Bone graft carrier

A carrier is everything in a bone graft putty or paste that is not the graft itself. Its job is mechanical and temporary: to hold the particles together as one mass while they are shaped and placed, and — depending on the design — to keep holding them for some period after closure. The literature also calls it a binder, an excipient or a vehicle.

The materials in use are collagen (of bovine or porcine origin), gelatin, carboxymethylcellulose, glycerol, poloxamer 407, hyaluronic acid, calcium sulfate, and hydrogels of various polymers. The 2013 review in Acta Biomaterialia framed the design question in its title: are hydrogels in mouldable bone substitutes “sticky excipients or advanced 3-D carriers?” — a binder that disappears at once, or a matrix that participates in healing.

Calder and colleagues (2025) reviewed the carriers in commercial putties and reported that most resorb within days, after which the particle scaffold collapses; carboxymethylcellulose is more stable but does not form a three-dimensional scaffold. The choice of carrier also determines the origin of the product: collagen and gelatin carriers are of animal origin, cellulose and poloxamer are not.

On this site

The carrier in the composition under development is an alginate hydrogel of seaweed origin, chosen so that the finished composition contains no animal- or human-derived carrier. Whether it behaves as a matrix rather than an excipient is a development objective; see how the composition is designed and the state of evidence.