A vascular closure device includes both a mechanical component and a biological component for sealing an arteriotomy. The mechanical component reduces the size or closes the arteriotomy. The biological component covers and fills any spaces or cracks present after the arteriotomy has been mechanically reduced in size. An exemplary embodiment includes a suture or clip to approximate the edges of the arteriotomy, and a smooth rounded plug is advanced along the suture towards the closed arteriotomy. In situ, the plug transforms to a flowable or gel state and fills and covers any cracks and spaces along the closed arteriotomy.