A kit for preparing lipid nanoparticles comprising a transfection reagent composition comprising: (a) 1,17-bis(2-octylcyclopropyl)heptadecan-9-yl-4-(dimethylamino)butanoate or pharmaceutically acceptable salts thereof; (b) 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC); (c) cholesterol; and (d) one or more surfactants selected from polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, or polyoxyethylene stearate; and a device for making lipid particles, wherein the device comprises: (i) a first well for receiving a first solution comprising a first solvent; (ii) a first channel in fluid communication with the first well; (iii) a second well for receiving a second solution comprising a second solvent; (iv) a second channel in fluid communication with the second well; (v) a third channel for receiving first and second streams flowed from the first and second wells through the first and second channels, respectively, wherein the third channel has a first region adapted for flowing the first and second streams introduced into the channel and a second region adapted for mixing the contents of the first and second streams to provide a third stream comprising particles; and (vi) a third well for receiving the third stream comprising particles. (a) 1,17-bis(2-octylcyclopropyl)heptadecan-9-yl-4-(dimethylamino)butanoate or pharmaceutically acceptable salts thereof; (b) 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC); (c) cholesterol; and (d) one or more surfactants selected from polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, or polyoxyethylene stearate; and a device for making lipid particles, wherein the device comprises: (i) a first well for receiving a first solution comprising a first solvent; (ii) a first channel in fluid communication with the first well; (iii) a second well for receiving a second solution comprising a second solvent; (iv) a second channel in fluid communication with the second well; (v) a third channel for receiving first and second streams flowed from the first and second wells through the first and second channels, respectively, wherein the third channel has a first region adapted for flowing the first and second streams introduced into the channel and a second region adapted for mixing the contents of the first and second streams to provide a third stream comprising particles; and (vi) a third well for receiving the third stream comprising particles. (i) a first well for receiving a first solution comprising a first solvent; (ii) a first channel in fluid communication with the first well; (iii) a second well for receiving a second solution comprising a second solvent; (iv) a second channel in fluid communication with the second well; (v) a third channel for receiving first and second streams flowed from the first and second wells through the first and second channels, respectively, wherein the third channel has a first region adapted for flowing the first and second streams introduced into the channel and a second region adapted for mixing the contents of the first and second streams to provide a third stream comprising particles; and (vi) a third well for receiving the third stream comprising particles.