Goats from the Zagros Mountains may represent the earliest examples of goat herding.
Image credit: The Central Zagros Project.
Edited by David A. Weitz, Harvard University, Cambridge, MA, and approved August 14, 2015 (received for review May 13, 2015)
Significance
In this paper we present results on 3D, multiscale laser machining of soft, transparent biomaterials suited for cellular growth and/or implantation. We use an ultrafast laser to generate high-resolution, 3D structures within the bulk of a transparent soft-biomaterial formulation that can support cell growth and allow cells to penetrate deep within the material. The structure is created by multiphoton absorption which, thanks to the clarity of the silk gels, is possible nearly 1 cm below the surface of the material. This depth represents an ∼10× improvement over other materials. The ability to create micrometer-scale voids over such a large volume has promising applications in the biomedical field and its efficacy was demonstrated both in vitro and in vivo.
Abstract
Light-induced material phase transitions enable the formation of shapes and patterns from the nano- to the macroscale. From lithographic techniques that enable high-density silicon circuit integration, to laser cutting and welding, light–matter interactions are pervasive in everyday materials fabrication and transformation. These noncontact patterning techniques are ideally suited to reshape soft materials of biological relevance. We present here the use of relatively low-energy (< 2 nJ) ultrafast laser pulses to generate 2D and 3D multiscale patterns in soft silk protein hydrogels without exogenous or chemical cross-linkers. We find that high-resolution features can be generated within bulk hydrogels through nearly 1 cm of material, which is 1.5 orders of magnitude deeper than other biocompatible materials. Examples illustrating the materials, results, and the performance of the machined geometries in vitro and in vivo are presented to demonstrate the versatility of the approach.
Footnotes
- ↵1To whom correspondence should be addressed. Email: fiorenzo.omenetto{at}tufts.edu.
Author contributions: M.B.A., B.M., D.L.K., and F.G.O. designed research; M.B.A. and J.E.M. performed research; J.C., B.P.P., J.E.M., and J.P.M. contributed new reagents/analytic tools; M.B.A., J.E.M., B.M., and F.G.O. analyzed data; D.L.K. and F.G.O. supervised the project; and M.B.A. and F.G.O. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1509405112/-/DCSupplemental.
3D laser machining of biocompatible hydrogels
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