Is standardization the key to unlocking the potential of nanomedicine?
Systems Biology Laboratory, School of Mathematics and Statistics, Department of Biomedical Engineering, and ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, University of Melbourne, Parkville, Victoria 3010, Australia
Nanoengineering therapeutics to have specific functionalities – such as avoidance of the immune system or preferential uptake by diseased cells – is a major goal of many researchers within the Controlled Release Society. Identification and development of “nanomedicines” starts with pre-clinical, fundamental evaluation of nanomaterials – an area sometimes labeled “bio-nano interactions”. This phase of research spans material synthesis and characterization, in vitro cell culturing studies, and in vivo animal studies. Thus, it brings together researchers from a wide variety of backgrounds, including materials science, chemistry, biology, engineering, and computational sciences. I work as part of the Australian Research Council’s Centre of Excellence in Convergent Bio-Nano Science and Technology (CBNS, http://www.cbns.org), whose research focus is “to understand the bio-nano interface to better predict, control and visualize the myriad interactions that occur between nanomaterials and the biological environment.” Over time, we have become increasingly convinced that a lack of standardization has been holding back progress and understanding in this area.
Many research fields, as they mature, gravitate towards more formal expectations for experiments, results, and work that is performed. However, this evolution towards standardization has been slow in the field of bio-nano interactions. Plausible explanations for why include its large size, its highly multidisciplinary nature, or the dizzying pace of publication in this domain. Regardless of the reason, I – and my colleagues in the CBNS – believe the time has come to make changes. The lack of attention to standardization may be an under-appreciated contributor to concerns about reproducibility,1 perceived poor performance and translation of targeted therapeutics,2 and high-profile commercial failures.
Standardization can take many forms. We have recently proposed a reporting standard, MIRIBEL (“Minimum Information Reporting in Bio-nano Experimental Literature”), designed to set cross-field expectations for the material and biological characterization that is reported, as well as the details of experimental protocol used to conduct this characterization.3 Not every component is relevant for every investigation (for instance, some are specific to cell culture experiments); but all are worth consideration. We advocate considering the components of MIRIBEL both when planning a new investigation, as well as during manuscript preparation. To aid this, MIRIBEL contains a supplementary “checklist” of each component (https://osf.io/smvtf/). Use of this checklist (and its inclusion in publications) has an additional benefit: it allows readers of your work to quickly determine what information is contained within, aiding meta-analysis and reuse of your published data. MIRIBEL can also serve as a “template” to train and guide students and researchers new to the domain of bio-nano interactions.
However, MIRIBEL is just one step on a path towards improving research through standardization. Undoubtedly, it will need to be amended by the community and as our understanding of the bio-nano interface improves. And the community must come to a consensus not only about which properties are important, but how to determine them and where to store them (e.g., in central databases and institutional repositories). I am encouraged by recent work proposing additional domain-specific standardization and improvements to reporting,4–6 and hope that these efforts continue.
Quantitative bio-nano interactions in vitro
Metrics – which simplify complex data into quantitative, comparable results – are also an important step of standardization during the maturation of a field. Metrics facilitate comparison and evaluation of published research. For instance, in vivo studies nearly always use pharmacokinetic and pharmacodynamic models to derive parameters such as circulation half-life, or clearance rate into a particular organ. These parameters enable comparison of experiments done under different conditions or assessed with different instruments.
In contrast to PK/PD for in vivo work, there are few established metrics for comparing in vitro results in the domain of drug delivery. However, this does not have to be the case. We have recently developed a methodology for direct, quantitative comparison of in vitro cellular association assays done under different conditions, with different particles, and/or with different types of cell.7 This method turns cellular association assays (which are ubiquitous in early stage evaluation of targeted or stealth materials) from a qualitative result to a quantitative one (Fig. 1).
How is this accomplished? The core of this approach is a mathematical model which treats the interaction between cells and nanoengineered particles as a reaction on a surface, as well as accounting for the movement of material in solution prior to contact with the cells. By fitting experimental data to our mathematical model, we can determine a “missing” kinetic parameter which describes the interaction strength between a pairing of cell line and particle. This kinetic parameter or “affinity” can thus serve as a quantitative metric of the stealth or targeting performance between a cell line and a particle, and can be used to compare disparate experiments. For any who are interested in applying this quantitative approach to their own data, we also have a companion website (http://bionano.xyz/estimator) - no programming, mathematics, or downloads required. Ultimately, I envision that quantitative in vitro screening against panels of cells which represent both the target and the immune system will become common, leading to better prediction of in vivo performance.
Standardization means nothing without broader community engagement and uptake, and there is still much work left to do in this area. The next step is further community discussion, amendment, and (hopefully) uptake of common standards. Journals can also play a critical role in this process by formalizing community standards through author guidelines, instructions to reviewers, and/or requirements for manuscript submission. If you are interested in or want to be part of the work presented above, please get in touch!
Above all, we must not lose sight of the goal of finding ways to translate and generalize results from one phase of research to the next (e.g., from cell culture experiments to animal studies). This is no easy task, and only together can we can unlock the potential of targeted and controlled delivery of therapeutics.
(1) Leroux, J.-C. Editorial: Drug Delivery: Too Much Complexity, Not Enough Reproducibility? Angew. Chemie Int. Ed. 2017, 56, 15170–15171.
(2) Park, K. The Drug Delivery Field at the Inflection Point: Time to Fight Its Way out of the Egg. J. Control. Release 2017, 267, 2–14.
(3) Faria, M.; Björnmalm, M.; Thurecht, K. J.; Kent, S. J.; Parton, R. G.; Kavallaris, M.; Johnston, A. P. R.; Gooding, J. J.; Corrie, S. R.; Boyd, B. J.; Thordarson, P.; Whittaker, A. K.; Stevens, M. M.; Prestidge, C. A.; Porter, C. J. H.; Parak, W. J.; Davis, T. P.; Crampin, E. J.; Caruso, F. Minimum Information Reporting in Bio–Nano Experimental Literature. Nat. Nanotechnol. 2018, 13, 777–785.
(4) Millstone, J. E.; Chan, W. C. W.; Kagan, C. R.; Liz-Marzán, L. M.; Kotov, N. A.; Mulvaney, P. A.; Parak, W. J.; Rogach, A. L.; Weiss, P. S.; Schaak, R. E. Redefining the Experimental and Methods Sections. ACS Nano 2019, 13, 4862–4864.
(5) Théry, C.; Witwer, K. W.; Aikawa, E.; Alcaraz, M. J.; Anderson, J. D.; Andriantsitohaina, R.; Antoniou, A.; Arab, T.; Archer, F.; Atkin-Smith, G. K.; Ayre, D. C.; Bach, J. M.; Bachurski, D.; Baharvand, H.; Balaj, L.; Baldacchino, S.; Bauer, N. N.; Baxter, A. A.; Bebawy, M.; et al. Minimal Information for Studies of Extracellular Vesicles 2018 (MISEV2018): A Position Statement of the International Society for Extracellular Vesicles and Update of the MISEV2014 Guidelines. J. Extracell. Vesicles 2018, 7.
(6) Nicolas, J.; Liu, S.; Zhao, D.; Caruso, F.; Reichmanis, E.; Buriak, J. M. Best Practices for New Polymers and Nanoparticulate Systems. Chem. Mater. 2018, 30, 6587–6588.
(7) Faria, M.; Noi, K. F.; Dai, Q.; Björnmalm, M.; Johnston, S. T.; Kempe, K.; Caruso, F.; Crampin, E. J. Revisiting Cell–Particle Association in Vitro: A Quantitative Method to Compare Particle Performance. J. Control. Release 2019.