The invention provides compositions of matter comprising a cowpea chlorotic mottle virus capsid protein (CCMV CP) and a ribonucleic acid, as well as methods for using such compositions. In such compositions, the cowpea chlorotic mottle virus capsid protein envelops the ribonucleic acid so as to for a capsid that can inhibit the degradation of the ribonucleic acid (e.g. by RNAses). A method of delivering a ribonucleic acid into the cytoplasm of a mammalian cell is also provided. Typically, the method comprises the steps of combining the mammalian cell with a composition of matter described herein under conditions selected to allow the cowpea chlorotic mottle virus capsid to contact the mammalian cell and deliver the ribonucleic acid into the cytoplasm of a mammalian cell.