The present application provides a method of making a particle comprising (i) obtaining a first solution comprising a negatively charged polysaccharide; (ii) obtaining a second solution comprising a positively charged polysaccharide; and (iii) mixing the first solution and the second solution to obtain a suspension comprising the particle. The present application also provides a method of making a therapeutic particle, comprising: (i) obtaining a solution comprising a therapeutic protein; (ii) obtaining a first suspension comprising the particle comprising a negatively charged polysaccharide and a positively charged polysaccharide, and (iii) mixing the solution of the therapeutic protein and the first suspension to obtain a second suspension comprising the therapeutic particle. The present application also provides particles (e.g., therapeutic particles) prepared by any one of the disclosed methods, as well as the compositions comprising such particles, and methods of treating a disease or condition using such particles and compositions.