A scaffold-free microtissue is disclosed that includes one or more gold nanostructures linked to a functional moiety, wherein the functional moiety is one or more vasculogenic peptides, one or more anti-inflammatory peptides, one or more antiapoptotic peptides, one or more antinecrotic peptides, one or more antioxidant peptides, one or more oligonucleotides, one or more lipid particles, one or more phospholipid particles, one or more liposomes, one or more nanoliposomes, one or more microRNAs, or one or more siRNAs. The scaffold-free microtissue further includes a plurality of cardiac myocytes or cardiac myoblasts, which are conjugated to the one or more gold nanostructures, wherein the plurality of cardiac myocytes or cardiac myoblasts are arranged in a cluster. The scaffold-free microtissue further includes a plurality of fibroblasts, wherein the fibroblasts are arranged in at least one layer of fibroblasts that substantially surrounds the cluster of gold-nanostructure-conjugated cardiac myocytes or gold-nanostructure-conjugated cardiac myoblasts.