Can you use artificial substances to repair a pcl?

Not likely. Graft tissue usually is obtained from the patient or from a cadaver. Synthetic tissues (goretex) have proven unreliable for ligament reconstruction.
No. There have been attempts to use synthetic grafts or scaffolds to reconstruct torn ligamants, but these have been unsuccessful because over time all non-biologic products will eventually fatique and break. In the future, it is possible that there will be biologic products that are produced "in vitro" (artificially) as opposed to obtained "in vivo" (from a live organism), but these do not exist now.