Table 2: Common Polymers for Drug Delivery Applications.

Polymers indicated by broad classifications including biologically sourced polymers (proteins and saccharides), and biosynthetic polymers. Example(s) of these polymers indicated with associated properties such as molecular weight, soluble solvent systems, degree of hydrophilicity/hydrophobicity, ionic charge, and typical degradation mechanisms. Acronyms: HFP, hexafluoropropylene; TFE, trifluoroethanol; PBS, phosphate buffer saline; EtOH, ethanol; THF, tetrahydrofuran; HFIP, hexafluoro-2-propanol; DMF, dimethylformamide. Example chemical structures taken from Bio Render (Proteins/peptides and Saccharides) and Sigma-Aldrich for the remainder.

Classification	Examples	Molecular Weight (kDa)	Compatible Solvent System(s) and Solubility	Ionic Charge	Major Degradation Mechanisms	Ref.
Readily Biodegradable Polymers
Proteins/Peptides	Collagen (I)	300	HFP, TFE, PBS/EtOH	Neutral	Enzymatic	[33, 34]
	Elastin	60–70	Water/EtOH (40% alcohol content solubility)	Anionic	Enzymatic	[35, 36]
	Resilin	28.1	Alkaline (pH 8.2) water/PBS	Neutral	Enzymatic	[37–39]
Saccharides (glucose)	Chitosan	50–2000	Insoluble in aqueous systems, increases in water with decreasing pH (< 6.5)	Cationic	Enzymatic	[33, 40, 41]
	Alginate	32–400	Water and organic solvent insoluble, Increases at lower pH	Anionic	Dissolution	[33, 42, 43]
	Cellulose	30–200	Insoluble, increases in acidic and alkaline environments	Anionic	Enzymatic, Hydrolysis	[33, 44–46]
Polyamino acids (PLL)	Poly-lysine (PLL)	70–150	Polar solvents (water, dimethyl sulfoxide, DMF)	Cationic	Enzymatic, Hydrolysis	[47]
Polyanhydrides (PSA)	Poly-sebacic anhydride (PSA)	0.1–137	Organic solvents (dichloromethane), slightly water soluble	Neutral	Surface Erosion	[48, 49]
Polyesters (PLA)	Poly-lactic acid (PLA)	128–152	Dioxane, acetonitrile, chloroform (water insoluble)	Neutral	Hydrolysis	[50, 51]
	Polycaprolactone (PCL)	14	Methylene chloride, anisole (lower MW aqueous solubility)	Neutral	Enzymatic, Hydrolysis	[52, 53]
	Poly-glycolic acid (PGA)	20–140	HFIP (low water and organic solvent solubility)	Neutral	Enzymatic, Hydrolysis	[54, 55]
	Poly-lactide-co-glycolide (PLGA)	10–100	THF, ethyl acetate, dichloromethane (poor water solubility)	Neutral	Hydrolysis	[56, 57]
Polymers with Very Limited Biodegradation
Polyethers (PEG)	Polyethylene glycol (PEG)	20	Polar solvents (water, acetone, EtOH)	Neutral	Enzymatic (oxidative)	[58]
	Polypropylene glycol (PPG)	0.5–3.5	Water, acetone, diethyl ether	Neutral	Enzymatic (oxidative)	[58]
Polymethacrylates (HEMA)	2-Hydroxyethyl Methacrylate p(HEMA)	2–50	Organic polar solvents (alcohols), relatively water soluble with increasing MW	Neutral	Dissolution	[59, 60]
Polyvinyls (PVA)	Poly-vinyl alcohol (PVA)	26.3–30	Polar solvents (water, dimethyl sulfoxide)	Neutral	Enzymatic (oxidation), Hydrolysis	[61, 62]