About

Keith Johnston is the Cockrell Family Dean's Chair in Engineering Excellence at the University of Texas at Austin's McKetta Department of Chemical Engineering. His research focuses on combining materials chemistry, colloid and interface science, and polymer science to develop applications across various fields, including drug delivery, biomedical imaging and therapy, electrocatalysis in energy storage, and subsurface energy production. He has discovered or co-discovered various nanomaterials such as water/CO2 microemulsions, silicon nanowires, and highly active perovskite electrocatalysts and supercapacitors. Johnston has made significant contributions to nanotechnology for subsurface green energy production, which encompasses CO2 sequestration, improved oil recovery, magnetic nanomaterials for electromagnetic imaging of reservoirs, nanocapsule delivery, and greener fracturing with low water utilization. His work integrates materials chemistry, colloid and interface science, and polymer science to guide the development of innovative solutions in these areas. He holds a Ph.D. from the University of Illinois (1981) and a B.S. from the University of Michigan (1977). Johnston has received numerous awards and honors, including being named a fellow of the American Institute of Medical and Biological Engineers in 2013, election to the National Academy of Engineering in 2011, and recognition as one of the '100 Chemical Engineers of the Modern Era' by the American Institute of Chemical Engineers in 2008.

Research topics

• Materials science
• Chemistry
• Environmental engineering
• Polymer chemistry
• Chemical engineering
• Environmental science
• Process engineering
• Organic chemistry
• Nanotechnology
• Composite material
• Oceanography
• Medicine
• Meteorology
• Surgery
• Waste management
• Geology
• Pulp and paper industry
• Engineering

Selected publications

• Rapid Screening Method to Assess Formation Damage During Injection of Metal Oxide Nanoparticles in Sandstone

  Nanomaterials · 2026-03-26

  articleOpen access

  Many advances in enhanced oil recovery (EOR) take advantage of the unique properties of nanomaterials to improve characterization of formation properties, achieve conformance control during flood operations, and extend the controlled release time of polymers. Magnetite nanoparticles (nMag) have been employed in these processes due to their low cost, low toxicity, and ability to be engineered to meet desired needs, especially with the application of a magnetic field. Similarly, silica dioxide (SiO2) and aluminum oxide (Al2O3) nanoparticles have been evaluated for the delivery of scale and asphaltene inhibitors. However, the injection of nanoparticles into porous media comes with the risk of formation damage due to particle deposition, which can lead to increased injection pressures and reductions in permeability. The goal of this study was to develop a method to evaluate and assess nanoparticle formulations for their potential to cause formation damage. A screening apparatus was constructed to hold small sandstone discs (~2 mm) or cores (~2.5 cm) for rapid testing with minimal material use and the capability to be used with either aqueous brine solutions or non-polar solvents as the mobile phase. Image analysis of the disc and pressure measurements demonstrated increasing deposition of nMag and face-caking when the salinity was increased from 500 mg/L NaCl (8.56 mM) to API brine (2.0 M). Similarly, when the injected concentration of silica nanoparticles in 500 mg/L NaCl was increased from 1 to 10 wt%, the back pressure increased by 55 psi, and face-caking was observed. The screening test results were consistent with traditional core-flood tests and was able to be modified to accommodate organic liquid mobile phases. The screening test results closely matched nanoparticle transport and retention measured in sandstone cores, confirming the ability of the system to rapidly screen nanoparticle formulations for potential formation damage.

  PublisherOA PDFDOI

• Structural heterogeneity in mRNA-LNP subpopulations revealed by AF4-SAXS: implications for cargo loading and cell transfection

  bioRxiv (Cold Spring Harbor Laboratory) · 2026-01-17

  articleOpen access

  Lipid nanoparticles are the leading platform for the delivery of nucleic acid therapeutics, yet their structural complexity remains a significant barrier to achieve rational design and predictable function. Part of this complexity arises from the non-equilibrium assemblies that are difficult to identify using ensemble average techniques given the substantial heterogeneity in all properties. Aiming to overcome the limitations of traditional characterization methods, we combined asymmetric flow field-flow fractionation with in-line small-angle X-ray scattering and spectroscopic analyses, nanoflow cytometry, and cryo-EM to construct detailed structural models of mRNA-loaded nanoparticles formulated with different amounts of mRNA loading (N/P ratios of 3 and 6). This combination of techniques revealed that microfluidic formulation produces structurally diverse nanoparticle subpopulations differing in size, anisotropy, and cargo loading. Notably, these variations extend to the particle internal organization: spheroidal geometries display densely loaded mRNA cores, whereas bleb-like morphologies exhibit reduced mRNA content relative to the lipid amount within segregated domains at the core. NanoFCM further shows that the N/P ratio modulates cargo distribution across individual nanoparticles, with N/P=6 yielding a more uniform mRNA copy number per particle across subpopulations than N/P=3. These differences resulted in higher transfection efficacies for the N/P=6 formulation, highlighting core organization and loading homogeneity as key parameters for efficacious delivery. Together, these results establish a direct link between LNP architecture, internal organization, cargo distribution, and transfection efficiency, underscoring the importance of accounting for heterogeneity in the rational design of nucleic acid delivery systems.

  PublisherOA PDFDOI

• Targeted, polymersome-encapsulated indocyanine green J-aggregates for clinically translatable molecular photoacoustic imaging (Conference Presentation)

  2025-03-20

  article
  PublisherDOI

• Directional conjugation of monoclonal antibodies to nanoparticles using metal-free click chemistry

  Nature Protocols · 2025-11-19 · 1 citations

  article
  PublisherDOI

• Viscosity of concentrated antibodies from a dynamic model of electrostatics

  Proceedings of the National Academy of Sciences · 2025-11-17 · 1 citations

  articleOpen access1st authorCorresponding
  PublisherDOI

• Ultra Long-Term Release of Oligomeric Surfactants from Mesoporous Silica Nanoparticles into Organic Solvents

  SSRN Electronic Journal · 2025-01-01

  preprintOpen accessSenior author
  PublisherDOI

• Ultra long-term release of oligomeric surfactants from mesoporous silica nanoparticles into organic solvents

  Colloids and Surfaces A Physicochemical and Engineering Aspects · 2025-10-12

  articleSenior authorCorresponding
  PublisherDOI

• Growth of Clusters toward Liquid–Liquid Phase Separation of Monoclonal Antibodies as Characterized by Small-Angle X-ray Scattering and Molecular Dynamics Simulation

  The Journal of Physical Chemistry B · 2025-03-07 · 5 citations

  articleOpen accessSenior authorCorresponding

  In concentrated protein solutions, short-range attractions (SRAs) contribute to liquid–liquid phase separation (LLPS) as a function of temperature and salinity, particularly when the charge and thus long-range repulsions are low near the isoelectric point pI. Herein, we study how SRA and solution morphology vary with the approach to LLPS from increased SRA for two monoclonal antibodies (mAbs) as salt concentration is reduced near the pI. These properties are quantified using small-angle X-ray scattering (SAXS) interpreted via coarse-grained (CG) molecular dynamics (MD) simulations and compared with less descriptive properties from static and dynamic light scattering. Experimental structure factors are fit with a library of MD simulations for a CG 12-bead mAb model to determine the SRA strength (K) and cluster size distributions. Proximity to LLPS and clustering characteristics in mAb solutions are impacted by both net charge, which are modified by pH, and the strength of anisotropic electrostatic SRA (charge–charge, charge–dipole, hydrogen bonding, etc.), which are screened and weakened by added salts. The trends in LLPS are consistent with the reduced diffusion interaction parameter kD/B22ex for dilute solutions. However, greater insight is provided with SAXS along with CG-MD simulations; in particular, the growth of clusters is observed with the approach to LLPS with decreasing salinity over a wide range of concentrations.

  PublisherOA PDFDOI

• Antibody-Conjugated Polymersomes with Encapsulated Indocyanine Green J-Aggregates and High Near-Infrared Absorption for Molecular Photoacoustic Cancer Imaging

  ACS Applied Materials & Interfaces · 2024-01-25 · 20 citations

  articleOpen accessSenior authorCorresponding

  Imaging plays a critical role in all stages of cancer care from early detection to diagnosis, prognosis, and therapy monitoring. Recently, photoacoustic imaging (PAI) has started to emerge into the clinical realm due to its high sensitivity and ability to penetrate tissues up to several centimeters deep. Herein, we encapsulated indocyanine green J (ICGJ) aggregate, one of the only FDA-approved organic exogenous contrast agents that absorbs in the near-infrared range, at high loadings up to ∼40% w/w within biodegradable polymersomes (ICGJ-Ps) composed of poly(lactide-co-glycolide-b-polyethylene glycol) (PLGA-b-PEG). The small Ps hydrodynamic diameter of 80 nm is advantageous for in vivo applications, while directional conjugation with epidermal growth factor receptor (EGFR) targeting cetuximab antibodies renders molecular specificity. Even when exposed to serum, the ∼11 nm-thick membrane of the Ps prevents dissociation of the encapsulated ICGJ for at least 48 h with a high ratio of ICGJ to monomeric ICG absorbances (i.e., I895/I780 ratio) of approximately 5.0 that enables generation of a strong NIR photoacoustic (PA) signal. The PA signal of polymersome-labeled breast cancer cells is proportional to the level of cellular EGFR expression, indicating the feasibility of molecular PAI with antibody-conjugated ICGJ-Ps. Furthermore, the labeled cells were successfully detected with PAI in highly turbid tissue-mimicking phantoms up to a depth of 5 mm with the PA signal proportional to the amount of cells. These data show the potential of molecular PAI with ICGJ-Ps for clinical applications such as tumor margin detection, evaluation of lymph nodes for the presence of micrometastasis, and laparoscopic imaging procedures.

  PublisherOA PDFDOI

• Covalently Cross-Linked Polyelectrolyte Complex Nanoparticles with Enhanced Stability against Dissociation at High Ionic Strength

  Langmuir · 2024-12-23 · 1 citations

  articleSenior authorCorresponding

  Polyelectrolyte complex nanoparticles (PECNPs) often fully dissociate into individual polycations (PC) and polyanions (PA) at high salinities. Herein, we introduce a novel type of colloidally stable PECNP in which the PC is cross-linked, in this case branched polyethylenimine (PEI) to limit this dissociation, even in solutions up to 5.2 M NaCl or 5.4 M CaCl2. For cross-linked PECNPs at specified conditions, the size and the PC (poly(vinylsulfonate)) partition coefficient reach equilibrium within the first 24 h and change very little for 7 weeks. From the determination of the released polyanion concentration over a wide range in PEI protonation degree (f), it was found that strong nonelectrostatic (hydrophobic) as well as electrostatic interactions between the PC and PA control the degree of dissociation. The electrostatic repulsion from the PEI chains on the surface provided long-term colloidal stability with PECNP hydrodynamic diameters on the order of 200 to 300 nm. The ability to achieve partial dissociation of a PECNP up to ultrahigh salinity creates new opportunities in fundamental experimental and theoretical studies of PECNP with relevance to controlled release in subsurface energy and environmental applications.

  PublisherDOI

Recent grants

• Colloidal Assembly of Biodegradable Multifunctional Nanoclusters

  NSF · $335k · 2010–2014

Frequent coauthors

• Robert O. Williams

  Austin College

  66 shared

• Konstantin Sokolov

  The University of Texas MD Anderson Cancer Center

  52 shared

• Thomas M. Truskett

  48 shared

• Kwon Taek Lim

  Pukyong National University

  46 shared

• Chun Huh

  43 shared

• Steven L. Bryant

  University of Calgary

  39 shared

• Peter F. Green

  Oak Ridge National Laboratory

  38 shared

• Keith J. Stevenson

  Lomonosov Moscow State University

  38 shared

Education

• Ph.D.

  University of Illinois

  1981

• B.S.

  University of Michigan

  1977

Awards & honors

• American Institute of Medical and Biological Engineers fello…
• National Academy of Engineering (2011)
• Named one of “the 100 Chemical Engineers of the Modern Era”…
• Institute Award for Excellence in Industrial Gases Technolog…
• Technological Innovation Finalist – Discover Magazine Awards…