. 2021 Dec 6;7(5):372–388. doi: 10.1038/s41578-021-00399-5

Table 3.

Biocompatible polymers for vaccine delivery

Polymer	Biodegradation	Properties	Vaccine delivery method	Ref.
*Polyesters*
Poly(ε-caprolactone) (PCL)	2–4 years	Does not generate acidic environment upon degradation Adjuvant properties Slow degradation only suitable for long-term delivery applications	NP, MP	¹⁸⁹
Poly(lactic acid) (PLA)	3–8 months	Tunable degradation depending on chirality of monomers Adjuvant properties	NP, MP	¹⁹⁰
Poly(lactic-co-glycolic acid) (PLGA)	1–6 months	Tunable degradation depending on monomer ratios in copolymer Degradation produces acidic environment Protein encapsulation can cause denaturation	NP, MP, MN	¹¹⁸
*Polyanhydrides*
Poly[1,6-bis(p-carboxyphenoxy)hexane-co-sebacic acid] (PCPH-SA)	2–10 weeks	Tunable degradation and material properties owing to synthetic flexibility Adjuvant properties Freezing and anhydrous conditions required for storage	NP, MP	¹²⁷
*Polyphosphazene*
Poly[di(carboxylatophenoxy)phosphazene] (PCPP)	1–24 months	Tunable degradation and material properties owing to synthetic flexibility Buffering capacity of degradation products Adjuvant properties	NP, MP, coated MN	¹⁹¹
*Polysaccharides*
Chitosan	14–60 days	Encapsulation of antigens in aqueous media Mucoadhesive properties Adjuvant properties High variability in quality from commercial sources can affect degradation and immunogenicity	NP, MP, MN, coated MN	¹⁴⁴
Hyaluronic acid (HA)	<24 hours	Rapid dissolution in the skin Adjuvant properties Not suitable for long-term delivery applications	MN	¹⁹²
Dextran	1–42 hours	Rapid dissolution in the skin Microparticle formulations require chemical modification of dextran	MP, MN	¹⁹³
Alginate	NA	Encapsulation of antigens in aqueous media Mucoadhesive properties Adjuvant properties Stable at low pH, facilitating oral immunization High variability in quality from commercial sources can affect degradation and immunogenicity Limited in vivo degradation unless chemically modified	MP, MN	¹⁹⁴
*Non-biodegradable polymers*
Polyvinylalcohol (PVA) or polyvinylpyrrolidone (PVP)	NA	Rapid dissolution in the skin Non-biodegradable	MN	¹⁹⁵

MN, microneedle; MP, microparticle; NA, not applicable; NP, nanoparticle.