**Biocompatibility Investigation of Hybrid Organometallic Polymers for Sub-Micron 3D Printing via Laser Two-Photon Polymerisation**

**Evaldas Balˇciunas ¯ 1, Nadežda Dreiže˙ 1, Monika Grubliauskaite˙ 1, Silvija Urnikyte˙ 1, Egidijus Šimoliunas ¯ 1, Virginija Bukelskiene˙ 1, Mindaugas Valius 1, Sara J. Baldock 2,3, John G. Hardy 2,3,\* and Daiva Baltriukiene˙ 1,\***


Received: 29 October 2019; Accepted: 24 November 2019; Published: 27 November 2019

**Abstract:** Hybrid organometallic polymers are a class of functional materials which can be used to produce structures with sub-micron features via laser two-photon polymerisation. Previous studies demonstrated the relative biocompatibility of Al and Zr containing hybrid organometallic polymers in vitro. However, a deeper understanding of their e ffects on intracellular processes is needed if a tissue engineering strategy based on these materials is to be envisioned. Herein, primary rat myogenic cells were cultured on spin-coated Al and Zr containing polymer surfaces to investigate how each material a ffects the viability, adhesion strength, adhesion-associated protein expression, rate of cellular metabolism and collagen secretion. We found that the investigated surfaces supported cellular growth to full confluency. A subsequent MTT assay showed that glass and Zr surfaces led to higher rates of metabolism than did the Al surfaces. A viability assay revealed that all surfaces supported comparable levels of cell viability. Cellular adhesion strength assessment showed an insignificantly stronger relative adhesion after 4 h of culture than after 24 h. The largest amount of collagen was secreted by cells grown on the Al-containing surface. In conclusion, the materials were found to be biocompatible in vitro and have potential for bioengineering applications.

**Keywords:** bioactive surfaces; biomaterials; hybrid organometallic polymers; laser two-photon polymerisation; tissue engineering
