article posted 4 April 2016
Himanshu Jain is the T.L. Diamond Distinguished Chair in Engineering and Applied Science, and Professor of Materials Science and Engineering at Lehigh University. He is a recipient of the Otto Schott Research international prize, Zachariasen international award for outstanding contribution to glass research, Alfred University’s Scholes Lecture award, Lehigh University’s Libsch award for research and Hillman award for long-term excellence, Fulbright Fellowship for lecturing and research at Cambridge and Aberdeen universities in UK, and a Humboldt Fellowship for research in Germany. An author of over 350 research publications, editor or author of nine books, inventor of four patents, a Principal Editor of Journal of Materials Research, he is a Fellow of the American Ceramic Society. His current research interests include: functionality in glass through fundamentals; glass surfaces; corrosion of glass in relation to manufacturing; light-induced phenomena in glass; nano-macro porous glass bioactive scaffolds for bone regeneration; conductivity and dielectric properties of amorphous and crystalline ceramics; glasses for IR biosensors, photo- and nano-lithography, and photonics; active single-crystal architecture in glass; and metal–glass nano-composites.
Interactions of glass with the living world: impact of nanoheterogeneity
Roman Golovchak1,2, Tia J. Kowal3, Ukrit Thamma1, Matthias M. Falk3 & Himanshu Jain1,*
1 International Materials Institute for New Functionality in Glass, Lehigh University, Bethlehem, PA 18015, USA
2 Physics Department, Austin Peay State University, Clarksville, TN, USA
3 Department of Biological Sciences, Lehigh University, Bethlehem, PA 18015, USA
Figure 1. Nanoscale phase separation in commonly used 45S5 Bioglass can have spinodal or droplet structure, depending on processing conditions
Often glass, which is made traditionally by quenching a melt, is considered a homogeneous solid by its users. This has been true certainly in the biomedical field, where, for example, the most widely used 45S5 sodium calcium phosphosilicate glass is assumed to be a single phase bioactive material. However, now we are learning that it is not only phase separated at nanoscale (Fig. 1), but in fact living cells recognize the nanoheterogeneity and respond accordingly; their response is significantly affected by the nature of phase-separated nanostructure (Fig. 2). We have also discovered that more than ten thousand times larger cells respond differently on nano-macro porous calcium silicate bioactive scaffolds that differ only in the size of nanopores, for example, 4 nm vs. 18 nm. These observations demonstrate the importance of nanostructure for the performance of glass products in dental and bone regeneration applications. Then it becomes crucial to develop glass fabrication processes for a given chemical composition, which will yield desired nanostructure of the ultimate product. In this presentation we will review and discuss these specific processes, which are broadly based on the conventional melt-quench and sol-gel methods of glass making. We will show how the variables like melt temperature, cooling rate, sample size of the former method affect the nanostructure (for example, interconnected vs. droplet-type distribution of phases, see Fig. 1), or gelation time, type/amount of catalyst, drying conditions, sample configuration, etc. affect the nano/macro porosity that results from the latter process. Examples of the correlation between processing conditions with the nanostructure and the performance of the final product (such as attachment and proliferation of MC3T3 pre-osteoblast) will be presented.
Figure 2. Comparison of the response of bone forming cells to nanoscale phase separated 45S5 glass with spinodal and droplet structure seen in Fig. 1. Here cell nuclei appear blue, actin fibers green and focal adhesions red