenvironments. Nonlinear elastic mechanics induces a protrusion-rich hMSC phenotype regulated by focal adhesions and actomyosin dynamics. 

Drug-Polymer Nanodroplet Formation and Morphology Drive Solubility Enhancement of GDC-0810

Barr, K. E.*; Ohnsorg, M. L.*; Liberman, L.; Corcoran, L. G.; Sarode, A.; Nagapudi, K.; Feder, C.; Bates, F. S.; Reineke, T. M.  (*authors contributed equally)

Bioconjugate Chemistry, 2024, doi: https://doi.org/10.1021/acs.bioconjchem.4c00018 

Nanodroplet formation is important to achieve supersaturation of active pharmaceutical ingredients (APIs) in an amorphous solid dispersion. The aim of the current study was to explore how polymer composition, architecture, molar mass, and surfactant concentration affect polymer–drug nanodroplet morphology with the breast cancer API, GDC-0810. The impact of nanodroplet size and morphology on dissolution efficacy and drug loading capacity was explored using polarized light microscopy, dynamic light scattering, and cryogenic transmission electron microscopy. 

Hydrophilic Surface-Modification of Cationic Unimolecular Bottlebrush Vectors Moderate pDNA and RNP Bottleplex Stability and Delivery Efficacy

Dalal, R.J.*; Ohnsorg, M. L.*; Panda, S.; Reineke, T. M. (*authors contributed equally)

Biomacromolecules, 2022, doi:https://doi.org/10.1021/acs.biomac.2c00999 

A cationic unimolecular bottlebrush polymer with chemically modified end-groups was synthesized to understand the impact of hydrophilicity on colloidal stability, nucleic acid delivery performance, and toxicity.  The bottlebrush family was preformulated with biological payloads of pDNA and CRISPR-Cas9 RNP in both water and PBS to understand binding, aggregation kinetics, cytotoxicity, and delivery efficacy. Increasing end-group hydrophilicity and preformulation of bottleplexes in PBS increased colloidal stability and cellular viability; however, this did not always result in increased transfection efficiency. The bottlebrush family exemplifies how formulation conditions, polymer loading, and end-group functionality of bottlebrushes can be tuned to balance expression with cytotoxicity ratios and result in enhanced overall performance. 

How Early-Career Scientists Responded with Resiliency to the Space Created by the COVID-19 Pandemic

Fung, F. M.; Jilani, S. Z.; Ohnsorg, M. L.; Pinals, R. L.; Saraf, M.; Tropp, J.; Carlton, P.

ACS Central Science, 2022, doi: https://doi.org/10.1021/acscentsci.2c00094 

"Beyond scientific and academic progress, the pandemic challenged us to rethink what success means and what matters most to us as individuals, such as work-life management."

Cationic Bottlebrush Polymers Outperform Linear Polycation Analogues for pDNA Delivery and Gene Expression

Dalal, R. J.; Kumar, R.; Ohnsorg, M. L.; Brown, M. E.; Reineke, T. M.

ACS Macro Letters, 2021, doi: https://doi.org/10.1021/acsmacrolett.1c00335 

Cationic polymer vehicles have emerged as promising platforms for nucleic acid delivery because of their scalability, biocompatibility, and chemical versatility. Advancements in synthetic polymer chemistry allow us to precisely tune chemical functionality with various macromolecular architectures to increase the efficacy of nonviral-based gene delivery.  Overall, a canonical cationic monomer, such as DMAEMA, synthesized in the form of cationic bottlebrush polymers proved to be far more efficient in functional pDNA delivery and expression than linear pDMAEMA. This work underscores the importance of architectural modifications and the potential of bottlebrushes to serve as effective biomacromolecule delivery vehicles. 

Bottlebrush Polymer Excipients Enhance Drug Solubility: Influence of End-Group Hydrophilicity and Thermoresponsiveness

Ohnsorg, M. L.; Prendergast, P. C.; Robinson, L. L.; Bockman, M. R.; Bates, F. S.; 

Reineke, T. M.

ACS Macro Letters, 2021, doi: https://doi.org/10.1021/acsmacrolett.0c00890 

Bottlebrush polymers have great potential as vehicles to noncovalently sequester, stabilize, and deliver hydrophobic small molecule actives. To this end, we synthesized a poly(N-isopropylacrylamide-stat-N,N-dimethylacrylamide) bottlebrush copolymer using ring-opening metathesis polymerization and developed a facile method to control the thermoresponsive properties using post-polymerization modification. Six increasingly hydrophilic end-groups were installed, yielding cloud point temperature control over a range of 22–42 °C. Solubility enhancement of the antiseizure medication, phenytoin, increased significantly with the hydrophilicity of the end-group moiety. Notably, carboxylated bottlebrush copolymers solubilized formulations with higher drug loadings than linear copolymers because they exist as unimolecular nanoparticles with a synthetically defined density of polymer chains that are more stable in solution. This work provides the first investigation of bottlebrush polymers for hydrophobic noncovalent sequestration and solubilization of pharmaceuticals. 

The above work was featured in ColorMePhD, "Polymer Parachutes"

Click HERE to access the coloring book pages!

Tuning PNIPAm Self-assembly and Thermoresponse: Roles of Hyrophobic End-Groups and Hydrophilic Comonomer

Ohnsorg, M. L.; Ting, J. D.; Jones, S.D.; Jung, S.; Bates, F. S.; Reineke, T. M.

Polymer Chemistry, 2019, doi: https://doi.org/10.1039/C9PY00180H

Modifications to the aqueous solution self-assembly and thermoresponsive properties of poly(N-isopropylacrylamide) (PNIPAm) can be achieved by hydrophobic end-group functionalization and incorporation of hydrophilic N,N-dimethylacrylamide (DMA) repeat units. These results demonstrate surprising and delicately balanced tradeoffs between short non-polar end groups and tailored hydrophobicity in the nanoscale self-assembly of PNIPAm based copolymers in water near the lower critical solution temperature. 

Conformal Ultrathin Film MOF Analogs: Characterization of Growth Porosity, and Electronic Transport

Lau, J.; Trojniak, A. E.; Maraugha, M. J.; VanZanten, A. J.; Osterbaan, A. J.; Serino, A. C.; Ohnsorg, M. L.; Cheung, K. M.; Ashby, D. S.; Weiss, P. S.; Dunn, B. S.; Anderson, M. E.

Chemistry of Materials, 2019, doi: https://doi.org/10.1021/acs.chemmater.9b03141 

Thin-film formation and transport properties of two copper-paddlewheel metal–organic framework (MOF)-based systems (MOF-14 and MOF-399) are investigated for their potential integration into electrochemical device architectures. The layer-by-layer deposition of these systems provides a promising route to incorporate MOFs as thin films with nanoscale thickness control and low surface roughness for electrochemical devices. 

Comparison of Surface-Bound and Free-Standing Variations of HKUST-1 MOFs: Effect of Activation and Ammonia Exposure on Morphology

Bowser, B. H.; Brower, L. J.; Ohnsorg, M. L.; Gentry, L.; Anderson, M. E.

Nanomaterials, 2018, doi: https://doi.org/10.3390/nano8090650 

Metal-organic frameworks (MOFs) are extremely porous, crystalline materials with high surface area for potential use in gas storage, sequestration, and separations. Toward incorporation into structures for these applications, this study compares three variations of surface-bound and free-standing HKUST-1 MOF structures: surface-anchored MOF (surMOF) thin film, drop-cast film, and bulk powder. Herein, effects of HKUST-1 ammonia interaction and framework activation, which is removal of guest molecules via heat, are investigated.  

Fundamentals of MOF Thin Film Growth via Liquid-Phase Epitaxy: Investigating the Initiation of Deposition and the Influence of Temperature

Ohnsorg, M. L.; Beaudoin, C. K.; Anderson, M. E.

Langmuir, 2015, doi: https://doi.org/10.1021/acs.langmuir.5b01333 

For fabrication of smart interfaces containing surface-anchored metal–organic frameworks, it is important to understand how the foundational layers form to create the interface between the underlying substrate and porous framework. Herein, the formation and morphology of the first ten cycles of film deposition are investigated for the well-studied HKUST-1 system. Effects of processing variables, such as deposition temperature and substrate quality, are studied.  

Metal-Organic Coordinated multilayer Film Formation: Quantitative Analysis of Composition and Structure

Beanson, A. S.; Elinski, M. B.; Ohnsorg, M. L.; Beaudoin, C. K.; Alexander, K. A.; Peaslee, G. F.; DeYoung, P. A; Anderson, M. E.

Thin Solid Films, 2015, doi: https://doi.org/10.1016/j.tsf.2015.07.048 

Metal–organic coordinated multilayers are self-assembled thin films fabricated by alternating solution–phase deposition of bifunctional organic molecules and metal ions. The multilayer film composed of α,ω-mercaptoalkanoic acid and Cu (II) has been the focus of fundamental and applied research with its robust reproducibility and seemingly simple hierarchical architecture. However, internal structure and composition have not been unambiguously established. The composition of films up to thirty layers thick was investigated using Rutherford backscattering spectrometry and particle induced X-ray emission.