Direct laser writing (DLW) is an advanced way of structuring materials with light, without the use of a mask. Instead, a tightly focused laser beam scans a photosensitive material, creating a structure directly from a computer model. In this way it is like a 3D printer – but one with unmatched spatial resolution and material choice.

Since its introduction about a decade ago, DLW has become a staple tool of many modern laboratories, crafting structures for use in micro-optics, nano-photonics, micro-fluidics, labs-on-chips and various other disciplines. In principle, it could also herald a marked improvement in tissue engineering as a highly effective way of creating a scaffold in which cells can be grown and integrated with human tissue.

Cartilage cells, or chondrocytes, for instance, have already been shown to benefit from the 3D porous environment of a scaffold, because such a scaffold resembles native cartilage. If chondrocytes could be effectively grown on a biocompatible DLW scaffold it would be good news for the many people who annually suffer osteochondral injuries – fractures of the cartilage at the ends of bones.

Despite the potential of DLW for tissue engineering, complex structures created by the technique have until now not been tested inside living organisms, according to laser physicist Mangirdas Malinauskas at Vilnius University and colleagues. "The manufacturing technique is quite sophisticated, and up to now only state-of-the-art setups worldwide can offer the required throughput in order to produce specimens for clinical experiments," says Malinauskas.

That is why Malinauskas teamed up with materials scientists, manufacturing technologists, biochemists and medics at various other Lithuanian institutions to test a scaffold made from SZ2080, a hybrid organic-inorganic photopolymer consisting of organic acrylates and inorganic silicon and zirconium. DLW structured the scaffold, which was the size of a grain of rice, with a 3D network of micro-hexagons in which chondrocytes could be grown. The scientists implanted versions of the scaffold into rabbits, and removed them after one to six months to find out how much of the desired natural-like cartilage tissue remained.

The found that the scaffolds exhibited comparable biocompatibility to commercially available collagen membranes – a result that bodes well for studies with human cells and, eventually, clinical trials. "Currently this research is being performed, [and we are] hoping to obtain positive results in the near future," says Malinauskas.

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