Zwitterionic hydrogel coating for medical devices

The surface the body ignores.

ZwiGuard is a zwitterionic hydrogel coating, covalently bonded to the device, that keeps protein, cells and bacteria off. Less scar, lower impedance, easier insertion, fewer bacteria. One coating step. Ten years of evidence.

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Horizontal bar chart of 10 measurements of scar capsule or fibrosis around coated surfaces compared with uncoated, in mice, rats and sheep, four weeks to one year, from four papers (Horne 2023, Peel 2024, Barrera 2026, Ben-Shlomo 2026). Reductions run from about 45 to about 85 percent. The sheep basal-turn bar, about 78 percent, is drawn hollow because it is not significant.

Less scar tissue around coated surfaces in mice, rats and sheep: percent reduction in fibrotic capsule or fibrosis, measurement by measurement. The hollow bar is not statistically significant.

Source: 10 measurements in mice, rats and sheep. Horne 2023, Acta Biomaterialia; Peel 2024, ACS Applied Bio Materials; Barrera 2026, ACS Applied Polymer Materials; Ben-Shlomo 2026, Hearing Research. Values read from the published figures; the basal-turn bar is not significant.

  • 01 Thicknessa few micrometres to 100 or more, tunable
  • 02 Bondgel tears before the interface lets go (Leigh 2019)
  • 03 Impedanceabout half, four weeks in sheep (Ben-Shlomo 2026)

Every number on this site comes from a published paper, dissertation or issued patent.

And behind the papers: 182 archived experiments, 1,056 adhesion tests, 136 animals.

Sources: the ten journal papers and the dissertations listed on the Publications page, USPTO records, ZCMI patent schedule, 2025.

Less scar

Scar tissue was about 45 to 85 percent lower around coated surfaces.

Ten measurements from four papers, in mice, rats and sheep, from four weeks to one year, on silicone and on real implant arrays. The sheep basal-turn measurement was not statistically significant.

In mice, the capsule was 67 percent thinner at six weeks on flat silicone and 62 percent thinner at one year on coated cochlear implant arrays (Horne 2023, Acta Biomaterialia).

Capsule thickness in mice. At six weeks on flat silicone the zwitterionic coating gave a capsule 67 percent thinner than uncoated, while a non-zwitterionic hydrogel control did not differ significantly. At one year on human cochlear implant arrays the coated capsule was 62 percent thinner.

In mice, scar capsules were 67 percent thinner around zwitterionic-coated silicone at six weeks and 62 percent thinner around coated human cochlear implant arrays at one year. A non-zwitterionic hydrogel control did not differ significantly from uncoated.

Source: Horne R, Ben-Shlomo N, Jensen M, et al. Acta Biomaterialia 2023;166:212-223, Figs 5D and 7I (means and p values from the text; SEM whiskers approximate, read from the published figure). doi:10.1016/j.actbio.2023.05.011

Lower impedance

Coated implant arrays read about half the impedance of uncoated ones.

Working human cochlear implant arrays in sheep read 67 percent lower impedance at implantation and 47 percent lower four weeks later.

Three sheep, one coated and one uncoated array each (Ben-Shlomo 2026, Hearing Research). No coated device has been implanted in a person.

Bar chart of total electrode impedance in sheep. Coated ears read 67 percent lower than uncoated ears at implantation and 47 percent lower four weeks later.

Electrode impedance of coated versus uncoated cochlear implant arrays in sheep.

Source: Ben-Shlomo et al. 2026, Hearing Research 474:109606, Fig 3B (values read from the figure).

Easier insertion

Insertion force fell by about 40 percent.

Coated cochlear implant arrays needed 37.0 mN of peak force against 64.2 mN for uncoated arrays, in human cadaveric cochleae (n = 9 per group, p = 0.001).

Force variation during insertion fell from 89.9 to 52.1 mN/s (p = 0.03). Bennion 2021, Otology and Neurotology.

Two bar charts for coated and uncoated cochlear implant arrays in human cadaveric cochleae, nine per group. Peak insertion force was 64.2 millinewtons uncoated and 37.0 coated, 42 percent lower (p = 0.001). Force variation was 89.9 millinewtons per second uncoated and 52.1 coated, 42 percent lower (p = 0.03).

Coated cochlear implant arrays needed about 40 percent less peak force, and had about 42 percent less force variation, than uncoated arrays in human cadaveric cochleae.

Source: Bennion DM, Horne R, Peel A, Reineke P, Henslee A, Kaufmann C, Guymon CA, Hansen MR. Otology and Neurotology 2021;42(10):1476-1483. doi:10.1097/MAO.0000000000003288 (Fig 4A and 4B; means and SD from the text).

Fewer bacteria, less friction

Protein, cells, bacteria and friction all fall by about 90 percent.

Across 38 published comparisons of coated and uncoated surfaces, from eight papers, the median reduction was 94 percent. The range was 53 to 99 percent.

The four groups are fibrinogen adsorption, cell attachment, S. aureus and S. epidermidis adhesion, and friction. These are laboratory and explant measurements, not clinical results.

Browse and filter every comparison on the evidence page.

Horizontal bar chart of 38 comparisons of coated versus uncoated surfaces from eight papers, grouped into four bands, as percent reduction. Protein: six bars, 91 to 98 percent. Cells: 16 bars, 53 to 99 percent. Bacteria: seven bars, 84 to 97 percent. Friction: nine bars, 84 to 96 percent. The median reduction is 94 percent.

Protein, cells, bacteria and friction: every published bench comparison of coated versus uncoated surfaces (38 bars from 8 papers), as percent reduction.

Source: 38 comparisons from 8 papers, 2017 to 2026: Leigh 2017 Biomacromolecules; Leigh 2019 Langmuir; Jensen 2021 ACS Biomaterials Science and Engineering; Shen 2021 ACS Applied Bio Materials; Bennion 2021 Otology and Neurotology; Horne 2023 Acta Biomaterialia; Peel 2024 ACS Applied Bio Materials; Barrera 2026 ACS Applied Polymer Materials. Bar values approximate where marked, read from the published plots.

It stays on

The film was still intact at one year in mice.

Checkpoints run from two weeks in rats to one year in mice. Antifouling was unchanged at six months (Horne 2023, Peel 2024).

The hydrogel is covalently grafted, so it is part of the surface rather than a layer on top of it.

Full durability record

Timeline of in vivo checkpoints. At two weeks in rats the coating still repelled S. aureus. At three weeks in mice friction was unchanged. At four weeks in a sheep cochlea there was no delamination. At six months in mice antifouling was unchanged. At one year in mice the film was intact and the capsule about 60 percent thinner.

In-vivo durability checkpoints from two weeks to one year.

Source: Shen 2021; Peel 2024; Ben-Shlomo 2026; Horne 2023.

Dip coating in our lab: the device is lowered into the monomer solution, then moved under UV light to cure. Phone footage, not the automated jig.

The process

One dip, one UV step.

The part is dipped into the monomer solution, then moved under UV light. One UV step grafts the film and crosslinks it.

Applications

Nine device families, one number that matters for each.

How we work together

Three steps, and the first one is free.

  1. Feasibility, free

    You send parts. We coat them, with no cap on quantity, and return them with matched uncoated controls and our data.

  2. Joint development

    We optimize the coating on your production devices and run ISO 10993, sterilization, aging and an animal model.

  3. Manufacturing

    We coat for you. Our FDA Device Master File sits behind your submission.

Origin
University of Iowa spin-off.
Funding
NIH SBIR Phase I and Phase II.
Patents
US 11,525,069; 11,814,526; 12,116,498.
Papers
Ten peer-reviewed papers.

Bring us a device with a fouling, scar or friction problem.

We coat it free, with no cap on quantity, and return it with matched uncoated controls and data.

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