Ricardo Donate, Mario Monzón, Zaida Ortega, Ling Wang Evaluation of different combinations of biomaterials for bone regeneration Biomaterials and Additive Manufacturing: Osteochondral Scaffold innovation applied to osteoarthritis – BAMOS (H2020-MSCA-RISE-2016-734156) Ricardo Donate, Mario Monzón, Zaida Ortega, Ling Wang

Promote international and intersectoral collaboration through research and innovation staff exchanges. Sharing knowledge and ideas from market to research. The project particularly addresses the challenges in osteoarthritis treatment by providing novel cost effective osteochondral scaffold technology for early intervention.

PhD thesis: Experimental study of different combinations of biomaterials with polylactic acid matrix in additive manufacturing with biomedical purposes. Objectives Formulating biomaterial blends able to provide improved properties in tissue engineering support structures applicable to the bone-cartilage interface. Determining the mechanical and chemical characteristics of scaffolds obtained by additive manufacturing. Cartilage part Bone part Funded under pre-doctoral scholarship of the Government of the Canary Islands (call 2017).

Blends studied (wt:wt): Biodegradable Bioresorbable Good mechanical properties Suitable for AM Acid degradation Poor osteoconductivity Poor cell attachment Matrix: PLA Additivation Buffering agent: CaCO3 Osteoconductivity and reinforcement: β-triclacium phosphate (β-TCP) Blends studied (wt:wt): PLA PLA:CaCO3 95:5 PLA:β-TCP 95:5 PLA:CaCO3:β-TCP 95:2.5:2.5 Rectangular samples were manufactured by compression moulding in a Collin P 200 P/M press with dimensions of 80x10x1 mm

Water Contact Angle measurement (WCA) The WCA was determined at room temperature. Measurement of the static contact angle of 2 µL distilled water droplets onto the surface of the samples. Reported contact angles are the average of 25 measurements per group (five measurements per sample). The test was carried out both on dry and pre-wetted samples. Optical contact angle measuring device (JC2000D2, Shanghai Zhongchen Digital Technology Apparatus Co., Ltd.) equipped with StreamPix software (XJTU facilities).

Water Contact Angle measurement (WCA) WCA in pre-wetted state (º) Materials blend WCA in pre-wetted state (º) PLA 88.85 ± 2.24 PLA:CaCO3 95:5 84.34 ± 4.17 1 PLA:β-TCP 95:5 83.56 ± 3.59 1 PLA:CaCO3:β-TCP 95:2.5:2.5 84.05 ± 3.46 1 1 *** p<0.001 compared to the group of pure PLA simples Previous hydration of the samples has an effect on their wettability, as no statically significant difference (p>0.05) of WCA was obtained in dry state. The addition of CaCO3 and β-TCP effectively reduce the WCA of the PLA matrix in pre-wetted state.

Mechanical characterization Flexural tests were performed in displacement control mode at a crosshead speed of 1 mm/min. 3 points bending test was carried out. Five replicas of samples of each combination of materials were used to obtain the flexural modulus and the maximum flexural stress. The parameters were calculated according to the procedures explained in the standard ASTM D790-15. SANS CMT4304, MTS Systems Co. Ltd. universal testing machine (XJTU facilities).

Mechanical characterization The value of the flexural modulus and the maximum flexural stress remains unchanged between the groups (p>0.05), with the first property ranging from 3.1 to 3.3 GPa and being the second one between 19-23 MPa for the four groups of samples evaluated. 3-points bending test

Conclusions In contrast to the dry test, in the pre-wetted state of the samples the use of the additives led to a significant reduction of the WCA, i.e., greater surface wettability. In the present study, a very high statistically significant difference (p<0.001) was obtained when comparing the pure PLA scaffolds group with the composite groups of samples, with mean reduction of a 5.5% in WCA. The decrease of the hydrophobicity of surface could lead to enhanced cell attachment in the case of the composite scaffolds. In terms of mechanical properties, no significant differences were observed between the values of the samples. In this way, it would be possible to adjust the characteristics of the scaffold for bone regeneration to achieve greater cell adhesion ability while maintaining the mechanical properties of the base material.

Further information http://risebamos.eu/ http://cfi.ulpgc.es/ http://risebamos.eu/ http://cfi.ulpgc.es/ mario.monzon@ulpgc.es ricardo.donate@ulpgc.es Further information The authors would like to thank H2020-MSCA-RISE program, as this work is part of developments carried out in BAMOS project, funded from the European Union's Horizon 2020 research and innovation programme under grant agreement Nº 734156.

Ricardo Donate, Mario Monzón, Zaida Ortega, Ling Wang Evaluation of different combinations of biomaterials for bone regeneration Biomaterials and Additive Manufacturing: Osteochondral Scaffold innovation applied to osteoarthritis – BAMOS (H2020-MSCA-RISE-2016-734156) Ricardo Donate, Mario Monzón, Zaida Ortega, Ling Wang