French scientists have developed a photochemical method for patterning biomolecules inside glass capillary tubes. The technique could lead to lab-on-capillary devices as cheaper alternatives to lab-on-a-chip medical diagnostics, they claim.

Eric Defrancq, at Joseph Fourier University, Grenoble, and colleagues say their lab-on-capillary vision poses considerable challenges. 'Retaining the functionality and patterning of biomolecules in the closed environment of a capillary tube is difficult because there is no easy access to the inside surface,' explains Defrancq. 

Defrancq overcame these challenges by grafting patterns of aminooxy groups masked with photo-cleavable protecting groups to the inside surface of the capillaries. By shining light on the tubes, he cleaved the protecting groups. The exposed aminooxy groups then reacted with aldehyde groups in the peptide and carbohydrate biomolecules, fixing them to the side of the tubes. 'This method of attaching molecules in patterns allows us to position not just one biomolecule but many,' explains Defrancq.

Once in place, the biomolecules can bind cell proteins or antibodies present in biological fluids that are flushed through the tube. These protein and antibody biomarkers can be used to identify disease risk or progression or measure the effect of treatments. Different biomolecules can be attached in the one tube, which permits multi-analyses to be performed in one experiment.

'The challenge now is to use these techniques to attach more complex carbohydrates and proteins without losing the recognition properties of the immobilised biomolecule for its target,' says Defrancq. 'It is only too easy to lose recognition during the immobilisation process through either the chemistry or the methods used.' 

Janet Crombie

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