Growth factor delivery
Potent, unstable, and short-lived — why delivering growth factors is harder than choosing them.
Growth factors are the signalling corner of the triad, and delivering them is consistently harder than identifying them. Common factors in bone tissue engineering include VEGF, BMP-2, and deferoxamine, and the recombinant BMPs — BMP-2, -4, -6, -7, and -9 — stimulate local bone regeneration by signalling mesenchymal stem cells to differentiate into osteoblasts.
The problem is that these proteins are inherently unstable and their activity window after release is brief, while excessive expression may provoke unwanted side effects. Loading factors onto a scaffold by different delivery strategies alters their release kinetics and effective concentrations — so the carrier, not the molecule, often determines the outcome. This is the lesson of BMP-2's clinical history.
The frontier is sequence rather than dose: native repair presents factors in an order — vessels before matrix — and reproducing that choreography is the aim of Controlled release kinetics and of dual systems described in Chitosan in tissue engineering.
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