Table 2.

Chemical surface modification or physical modification of PEEK.

Substances involved in modification	Modification strategy	Experimental category	Evidence of improved anti-inflammatory effects	Reference
Ca2+	Poly(norepinephrine) wrapping and Ca(OH)2 solution immersion	in vitro	Decreased TNF-α and IL-1α levels and increased IL-10 levels	[76]
	IL-4 and Ca2+ grafted onto a hybrid coating consisting of polylactic acid, ALN and nano-HA	in vitro	Promoted M2 polarization of macrophages, decreased the level of TNF-α, and increased the level of IL-10	[77]
		in vivo	Promoted M2 polarization of macrophages	[77]
Phosphate group	Plasma treatment and subsequent phosphorylation reaction	in vitro	Decreased TNF-α and increased IL-10 production by macrophages	[78]
Phosphonate group	Diazonium chemistry grafting	in vivo	Decreased fibrous capsule production	[79]
Sulfonate	One-step ultraviolet-initiated graft polymerization	in vitro	Reduced secretion and gene expression levels of the proinflammatory cytokine TNF-α	[80]
β-TCP	Construction of β-TCP coating	in vitro	Promoted M2 polarization of macrophages	[81]
Zn2+	Customized magnetron sputtering technique	in vitro	Decreased expression levels of the inflammatory factors TNF-α and IL-6 and increased expression levels of the anti-inflammatory cytokines IL-4 and IL-10	[82]
Mg2+	Complex PA/Mg ion coating	in vivo	Promoted M2 polarization of macrophages and inhibited fibrous tissue formation	[83]
Sr2+	Formation of 3D porous nanomesh structures by concentrated sulfuric acid and plasma treatment	in vitro	Down-regulated the expression of proinflammatory genes, such as COX-2 and TNFα, up-regulated the expression of the anti-inflammatory gene IL-10, and promoted M2 polarization of macrophages	[84]
CS-Sr	Integration into PEEK surfaces via PDA	in vitro	Promoted cell adhesion and diffusion, improved angiogenic activity, reduced the mRNA expression of proinflammatory factors TNF-α and IL-1β	[85]
		in vivo	Reduced the inflammatory response	[85]
Cu2+	Deposited on a sulfonated PEEK surface by magnetron sputtering technique	in vitro	Promoted M2 polarization of macrophages	[86]
Ag+	Integration into PEEK surfaces via PDA	in vitro	Down-regulated the mRNA expression of proinflammatory cytokines IL-1β, IL-6, iNOS, and TNF-α and promoted M2 polarization of macrophages	[87]
SB	Sulfonated PEEK immersed in SB solution	in vitro	Promoted M2 polarization of macrophages	[88]
		in vivo	Reduced fibrous tissue formation and neutrophil infiltration	[88]
COOH	COOH attached to the PEEK surface using diazonium-based chemistry reactions	in vitro	Down-regulated proinflammatory TNF-α, IL-1β, and IL-6 expression and up-regulated BMP-2 expression	[89] [90]
		in vivo	Down-regulated proinflammatory gene expression	[91]
BMP2	Construction of a DOPA4 adherent layer and integration by a DBCO-azide bio-click reaction	in vitro	Promoted M2 polarization of macrophages	[92]
TiO2	TiO2 deposited on the PDA surface to form a PDA/TiO2 hybrid coating	in vitro	Reduced macrophage adhesion and decreased expression of the inflammatory factor TNF-α	[93]
	AIP	in vivo	Reduced fibrous tissue formation and promoted the mechanical association of PEEK with bone tissue	[94]
Ti	Construction of Ti coating on PEEK surfaces using plasma spraying technology	in vitro	Promoted M2 polarization of macrophages, down-regulated the expression of inflammatory factors, and regulated the osteoimmune environment	[95]
		in vivo	Reduced fibrous tissue formation	[95]
HA	Synthesis of HA powder and PEEK powder mixed materials and sulfonation	in vitro	Reduced the proportion of M1 macrophages, inhibited the expression of proinflammatory genes, and promoted the expression of anti-inflammatory genes	[96]
		in vivo	Reduced fibrous tissue formation	[97]
Nano HA/Silica	A silicone sol was sprayed onto the PEEK surface using the principle of sol-gel technology. After heat treatment, the PEEK melted and penetrated the interconnected pore structure of the coating material	in vivo	Reduced fibrous tissue formation	[98]