Evaluation of different biomaterials is being performed with various methods trying to simulate the closest hostile-like in vitro environments. However the complexity of the conditions usually limits practically feasible combination of most relevant chemical, biological, biomechanical parameters in one single test. Many biomaterials and tissue engineering developments rely on high-throughput screening to multiply number of specimens and thus to gather sufficient data. The price to be paid for these methods is limited number of physical readouts, increased inter-specimens scatter, and unavoidable spatial constrains driving the conditions away of the clinical scenarios. For orthopaedic biomaterials this is of a particular concern, as implantation site conditions cannot be squeezed too much without lost of natural-mimicking stimuli.

Here we are presenting another approach based on high-output screening of biomaterials, which is based on the strategy of raising the number of readouts obtainable from every specimen at more clinically-relevant conditions. On the contrary to common methods like ISO 10993 or simplified biomechanical tests, the biomaterials enhanced simulation testing (BEST) evaluates specimens without pre-selected biomaterial model, assessing the whole specimen as would happen in the implantation site. Besides reducing the risk of improper conclusions caused by wrong material model choice, the data processing with non-local method intrinsically includes the test history bypassing common challenges usually seen with hereditary integration. For properly designed experiment, readouts might include invariant moduli, viscous stiffness, fluidity, fluid permittivity and diffusivity (without need for pressure-driven separate tests), fluid source, effective channel size, and swelling pressure (if swelling is present) in addition to conventional biomechanical parameters.

New solutions in advanced and consistent evaluations for biomaterials allow better risks control, shorten lead development time and costs, and compliant with 3R-strategy (2010/63/EC) and new regulatory requirements (2012/0266/COD in EU and FY2017 regulatory priorities by FDA). The approach shown is able to combine scientifically based tests with multi-purpose protocols to secure patient safety by screening of biomaterials under proper conditions.

The authors thank Finnish Agency for Innovations (Tekes) for providing partial financial support.

Use of scaffolds for articular cartilage repair (ACR) has increased over the last years with many biomaterials options suggested for this purpose. It is known that scaffolds for ACR have to be optimally biodegradable with simultaneous promotion of chondrogenesis, favouring hyaline cartilage formation under rather complex biomechanical and physiological conditions. Whereas improvement of the scaffolds by their conditioning with stem cells or adult chondrocytes can be employed in bioreactors, “ideal” scaffolds should be capable of performing such functions directly after implantation. It was previously considered that scaffold structure and composition would be the best if it mimics the structure of native cartilage. However, in this case no clear reparative stimuli are being imposed on the scaffold area, which would drive chondrocytes activity in a desired way.

In this work, we studied new xeno-free, recombinant human type III collagen-laden polylactide (PLA) mesh scaffolds, which have been designed, produced, and biomechanically optimized in vitro and in vivo validated in a porcine and equine model. The scaffolds were additionally assessed for relative performance simulated synovial fluids for both human conditions and veterinary cases.

It was experimentally shown that success of the scaffolds in ACR eventually require lower stiffness than surrounding cartilage yet matching the strain compliance, different in static and dynamic conditions. This ensures an optimal combination of load transfer and oscillatory nutrients supply to the cells, which otherwise is difficult to rely on just with a passive diffusion in avascular cartilage conditions. The results encourage further development of such scaffold structures targeted on their best clinical performance rather than trying to imitate the respective original tissue.

The authors would like to thank Finnish Agency for Innovation (Tekes) for providing financial support to this project. A.Z. also acknowledges Teknos Foundation (Finland) for the scholarship.