The present disclosure is directed to polymer and polymer conjugate-based nanoparticle delivery systems for delivering biological agents, and methods of making and using these compositions. Certain embodiments of the present disclosure provide polymers comprising alternating charged and uncharged segments comprising one or more of the following structural units of Formula (I) or Formula (II) or Formula (III): wherein is an uncharged segment comprising polyalkylene glycol; and B is a cationically charged segment comprising at least one polyhydroxy linkage.