Richey Davis
· Professor of Chemical EngineeringVerifiedVirginia Tech · Chemical Engineering
Active 1981–2026
About
Richey Davis is a professor in the Department of Chemical Engineering at Virginia Tech. He holds a Ph.D. from Princeton University, obtained in 1983, and a B.S. from Clemson University, earned in 1977. His research interests include the physical chemistry of polymer solutions, ion-containing polymers, and polymer absorption at interfaces and self-assembly. He is involved in the synthesis, characterization, and applications of polymer nanoparticles, micellar solutions, metal oxide, and metal nanoparticles. His work also encompasses magnetite nanoparticles for magnetic resonance imaging contrast agents and drug-containing nanoparticles for drug delivery, as well as the stability and rheology of colloidal suspensions.
Research topics
- Chemistry
- Materials science
- Biology
- Nanotechnology
- Biophysics
- Biochemistry
- Chemical engineering
- Organic chemistry
- Pharmacology
- Molecular biology
- Cell biology
- Genetics
Selected publications
Ultrasound in Medicine & Biology · 2026-03-06
articleFigshare · 2024-08-27
articleOpen accessGiven the superior soft tissue contrasts obtained by MRI and the long residence times of magnetic nanoparticles (MNPs) in soft tissues, MNP-based theranostic systems are being developed for simultaneous imaging and treatment. However, development of such theranostic nanoformulations presents significant challenges of balancing the therapeutic and diagnostic functionalities in order to achieve optimum effect from both. Here we developed a simple theranostic nanoformulation based on magnetic nanoclusters (MNCs) stabilized by a bisphosphonate-modified poly(glutamic acid)-b-(ethylene glycol) block copolymer and complexed with cisplatin. The MNCs were decorated with luteinizing hormone releasing hormone (LHRH) to target LHRH receptors (LHRHr) overexpressed in ovarian cancer cells. The targeted MNCs significantly improved the uptake of the drug in cancer cells and decreased its IC50 compared to the nontargeted formulations. Also, the enhanced LHRHr-mediated uptake of the targeted MNCs resulted in enhancement in the T2-weighted negative contrast in cellular phantom gels. Taken together, the LHRH-conjugated MNCs show good potential as ovarian cancer theranostics.
Ultrasound in Medicine & Biology · 2023-09-18 · 1 citations
articleOpen accessPharmaceutics · 2023 · 10 citations
Senior authorCorresponding- Chemical engineering
- Chemistry
- Nanotechnology
Flash nanoprecipitation (FNP) is a turbulent mixing process capable of reproducibly producing polymer nanoparticles loaded with active pharmaceutical ingredients (APIs). The nanoparticles produced with this method consist of a hydrophobic core surrounded by a hydrophilic corona. FNP produces nanoparticles with very high loading levels of nonionic hydrophobic APIs. However, hydrophobic compounds with ionizable groups are not as efficiently incorporated. To overcome this, ion pairing agents (IPs) can be incorporated into the FNP formulation to produce highly hydrophobic drug salts that efficiently precipitate during mixing. We demonstrate the encapsulation of the PI3K inhibitor, LY294002, within poly(ethylene glycol)-b-poly(D,L lactic acid) nanoparticles. We investigated how incorporating two hydrophobic IPs (palmitic acid (PA) and hexadecylphosphonic acid (HDPA)) during the FNP process affected the LY294002 loading and size of the resulting nanoparticles. The effect of organic solvent choice on the synthesis process was also examined. While the presence of either hydrophobic IP effectively increased the encapsulation of LY294002 during FNP, HDPA resulted in well-defined colloidally stable particles, while the PA resulted in ill-defined aggregates. The incorporation of hydrophobic IPs with FNP opens the door for the intravenous administration of APIs that were previously deemed unusable due to their hydrophobic nature.
Iron‐based coupling media for MRI‐guided ultrasound surgery
Medical Physics · 2022-09-26 · 4 citations
articleOpen accessPURPOSE: In this study, we examine the effects of a recently developed, iron-based coupling medium (IBCM) on guidance magnetic resonance (MR) scans during transcranial, magnetic-resonance-guided, focused ultrasound surgery (tMRgFUS) procedures. More specifically, this study tests the hypotheses that the use of the IBCM will (a) not adversely affect image quality, (b) remove aliasing from small field-of-view scans, and (c) decouple image quality from the motion state of the coupling fluid. METHODS: An IBCM, whose chemical synthesis and characterization are reported elsewhere, was used as a coupling medium during tMRgFUS procedures on gel phantoms. Guidance magnetization-prepared rapid-gradient-echo (MP-RAGE), TSE, and GRE scans were acquired with fields of view of 28 and 18 cm. Experiments were repeated with the IBCM in several distinct flow states. GRE scans were used to estimate temperature time courses as a gel target was insonated. IBCM performance was measured by computing (i) the root mean square difference (RMSD) of TSE and GRE pixel values acquired using water and the IBCM, relative to the use of water; (ii) through-time temperature uncertainty for GRE scans; and (iii) Bland-Altman analysis of the temperature time courses. Finally, guidance TSE and GRE scans of a human volunteer were acquired during a separate sham tMRgFUS procedure. As a control, all experiments were repeated using a water coupling medium. RESULTS: Use of the IBCM reduced RMSD in TSE scans by a factor of 4 or more for all fields of view and nonstationary motion states, but did not reduce RMSD estimates in MP-RAGE scans. With the coupling media in a stationary state, the IBCM altered estimates of temperature uncertainty relative to the use of water by less than 0.2°C. However, with a high flow state, the IBCM reduced temperature uncertainties by the statistically significant amounts (at the 0.01 level) of 0.5°C (28 cm field of view) and 5°C (18 cm field of view). Bland-Altman analyses found a 0.1°C ± 0.5°C difference between temperature estimates acquired using water and the IBCM as coupling media. Finally, scans of a human volunteer using the IBCM indicate more conspicuous grey/white matter contrast, a reduction in aliasing, and a less than 0.2°C change in temperature uncertainty. CONCLUSIONS: The use of an IBCM during tMRgFUS procedures does not adversely affect image quality for TSE and GRE scans, can decouple image quality from the motion state of the coupling fluid, and can remove aliasing from scans where the field of view is set to be much smaller than the spatial extent of the coupling fluid.
Iron-Based Coupling Medium: Comprehensive Report to FUS Foundation
2021-05-21 · 1 citations
preprintOpen accessThis report gives comprehensive review of the nano-emulsion project between UVA and Virginia Tech which has been generously supported by the Focused Ultrasound Foundation. The purpose of this project is to develop an acoustic coupling bath that is effectively invisible to MRI scans and also remains acoustically compatible with clinical transcranial FUS procedures. This remains important to the clinical translation of FUS because the commonly used acoustic coupling bath of degassed water persistently degrades the quality of MR guidance imaging. Our project proposes an acoustic coupling bath doped with specially designed iron oxide nanoparticles that 1) have a high ability to decay MRI signals, (as quantified by the r2 relaxivity), 2) have diameters less than 100 nm, and 3) are coated with a hydrophilic coating. We hypothesize that these three innovations will produce a lightly doped water bath with identical mechanical, acoustic, thermal, biocompatibility, and electromagnetic properties as water, but with virtually no observable appearance or effect on guidance MR imaging. Finally, the low particle concentrations, small particle sizes, and specific coating will prevent the particles from stabilizing gas bubbles and seeding cavitation nuclei in the transducer’s pre-focal field.We are pleased to report nearly total success on this project, with an affirmation of all hypotheses stated above.
Chemistry of Materials · 2021-09-08
erratumOpen access[This corrects the article PMC10317193.].
2021-10-25
preprintOpen accessBacteria-mediated drug delivery systems comprising nanotherapeutics conjugated onto bacteria synergistically augment the efficacy of both therapeutic modalities in cancer therapy. Nanocarriers preserve therapeutics’ bioavailability and reduce systemic toxicity, while bacteria selectively colonize the cancerous tissue, impart intrinsic and immune-mediated antitumor effects, and propel nanotherapeutics interstitially. The optimal bacteria-nanoparticle (NP) conjugates would carry the maximal NP load with minimal motility speed hindrance for effective interstitial distribution. Furthermore, a well-defined and repeatable NP attachment density distribution is crucial to determining these biohybrid systems’ efficacious dosage and robust performance. Herein, we utilized our Nanoscale Bacteria-Enabled Autonomous Delivery System (NanoBEADS) platform to investigate the effects of assembly process parameters of mixing method, volume, and duration on NP attachment density and repeatability. We also evaluated the effect of linkage chemistry and NP size on NP attachment density, viability, growth rate, and motility of NanoBEADS. We show that the linkage chemistry impacts NP attachment density while the self-assembly process parameters affect the repeatability and, to a lesser extent, attachment density. Lastly, the attachment density affects NanoBEADS’ growth rate and motility in an NP size-dependent manner. These findings will contribute to the development of scalable and repeatable bacteria-nanoparticle biohybrids for applications in drug delivery and beyond. Corresponding author(s) Email: behkam@vt.edu
2021-09-07
preprintOpen accessBacteria-mediated drug delivery systems comprising nanotherapeutics conjugated onto bacteria synergistically augment the efficacy of both therapeutic modalities in cancer therapy. Nanocarriers preserve therapeutics’ bioavailability and reduce systemic toxicity, while bacteria selectively colonize the cancerous tissue, impart intrinsic and immune-mediated antitumor effects, and propel nanotherapeutics interstitially. The optimal bacteria-nanoparticle (NP) conjugates would carry the maximal NP load with minimal motility speed hindrance for effective interstitial distribution. Furthermore, a well-defined and repeatable NP attachment density distribution is crucial to determining these biohybrid systems’ efficacious dosage and robust performance. Herein, we utilized our Nanoscale Bacteria-Enabled Autonomous Delivery System (NanoBEADS) platform to investigate the effects of assembly process parameters of mixing method, volume, and duration on NP attachment density and repeatability. We also evaluated the effect of linkage chemistry and NP size on NP attachment density, viability, growth rate, and motility of NanoBEADS. We show that the linkage chemistry impacts NP attachment density while the self-assembly process parameters affect the repeatability and, to a lesser extent, attachment density. Lastly, the attachment density affects NanoBEADS’ growth rate and motility in an NP size-dependent manner. These findings will contribute to the development of scalable and repeatable bacteria-nanoparticle biohybrids for applications in drug delivery and beyond. Corresponding author(s) Email: behkam@vt.edu
2021-10-11
preprintBacteria-mediated drug delivery systems comprising nanotherapeutics conjugated onto bacteria synergistically augment the efficacy of both therapeutic modalities in cancer therapy. Nanocarriers preserve therapeutics’ bioavailability and reduce systemic toxicity, while bacteria selectively colonize the cancerous tissue, impart intrinsic and immune-mediated antitumor effects, and propel nanotherapeutics interstitially. The optimal bacteria-nanoparticle (NP) conjugates would carry the maximal NP load with minimal motility speed hindrance for effective interstitial distribution. Furthermore, a well-defined and repeatable NP attachment density distribution is crucial to determining these biohybrid systems’ efficacious dosage and robust performance. Herein, we utilized our Nanoscale Bacteria-Enabled Autonomous Delivery System (NanoBEADS) platform to investigate the effects of assembly process parameters of mixing method, volume, and duration on NP attachment density and repeatability. We also evaluated the effect of linkage chemistry and NP size on NP attachment density, viability, growth rate, and motility of NanoBEADS. We show that the linkage chemistry impacts NP attachment density while the self-assembly process parameters affect the repeatability and, to a lesser extent, attachment density. Lastly, the attachment density affects NanoBEADS’ growth rate and motility in an NP size-dependent manner. These findings will contribute to the development of scalable and repeatable bacteria-nanoparticle biohybrids for applications in drug delivery and beyond. Corresponding author(s) Email: behkam@vt.edu
Frequent coauthors
- 87 shared
Judy S. Riffle
Virginia Tech
- 39 shared
N. S. Broyles
Freeport-McMoRan (United States)
- 37 shared
John J. Lesko
Virginia Tech
- 35 shared
K.N.E. Verghese
- 28 shared
James R. Heflin
- 23 shared
Nikorn Pothayee
- 19 shared
Harry W. Gibson
Amsterdam University Medical Centers
- 16 shared
Charles Brands
Education
- 1983
PhD, Chemical Engineering
Princeton University
- 1977
BS, Chemical Engineering
Clemson University
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