About

Ronald A. Siegel, ScD, is a Professor and Director of Graduate Studies in the Department of Pharmaceutics at the University of Minnesota. He received his ScD degree in Electrical Engineering and Computer Science from the Massachusetts Institute of Technology (MIT) in 1984. His academic career includes faculty positions at the University of California, San Francisco, where he was on the faculty of the School of Pharmacy from 1984 to 1998, before moving to the University of Minnesota in 1998. He served as Head of the Department of Pharmaceutics from 1999 to 2009 and again from 2022 to 2024, and is also part of the faculty of the Department of Biomedical Engineering. His research interests encompass intranasal prodrugs and delivery systems for the treatment of epilepsy, hydrogels and polymer-drug interactions, development of inert biodegradable polymers for implants, and physical and mathematical modeling of processes governing drug disposition. Dr. Siegel's work involves polymer synthesis and characterization, UV-Vis, NMR, FTIR, DSC, DTA, PXRD, HPLC, and mathematical and computational modeling. His academic focus includes controlled drug and gene delivery, physical chemistry, and physical pharmacy, with courses taught in these areas.

Research topics

• Materials science
• Composite material
• Chemical engineering
• Organic chemistry
• Chemistry
• Biomedical engineering
• Nanotechnology
• Polymer chemistry
• Chromatography

Selected publications

• Probing Miscibility of Spray-Dried and Melt-Quenched Amorphous Dispersions Using Rheology and Solid-State NMR Spectroscopy

  Molecular Pharmaceutics · 2026-01-24 · 1 citations

  articleSenior authorCorresponding

  A c*-guided high-temperature rheological approach and solid-state NMR (ssNMR) 1H T1ρ and 1H T1 relaxation time measurements were used to estimate the miscibility of celecoxib (CEL)/polyvinylpyrrolidone (PVP) amorphous solid dispersions (ASDs) prepared by melt quench and spray drying. The ssNMR spin diffusion method is capable of investigating the miscibility of ASDs processed by the two methods, as it measures as-is ASD powders, while the c*-guided high-temperature rheological approach cannot, since it erases the processing history. Our results indicate a general agreement of the estimated miscibility of ASDs prepared by the two processing methods. The crystallization tendency is significantly different when the polymer concentration c is below and above c*. When c < c*, the onset of crystallization in dilute CEL/PVP ASDs is approximately identical to that of neat amorphous CEL. However, when c > c*, the first evidence of CEL crystallization is significantly delayed, indicating a reduced crystallization propensity. These results confirm that the efficient and material-sparing rheological approach can be used to estimate the miscibility (limit) and predict stability against crystallization for both melt-extruded and spray-dried ASDs. Our findings are useful in the rational and efficient design of robust ASDs with a desirable stability against crystallization during long-term storage.

  PublisherDOI

• Artificial gut Simulator. A scheme to predict intestinal and plasma concentration–time profiles of a weakly basic BCS-II drug, dipyridamole

  European Journal of Pharmaceutics and Biopharmaceutics · 2025-03-13 · 3 citations

  articleSenior authorCorresponding
  PublisherDOI

• Progress towards a prodrug/enzyme intranasal delivery system for rapid prevention/reversal of seizure emergency

  Journal of Controlled Release · 2025-09-22

  article1st authorCorresponding
  PublisherDOI

• Experiments and finite element simulations pertinent to hydrogel debonding from a solid substrate

  Polymer · 2025-07-04 · 4 citations

  articleCorresponding
  PublisherDOI

• Delaying the first nucleation event of amorphous solid dispersions above the polymer overlap concentration (c*): PVP and PVPVA in posaconazole

  Journal of Pharmaceutical Sciences · 2024-04-28 · 10 citations

  articleOpen accessSenior author
  PublisherOA PDFDOI

• A Numerical Scheme and Validation of the Asymptotic Energy Release Rate Formula for a 2D Gel Thin-Film Debonding Problem

  SIAM Journal on Applied Mathematics · 2024-08-13 · 2 citations

  article
  PublisherDOI

• Author response for "Efficient Development of High Drug Loaded Posaconazole Tablets Enabled by Amorphous Solid Dispersion"

  2024-11-21

  peer-review
  PublisherDOI

• An Artificial Gut/Absorption Simulator: Understanding the Impact of Absorption on In Vitro Dissolution, Speciation, and Precipitation of Amorphous Solid Dispersions

  Molecular Pharmaceutics · 2024-03-21 · 4 citations

  articleSenior authorCorresponding

  Upon dissolution, amorphous solid dispersions (ASDs) of poorly water-soluble compounds can generate supersaturated solutions consisting of bound and free drug species that are in dynamic equilibrium with each other. Only free drug is available for absorption. Drug species bound to bile micelles, polymer excipients, and amorphous and crystalline precipitate can reduce the drug solute's activity to permeate, but they can also serve as reservoirs to replenish free drug in solution lost to absorption. However, with multiple processes of dissolution, absorption, and speciation occurring simultaneously, it may become challenging to understand which processes lead to an increase or decrease in drug solution concentration. Closed, nonsink dissolution testing methods used routinely, in the absence of drug removal, allow only for static equilibrium to exist and obscure the impact of each drug species on absorption. An artificial gut simulator (AGS) introduced recently consists of a hollow fiber-based absorption module and allows mass transfer of the drug from the dissolution media at a physiological rate after tuning the operating parameters. In the present work, ASDs of varying drug loadings were prepared with a BCS-II model compound, ketoconazole (KTZ), and hypromellose acetate succinate (HPMCAS) polymer. Simultaneous dissolution and absorption testing of the ASDs was conducted with the AGS, and simple analytical techniques were utilized to elucidate the impact of bound drug species on absorption. In all cases, a lower amount of crystalline precipitate was formed in the presence of absorption relative to the nonsink dissolution "control". However, formation of HPMCAS-bound drug species and crystalline precipitate significantly reduced KTZ absorption. Moreover, at high drug loading, inclusion of an absorption module was shown to enhance ASD dissolution. The rank ordering of the ASDs with respect to dissolution was significantly different when nonsink dissolution versus AGS was used, and this discrepancy could be mechanistically elucidated by understanding drug dissolution and speciation in the presence of absorption.

  PublisherDOI

• Impact of solid content on the bulk properties of lyophilized powders

  International Journal of Pharmaceutics · 2024-12-20 · 6 citations

  article
  PublisherDOI

• Efficient development of high drug loaded posaconazole tablets enabled by amorphous solid dispersion

  RSC Pharmaceutics · 2024-12-04 · 6 citations

  articleOpen accessCorresponding

  A 50% API-loaded posaconazole tablet was developed in 14 days using just 1.5 g of API through systematic evaluation of stability, dissolution, and manufacturability.

  PublisherOA PDFDOI

Recent grants

• NIH Grant R21EB003125

  NIH · $397k · 2006

• NIH Grant R01DK038035

  NIH · $348k · 1991

• Pulsating Polymer Gel

  NSF · $220k · 1997–1999

• NIH Grant R56DK075739

  NIH · $331k · 2010

• NIH Grant R01HD040366

  NIH · $1.0M · 2008

Frequent coauthors

• Babak Ziaie

  Atlantic Technological University

  27 shared

• Sichen Song

  20 shared

• Antonio Baldi

  Institut de Microelectrònica de Barcelona

  19 shared

• Manuel A. Sánchez

  15 shared

• Bruce A. Firestone

  Allergan (United States)

  15 shared

• Duvan Henao

  University of O'Higgins

  14 shared

• Yuandong Gu

  Shanghai University

  14 shared

• Mikhail M. Feldstein

  Lomonosov Moscow State University

  13 shared

Awards & honors

• Fellow, CRS, 2010
• CRS/Jorge Heller Journal of Controlled Release Outstanding P…
• CRS/Ethypharm Best Pharmaceutical Paper Award, 2001
• Fellow, American Association of Pharmaceutical Scientists, 1…
• Fellow, American Institute for Medical and Biological Engine…