Research ArticleBIOMATERIALS

A reversible thermoresponsive sealant for temporary closure of ocular trauma

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Science Translational Medicine  06 Dec 2017:
Vol. 9, Issue 419, eaan3879
DOI: 10.1126/scitranslmed.aan3879
  • Fig. 1. Design of a thermoresponsive hydrogel to seal scleral perforation.

    (A) Schematic depicting implementation of a temperature-mediated adhesive hydrogel that adapts to wound shape and a tool for its deployment at a perforation site in the sclera. (B) Images of the changes in physical properties as the sealing hydrogel transitions from hydrophilic coils to hydrophobic globules at its lower critical solution temperature (LCST). (C) Molecular structures of formulations of poly(N-isopropylacrylamide) (PNIPAM) with butylacrylate (BA) or N-tert-butylacrylamide (NT) and a table of resulting alterations of molecular properties and LCST values. (D) Normalized scattering intensity as a function of temperature for PNIPAM, poly(NIPAM-co-NT) (N85NT15), and poly(NIPAM-co-BA) (N95BA5). A.U., arbitrary units.

  • Fig. 2. Rheological characterization and hydrogel differentiation.

    (A) Storage and loss moduli (G′ and G″, respectively) over strain for N95BA5. (B and C) G″ (B) and G′ (C) modulus representations of viscoelastic behavior for co-BA and co-NT as a function of angular frequency at fixed strain. (D) Table of storage moduli for co-NT and co-BA compositions at different angular frequencies. (E) Storage and loss moduli (G′ and G″, respectively) over frequency for co-NT and co-BA compositions. (F) Measurement of complex viscosity for N95BA5 according to temperature. (G to I) Images of square and round gel molds formed by heating the hydrogel solutions to 32°C. Scale bars, 1 cm. (J to L) Images of solid N95BA5 hydrogel demonstrating horizontal resilience (J), vertical resilience (K), and strength of form on contact (L). Scale bars, 1 cm.

  • Fig. 3. Preliminary ex vivo and in vitro hydrogel evaluation.

    (A) Schematic (top) and image (bottom) depicting ex vivo procedures carried out in a pressure-controlled explanted cadaveric pig eye. (B and C) Images (B) and schematic depiction (C) of hydrogel injection through scleral perforation by deployment of a sealant trail through the wound, leaving rivet-like caps subsequently removed to leave the occlusion flush with the scleral surface. (D) Comparison of maintained intraocular pressures across a concentration spectrum for N95BA5 and N85NT15 hydrogels (n = 3 per group). (E) Image of a solid plug removed from a test eye. (F) Schematic depicting tissue adhesion tests comparing PNIPAM, N95BA5, and cyanoacrylate adhesion strength to scleral tissue ex vivo. (G) Adhesion force of different concentrations of N95BA5, PNIPAM, and cyanoacrylate to scleral tissue; columns show 478 ± 71 and 639 ± 110 for N95BA5 and cyanoacrylate, respectively (n = 3 per group).

  • Fig. 4. Hydrogel particle size and gelation mechanism.

    (A) N95BA5 particle size as assessed using dynamic light scattering in solution below LCST (2°C), showing a 96% scattering intensity for small-radius particles. (B) Particle size in the phase transition region (12°C). A split was observed between particles with hydrodynamic radius of 4.5 and 236.2 nm. (C) Particle size toward the end of the phase transition region (18°C). Ninety-eight percent of scattering intensity was due to large-radius N95BA5 aggregates. (D to F) Hydrodynamic radius size of particles traced through the hydrogel transition to show higher aggregate populations at higher temperatures (n = 3 per temperature). (G) Gross images of molded hydrogel samples held at the expected eye temperature (32°C) for up to 30 days, showing slight volume decrease and good shape persistence and stability.

  • Fig. 5. Preliminary performance validation of the hydrogel in vivo in a rabbit model of scleral trauma.

    (A) Design diagrams (a and c) and validation (b) of a custom injection tool to effectively control hydrogel deployment and regulate its temperature. An image of the prototype injector is shown in the bottom right. (B) Two-arm study design to assess safety and efficacy of the hydrogel versus the current standard of care for posterior segment open globe injuries. (C) Images of the surgical procedure in rabbits. A 3-mm, full-thickness linear incision was created in the sclera about 3 mm radial from the limbus, followed by preparation and deployment of the hydrogel through the incision. (D) Representative baseline intraocular pressure (IOP) values showing no statistical difference between eyes of the same animal or any circadian-induced variations; columns show 6.5 ± 0.2, 6.5 ± 0.2, 5.8 ± 0.2, 6.4 ± 0.3, 8.1 ± 0.4, 8.0 ± 0.4, 7.4 ± 0.5, and 8.6 ± 0.4 mmHg (n = 28 per group). (E) Wald test comparison of mean IOP values of the treatment group versus no intervention, after procedure, showed a statistically significant improvement in mean IOP with sealant placed (*P < 0.05 and **P < 0.001).

  • Fig. 6. N95BA5 biocompatibility beyond intended use frame.

    (A) Series of histological cross sections prepared for control (left pairs) and treatment (right pairs) in hematoxylin and eosin (H&E) and Masson’s trichrome stain for each of the study endpoints (t = 48 hours, 1 week, and 4 week). Scale bars, 800 μm. (B) Increased magnification of one of the laceration margins for the treatment group showing evolution of the tissue-hydrogel interface from acute inflammatory infiltrate to a mature, compact fibrotic encapsulation layer at 4 weeks. Scale bars, 50 μm. (C) Gross visualization (top row) and high-magnification (bottom row) evaluation of treatment group retinas showing no evidence of trauma-induced retinal detachment or hydrogel-induced retinal neurotoxicity. Scale bars, 5 mm (top row) and 100 μm (bottom row).

Supplementary Materials

  • www.sciencetranslationalmedicine.org/cgi/content/full/9/419/eaan3879/DC1

    Materials and Methods

    Fig. S1. Schematic synthesis routes of the N85NT15 and N95BA5 copolymers.

    Fig. S2. 1H NMR spectrum for N85NT15 and N95BA5 copolymers in CDCl3.

    Fig. S3. Scattering intensity spectra of N95BA5 as a function of temperature.

    Fig. S4. Strain amplitude for N95BA5 and N85NT15 at T = 6°C.

    Fig. S5. Strain amplitude of N85NT15 at its LCST.

    Fig. S6. Complex viscosity of N95BA5 as a function of temperature and concentration.

    Fig. S7. Compressive stress-strain characterization and compressive modulus of the N95BA5 hydrogel.

    Fig. S8. Tensile stress-strain characterization and tensile modulus of the N95BA5 hydrogel.

    Fig. S9. Intensity distribution graph of DLS spectra for N95BA5 recorded at different temperatures.

    Fig. S10. Hydrophobic/hydrophilic nature of the N95BA5 hydrogel above and below the LCST.

    Fig. S11. Injector tool cooling reaction calibration curves for 2.5 and 12.5 g of ammonium nitrate to various volumes of added water.

    Fig. S12. Visual evaluation of eye responses to surgical procedure and sealant placement.

    Fig. S13. TRS in the hands of professionals: In vitro application at Walter Reed Medical Center.

    Table S1. Injector tool design requirements.

    Table S2. In vivo study tabulated trajectory.

    Table S3. In vivo statistical analysis of average OD/OS for groups over time.

    Table S4. Scleral tissue response at the hydrogel-sclera interface.

    Table S5. Responses from freehand write-in section of user survey administered during clinical user workshop.

    Table S6. Responses from multiple choice section of user survey administered during clinical user workshop.

    Movie S1. In vivo trauma simulation and hydrogel application procedure.

  • Supplementary Material for:

    A reversible thermoresponsive sealant for temporary closure of ocular trauma

    Niki Bayat, Yi Zhang, Paulo Falabella, Roby Menefee, John J. Whalen III,* Mark S. Humayun, Mark E. Thompson

    *Corresponding author. Email: jjwhalen{at}med.usc.edu

    Published 6 December 2017, Sci. Transl. Med. 9, eaan3879 (2017)
    DOI: 10.1126/scitranslmed.aan3879

    This PDF file includes:

    • Materials and Methods
    • Fig. S1. Schematic synthesis routes of the N85NT15 and N95BA5 copolymers.
    • Fig. S2. 1H NMR spectrum for N85NT15 and N95BA5 copolymers in CDCl3.
    • Fig. S3. Scattering intensity spectra of N95BA5 as a function of temperature.
    • Fig. S4. Strain amplitude for N95BA5 and N85NT15 at T = 6°C.
    • Fig. S5. Strain amplitude of N85NT15 at its LCST.
    • Fig. S6. Complex viscosity of N95BA5 as a function of temperature and concentration.
    • Fig. S7. Compressive stress-strain characterization and compressive modulus of the N95BA5 hydrogel.
    • Fig. S8. Tensile stress-strain characterization and tensile modulus of the N95BA5 hydrogel.
    • Fig. S9. Intensity distribution graph of DLS spectra for N95BA5 recorded at different temperatures.
    • Fig. S10. Hydrophobic/hydrophilic nature of the N95BA5 hydrogel above and below the LCST.
    • Fig. S11. Injector tool cooling reaction calibration curves for 2.5 and 12.5 g of ammonium nitrate to various volumes of added water.
    • Fig. S12. Visual evaluation of eye responses to surgical procedure and sealant placement.
    • Fig. S13. TRS in the hands of professionals: In vitro application at Walter Reed Medical Center.
    • Table S1. Injector tool design requirements.
    • Table S2. In vivo study tabulated trajectory.
    • Table S3. In vivo statistical analysis of average OD/OS for groups over time.
    • Table S4. Scleral tissue response at the hydrogel-sclera interface.
    • Table S5. Responses from freehand write-in section of user survey administered during clinical user workshop.
    • Table S6. Responses from multiple choice section of user survey administered during clinical user workshop.
    • Legend for movie S1

    [Download PDF]

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). In vivo trauma simulation and hydrogel application procedure.

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