Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Shear-thinning and self-healing hydrogels as injectable therapeutics and for 3D-printing

Nature Protocols volume 12, pages 1521–1541 (2017)Cite this article

Subjects

Abstract

The design of injectable hydrogel systems addresses the growing demand for minimally invasive approaches for local and sustained delivery of therapeutics. We developed a class of hyaluronic acid (HA) hydrogels that form through noncovalent guest–host interactions, undergo disassembly (shear-thinning) when injected through a syringe and then reassemble within seconds (self-healing) when shear forces are removed. Its unique properties enable the use of this hydrogel system for numerous applications, such as injection in vivo (including with cells and therapeutic molecules) or as a 'bioink' in 3D-printing applications. Here, we describe the functionalization of HA either with adamantanes (guest moieties) via controlled esterification or with β-cyclodextrins (host moieties) through amidation. We also describe how to modify the HA derivatives with methacrylates for secondary covalent cross-linking and for reaction with fluorophores for in vitro and in vivo imaging. HA polymers are rationally designed from relatively low-molecular-weight starting materials, with the degree of modification controlled, and have matched guest-to-host stoichiometry, allowing the preparation of hydrogels with tailored properties. This procedure takes 3–4 weeks to complete. We detail the preparation and characterization of the guest–host hydrogels, including assessment of their rheological properties, erosion and biomolecule release in vitro. We furthermore demonstrate how to encapsulate cells in vitro and provide procedures for quantitative assessment of in vivo hydrogel degradation by imaging of fluorescently derivatized materials.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Rent or buy this article

Prices vary by article type

from$1.95

to$39.95

Learn more

Prices may be subject to local taxes which are calculated during checkout

Figure 1: Overview of the guest–host hydrogel platform.
Figure 2: Application of GH hydrogels for local delivery of therapeutics.
Figure 3: Application of GH hydrogels as injectable cell carriers.
Figure 4: Direct 3D-bioprinting of GH hydrogels and secondary stabilization for fabrication of complex 3D structures.
Figure 5: Guest and host polymer synthesis schemes.
Figure 6: Guest–host hydrogel preparation and injection.
Figure 7: Guest–host assembly and recovery mechanism.

References

  1. Li, J. & Mooney, D.J. Designing hydrogels for controlled drug delivery. Nat. Rev. Mater. 1, 16071 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  2. Burdick, J.A. & Murphy, W.L. Moving from static to dynamic complexity in hydrogel design. Nat. Commun. 3, 1269 (2012).

    Article  PubMed  CAS  Google Scholar 

  3. Drury, J.L. & Mooney, D.J. Hydrogels for tissue engineering: scaffold design variables and applications. Biomaterials 24, 4337–4351 (2003).

    Article  CAS  PubMed  Google Scholar 

  4. Ifkovits, J.L. & Burdick, J.A. Review: photopolymerizable and degradable biomaterials for tissue engineering applications. Tissue Eng. 13, 2369–2385 (2007).

    Article  CAS  PubMed  Google Scholar 

  5. Nguyen, K.T. & West, J.L. Photopolymerizable hydrogels for tissue engineering applications. Biomaterials 23, 4307–4314 (2002).

    Article  CAS  PubMed  Google Scholar 

  6. Ifkovits, J.L. et al. Injectable hydrogel properties influence infarct expansion and extent of postinfarction left ventricular remodeling in an ovine model. Proc. Natl. Acad. Sci. USA 107, 11507–11512 (2010).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  7. Jin, R. et al. Synthesis and characterization of hyaluronic acid–poly(ethylene glycol) hydrogels via Michael addition: an injectable biomaterial for cartilage repair. Acta Biomater. 6, 1968–1977 (2010).

    Article  CAS  PubMed  Google Scholar 

  8. Lehn, J.-M. Perspectives in supramolecular chemistry—from molecular recognition towards molecular information processing and self-organization. Angew. Chem. Int. Ed. Engl. 29, 1304–1319 (1990).

    Article  Google Scholar 

  9. Tibbitt, M.W., Rodell, C.B., Burdick, J.A. & Anseth, K.S. Progress in material design for biomedical applications. Proc. Natl. Acad. Sci. USA 112, 14444–14451 (2015).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  10. Wang, H. & Heilshorn, S.C. Adaptable hydrogel networks with reversible linkages for tissue engineering. Adv. Mater. 27, 3717–3736 (2015).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  11. Webber, M.J., Appel, E.A., Meijer, E.W. & Langer, R. Supramolecular biomaterials. Nat. Mater. 15, 13–26 (2016).

    Article  CAS  PubMed  Google Scholar 

  12. Guvendiren, M., Lu, H.D. & Burdick, J.A. Shear-thinning hydrogels for biomedical applications. Soft Matter 8, 260–272 (2012).

    Article  CAS  Google Scholar 

  13. DiMarco, R.L. & Heilshorn, S.C. Multifunctional materials through modular protein engineering. Adv. Mater. 24, 3923–3940 (2012).

    Article  CAS  PubMed  Google Scholar 

  14. Lu, H.D., Charati, M.B., Kim, I.L. & Burdick, J.A. Injectable shear-thinning hydrogels engineered with a self-assembling Dock-and-Lock mechanism. Biomaterials 33, 2145–2153 (2012).

    Article  CAS  PubMed  Google Scholar 

  15. Rodell, C.B., Mealy, J.E. & Burdick, J.A. Supramolecular guest-host interactions for the preparation of biomedical materials. Bioconjug. Chem. 26, 2279–2289 (2015).

    Article  CAS  PubMed  Google Scholar 

  16. Yang, X. et al. Self-healing polymer materials constructed by macrocycle-based host-guest interactions. Soft Matter 11, 1242–1252 (2015).

    Article  CAS  PubMed  Google Scholar 

  17. Ma, X. & Zhao, Y. Biomedical applications of supramolecular systems based on host–guest interactions. Chem. Rev. 115, 7794–7839 (2015).

    Article  CAS  PubMed  Google Scholar 

  18. Highley, C.B., Prestwich, G.D. & Burdick, J.A. Recent advances in hyaluronic acid hydrogels for biomedical applications. Curr. Opin. Biotechnol. 40, 35–40 (2016).

    Article  CAS  PubMed  Google Scholar 

  19. Charlot, A. & Auzély-Velty, R. Synthesis of novel supramolecular assemblies based on hyaluronic acid derivatives bearing bivalent β-cyclodextrin and adamantane moieties. Macromolecules 40, 1147–1158 (2007).

    Article  CAS  Google Scholar 

  20. Charlot, A., Auzély-Velty, R. & Rinaudo, M. Specific interactions in model charged polysaccharide systems. J. Phys. Chem. B 107, 8248–8254 (2003).

    Article  CAS  Google Scholar 

  21. Semenov, A., Charlot, A., Auzély-Velty, R. & Rinaudo, M. Rheological properties of binary associating polymers. Rheol. Acta 46, 541–568 (2007).

    Article  CAS  Google Scholar 

  22. Rodell, C.B., Kaminski, A.L. & Burdick, J.A. Rational design of network properties in guest-host assembled and shear-thinning hyaluronic acid hydrogels. Biomacromolecules 14, 4125–4134 (2013).

    Article  CAS  PubMed  Google Scholar 

  23. Gaffey, A.C. et al. Injectable shear-thinning hydrogels used to deliver endothelial progenitor cells, enhance cell engraftment, and improve ischemic myocardium. J. Thorac. Cardiovasc. Surg. 150, 1268–1276 (2015).

    Article  PubMed  PubMed Central  Google Scholar 

  24. Rodell, C.B. et al. Shear-thinning supramolecular hydrogels with secondary autonomous covalent crosslinking to modulate viscoelastic properties in vivo. Adv. Funct. Mater. 25, 636–644 (2015).

    Article  CAS  PubMed  Google Scholar 

  25. Rodell, C.B. et al. Injectable shear-thinning hydrogels for minimally invasive delivery to infarcted myocardium to limit left ventricular remodeling. Circ. Cardiovasc. Interv. 9, e004058 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  26. Rodell, C.B., Rai, R., Faubel, S., Burdick, J.A. & Soranno, D.E. Local immunotherapy via delivery of interleukin-10 and transforming growth factor β antagonist for treatment of chronic kidney disease. J. Control Release 206, 131–139 (2015).

    Article  CAS  PubMed  Google Scholar 

  27. Soranno, D.E. et al. Delivery of interleukin-10 via injectable hydrogels improves renal outcomes and reduces systemic inflammation following ischemic acute kidney injury in mice. Am. J. Physiol. Renal Physiol. 311, F362–F372 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  28. Highley, C.B., Rodell, C.B. & Burdick, J.A. Direct 3D printing of shear-thinning hydrogels into self-healing hydrogels. Adv. Mater. 27, 5075–5079 (2015).

    Article  CAS  PubMed  Google Scholar 

  29. Ouyang, L., Highley, C.B., Rodell, C.B., Sun, W. & Burdick, J.A. 3D printing of shear-thinning hyaluronic acid hydrogels with secondary cross-linking. ACS Biomater. Sci. Eng. 2, 1743–1751 (2016).

    Article  CAS  PubMed  Google Scholar 

  30. Lu, H.D., Soranno, D.E., Rodell, C.B., Kim, I.L. & Burdick, J.A. Secondary photocrosslinking of injectable shear-thinning dock-and-lock hydrogels. Adv. Healthc. Mater. 2, 1028–1036 (2013).

    Article  CAS  PubMed  Google Scholar 

  31. Cai, L., Dewi, R.E. & Heilshorn, S.C. Injectable hydrogels with in situ double network formation enhance retention of transplanted stem cells. Adv. Funct. Mater. 25, 1344–1351 (2015).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  32. van de Manakker, F., Kroon-Batenburg, L.M., Vermonden, T., van Nostrum, C.F. & Hennink, W.E. Supramolecular hydrogels formed by β-cyclodextrin self-association and host–guest inclusion complexes. Soft Matter 6, 187–194 (2010).

    Article  CAS  Google Scholar 

  33. Wang, L.L. et al. Injectable, guest-host assembled polyethylenimine hydrogel for siRNA delivery. Biomacromolecules 18, 77–86 (2017).

    Article  PubMed  CAS  Google Scholar 

  34. Soranno, D.E., Lu, H.D., Weber, H.M., Rai, R. & Burdick, J.A. Immunotherapy with injectable hydrogels to treat obstructive nephropathy. J. Biomed. Mater. Res. A 102, 2173–2180 (2014).

    Article  PubMed  CAS  Google Scholar 

  35. Miyajima, A. et al. Antibody to transforming growth factor-beta ameliorates tubular apoptosis in unilateral ureteral obstruction. Kidney Int. 58, 2301–2313 (2000).

    Article  CAS  PubMed  Google Scholar 

  36. Mealy, J.E., Rodell, C.B. & Burdick, J.A. Sustained small molecule delivery from injectable hyaluronic acid hydrogels through host-guest mediated retention. J. Mater. Chem. B Mater. Biol. Med. 3, 8010–8019 (2015).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  37. Roche, E.T. et al. Comparison of biomaterial delivery vehicles for improving acute retention of stem cells in the infarcted heart. Biomaterials 35, 6850–6858 (2014).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  38. Burdick, J.A., Mauck, R.L. & Gerecht, S. To serve and protect: hydrogels to improve stem cell-based therapies. Cell Stem Cell 18, 13–15 (2016).

    Article  CAS  PubMed  Google Scholar 

  39. Caliari, S.R. et al. Stiffening hydrogels for investigating the dynamics of hepatic stellate cell mechanotransduction during myofibroblast activation. Sci. Rep. 6, 21387 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  40. Rodell, C.B., Dusaj, N.N., Highley, C.B. & Burdick, J.A. Injectable and cytocompatible tough double-network hydrogels through tandem supramolecular and covalent crosslinking. Adv. Mater. 28, 8419–8424 (2016).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  41. Boekhoven, J., RubertPérez, C.M., Sur, S., Worthy, A. & Stupp, S.I. Dynamic display of bioactivity through host–guest chemistry. Angew. Chem. Int. Ed. Engl. 52, 12077–12080 (2013).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  42. Li, H., Frith, J. & Cooper-White, J.J. Modulation of stem cell adhesion and morphology via facile control over surface presentation of cell adhesion molecules. Biomacromolecules 15, 43–52 (2014).

    Article  CAS  PubMed  Google Scholar 

  43. Rodell, C.B., Wade, R.J., Purcell, B.P., Dusaj, N.N. & Burdick, J.A. Selective proteolytic degradation of guest–host assembled, injectable hyaluronic acid hydrogels. ACS Biomater. Sci. Eng. 1, 277–286 (2015).

    Article  CAS  PubMed  Google Scholar 

  44. Burdick, J.A., Chung, C., Jia, X., Randolph, M.A. & Langer, R. Controlled degradation and mechanical behavior of photopolymerized hyaluronic acid networks. Biomacromolecules 6, 386–391 (2005).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  45. Smeds, K.A. & Grinstaff, M.W. Photocrosslinkable polysaccharides for in situ hydrogel formation. J. Biomed. Mater. Res. A 54, 115–121 (2001).

    Article  CAS  Google Scholar 

  46. Sahoo, S., Chung, C., Khetan, S. & Burdick, J.A. Hydrolytically degradable hyaluronic acid hydrogels with controlled temporal structures. Biomacromolecules 9, 1088–1092 (2008).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  47. McNaughton, M., Engman, L., Birmingham, A., Powis, G. & Cotgreave, I.A. Cyclodextrin-derived diorganyl tellurides as glutathione peroxidase mimics and inhibitors of thioredoxin reductase and cancer cell growth. J. Med. Chem. 47, 233–239 (2004).

    Article  CAS  PubMed  Google Scholar 

  48. Kaya, E. & Mathias, L.J. Synthesis and characterization of physical crosslinking systems based on cyclodextrin inclusion/host-guest complexation. J. Polym. Sci. A Polym. Chem. 48, 581–592 (2010).

    Article  CAS  Google Scholar 

  49. Coin, I., Beyermann, M. & Bienert, M. Solid-phase peptide synthesis: from standard procedures to the synthesis of difficult sequences. Nat. Protoc. 2, 3247–3256 (2007).

    Article  CAS  PubMed  Google Scholar 

Download references

Acknowledgements

The authors are grateful for financial support from the National Science Foundation (DMR Award 1610525), an NIH/NIAMS training grant (T32-AR007132; M.H.C.), a postdoctoral fellowship (C.L.) from the IBSA Foundation, Switzerland, and predoctoral fellowships (C.B.R., M.H.C.) and an Established Investigator Award (J.A.B) from the American Heart Association.

Author information

Author notes

  1. Christopher B Rodell

    Present address: Present address: Center for Systems Biology, Massachusetts General Hospital, Boston, Massachusetts, USA.,

  2. Claudia Loebel and Christopher B Rodell: These authors contributed equally to this work.

Authors and Affiliations

  1. Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania, USA

    Claudia Loebel, Christopher B Rodell, Minna H Chen & Jason A Burdick

Authors
  1. Claudia Loebel
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Christopher B Rodell
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Minna H Chen
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Jason A Burdick
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

C.L., C.B.R. and M.H.C. performed the experiments and analyzed data. All authors wrote the manuscript, and J.A.B. supervised the research.

Corresponding author

Correspondence to Jason A Burdick.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Integrated supplementary information

Supplementary Figure 1 Rheological characterization of a representative CD-MeHA and Ad-MeHA hydrogel before and after covalent crosslinking (20% modified CD-MeHA mixed with 20% modified Ad-MeHA, stoichiometric ratio 1:1, 3.5% (wt/vol) polymer concentration).

(a) Frequency dependence of GH hydrogels presents an increasing storage modulus (G’) at higher frequencies. (b) Photocrosslinking in the presence of UV light and a radical photoinitiator (0.05% Irgacure 2959) induced mechanical stabilization of the material as shown by an increased G’ and reduced frequency dependence with a lack of re-arrangement (i.e. no cross-over of the G’ and G’’).

Supplementary Figure 2 Preparation of agarose well-in-well molds for culturing cellular guest-host hydrogels.

(a) Customized plastic mold made of Acrylonitrile-Butadiene-Styrene (ABS). (b) The mold is designed to fit into a 24-well plate with inserts of 8 mm length and 5 mm diameter. (c) After solidification of 2 mL agarose, molds can be used to contain injected guest-host hydrogels for culture.

Supplementary Figure 3 Reaction setup for synthesis of 6-o-monotosyl-6-deoxy-β-cyclodextrin (CD-Tos) and 6-(6-aminohexyl)amino-6-deoxy-β-cyclodextrin (CD-HDA).

Setup for (a) CD-Tos and (b) CD-HDA synthesis under anhydrous conditions.

Supplementary Figure 4 Rheological characterization of GH hydrogel replicates (20% modified CD-HA mixed with 20% modified Ad-HA, stoichiometric ratio 1:1, 7.5% (wt/vol) polymer concentration).

Frequency sweeps with G’ (filled symbols) and G’’ (open symbols) show the crossover of G’ and G’’ and the reproducibility of the measurement (n=3).

Supplementary Figure 5 Erosion and molecule release characteristics of GH hydrogels.

Examples for (a) cumulative hydrogel erosion profile and (b) FITC-BSA (0.1% (wt/vol)) release for 5% (wt/vol) GH hydrogels over 60 days (n=3, mean ± SD).

Supplementary Figure 6 In vivo fluorescence imaging of GH hydrogels pre- and post injection subcutaneously in the right flank of mice.

Representative overlay of near-infrared and black and white images taken after subcutaneous injection of 25 μl GH hydrogels (3.5% (wt/vol) and subsequently over 14 days illustrate degradation behavior in vivo (Pearl® Impulse, LI-COR, λex/λem = 785/820 nm).

Supplementary Figure 7 Confocal microscopy (calcein and ethidium staining) of encapsulated human MSCs.

Human MSCs (5x106/mL) were encapsulated in GH hydrogels (5% (wt/vol)) and high viability (95%) was observed after 24 h, scale bar 200 μm.

Supplementary Figure 8 1H NMR spectrum of methacrylated hyaluronic acid in D2O.

Methacrylate modification (26% shown) is determined by integration of the vinyl singlets (1H each, shaded green) relative to the sugar ring of hyaluronic acid (HA, 10H, shaded gray).

Supplementary Figure 9 1H NMR spectra of tetrabutyl ammonium salt of hyaluronic acid (HA-TBA) and methacrylated hyaluronic acid (MeHA-TBA) in D2O.

Modification of (a) HA with TBA salt is determined by the integration of the TBA methyl-groups (12H, shaded brown) relative to the N-acetyl group of HA (3H, shaded gray). Modification of (b) methacrylation and TBA salt is determined by the integration of the TBA methyl-groups (3H, shaded brown) and the vinyl singlets (1H each, shaded green) relative to the sugar ring of hyaluronic acid (HA, 10H, shaded gray).

Supplementary Figure 10 1H NMR spectrum of 6-o-monotosyl-6-deoxy-β-cyclodextrin (CD-Tos) in DMSO-d6.

Tosylation of CD is confirmed by integration of the methyl (3H, shaded red) and aromatic hydrogens (2H each, shaded orange), relative to the secondary hydroxyls of CD (14H, shaded gray). Anticipated minor impurities in the spectra may include trace acetone (δ = 2.10), ammonium chloride (δ = 6.98, 7.12, 2.27 (s)), ethyl ether (δ = 3.42 (q), 1.13 (t, 3H)), and water (see Supplementary Figure 11).

Supplementary Figure 11 1H NMR spectrum of 6-o-monotosyl-6-deoxy-β-cyclodextrin (CD-Tos) in DMSO-d6.

The product was not fully dried, which causes combination of the HOD peak with the hydroxyl groups of the CD ring (purple shaded), prohibiting reliable integration of the CD necessary to confirm mono-tosylation.

Supplementary Figure 12 1H NMR spectrum of 6-(6-aminohexyl)amino-6-deoxy-β-cyclodextrin (CD-HDA) in DMSO-d6.

Modification of CD with HDA is determined by integration of the hexane linker (12H, shaded red) relative to the secondary hydroxyls of CD (14H, shaded gray). Anticipated minor impurities in the spectra may include trace dimethlyformamide (δ = 7.98, 2.92, 2.08), acetone (δ = 2.10), and ethyl ether (δ = 3.42 (q), 1.13 (t, 3H)).

Supplementary Figure 13 1H NMR spectra of β-cyclodextrin modification of hyaluronic acid (CD-HA) and methacrylated hyaluronic acid (MeHA-CD) in D2O.

(a) Modification of HA with pendant CD (30.2%) is determined by integration of the hexane linkers (12H, shaded red) relative to the N-acetyl singlet of HA (3H, shaded gray). (b) CD functionalization of MeHA shows an overlap of the spectra of the modifications with the sugar ring and the N-acetyl group of HA. Therefore, to determine the modification of MeHA with CD (30.3%), the hexane linker (12H, shaded red) is integrated relative to the methacrylate modification, which is assumed to be conserved throughout the reaction (25%, 1H each, shaded green).

Supplementary Figure 14 1H NMR spectra of adamantane functionalization of hyaluronic acid (Ad-HA) and methacrylated adamantane hyaluronic acid (Ad-MeHA) in D2O.

(a) Modification of HA with pendant Ad (32.5%) is determined by integration of the ethyl multiplet (12H, shaded blue) relative to the sugar ring of HA (10H, shaded gray). (b) Modification of MeHA with pendant Ad (32.8%) is determined by integration of the ethyl multiplet (12H, shaded blue) relative to the sugar ring of HA (10H, shaded gray). Integration of the vinyl singlets (1H each, shaded green) relative to the sugar ring of hyaluronic acid (HA, 10H, shaded gray) confirms the conservation of the methacrylate modification.

Supplementary Figure 15 Confocal microscopy (calcein and ethidium staining) of rat endothelial progenitor cells (EPCs) encapsulated in GH hydrogels (5% (wt/vol)).

EPCs were not homogenously mixed with the GH hydrogel, which caused poor cell viability (45.5%) after injection through a 25G ¼ needle, scale bar 200 μm.

Supplementary information

Supplementary Text and Figures

Supplementary Figures 1–15. (PDF 1700 kb)

Supplementary Data (zip file).

Stereolithography file for plastic mold. (ZIP 118 kb)

Supplementary Video 1.

Mixing of CD-HA and Ad-HA in a tube. (MP4 2536 kb)

Supplementary Video 2.

Loading of a syringe with preformed GH hydrogels and subsequent injection. (MP4 3289 kb)

Supplementary Video 3.

Injection of GH hydrogels into customized acrylamide molds. (MP4 2381 kb)

Supplementary Video 4.

Mixing of CD-HA and Ad-HA in the back of a syringe. (MP4 2002 kb)

Rights and permissions

Reprints and Permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Loebel, C., Rodell, C., Chen, M. et al. Shear-thinning and self-healing hydrogels as injectable therapeutics and for 3D-printing. Nat Protoc 12, 1521–1541 (2017). https://doi.org/10.1038/nprot.2017.053

Download citation

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nprot.2017.053

This article is cited by

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Advanced search

Quick links

Nature Briefing: Translational Research

Sign up for the Nature Briefing: Translational Research newsletter — top stories in biotechnology, drug discovery and pharma.

Get what matters in translational research, free to your inbox weekly. Sign up for Nature Briefing: Translational Research