Surface Modification And Biocompatibility Evaluation Of Acrylate Intraocular Lenses

Up to now,it is well known that surgery with the extraction of natural opacifiedcrystalline lens and then the implantation of IOLs is the only proven therapy for cataract.Biocompatibility is a critical guideline for the selection of commercial IOLs in cataractsurgery.With the prevalence of the modern small incision cataract surgery,thefoldable hydrophobic acrylate IOLs have become the most preferred one by thesurgeons.In terms of biocompatibility,the greatest advantage of these IOLs is theirprominent performance in the PCO prevention,as the sharp-edged and the inherentbioadhesive posterior surface can effectively inhibit the migration and proliferation ofLECs.However,compared with the hydrophilic acrylate IOLs,higher rates of theforeign-body reaction and ACO were also reported for the hydrophobic acrylate IOLs,both of which are related to the anterior IOL surface.We propose that surfacemodification should be an avenue to improve the surface hydrophilicity and thebiocompatibility of the hydrophobic acrylate IOLs,without change in the optical andmechanical properties of the bulk.Two new techniques,which are dielectric barrierdischarge (DBD) plasma at atmospheric pressure and electrostatic layer-by-layerself-assembly,are used for the surface mofication of acrylate IOL.They can work in a flexible,reliable,environmentally friendly,less expensive and continuous way andfavor the industrial production.To evaluate the physicochemical properties of plasma-treated IOL surfaces,changesin chemical composition,morphology and hydrophilicity were comprehensivelyevaluated by X-ray photoelectron spectroscopy (XPS),field emission scanning electronmicroscopy (FESEM),atomic force microscopy (AFM) and water contact angle (WCA)measurements.Meanwhile,the surface biocompatibility of the untreated andplasma-treated IOLs was compared by the adhesion behaviors ofplatelets,macrophagesand lens epithelial cells (LECs) in vitro.The density of adhered cells was countedunder the optical microscopy and the changes in cell morphology were also observed byenvironmental scanning electron microscope (ESEM).Further,LECs death andapoptosis were evaluated by acridine orange (AO) / propidium iodide (PI) staining.First,DBD plasma at atmospheric pressure (argon as the discharge gas) was carriedout to modify the acrylate IOLs surfaces.After DBD plasma treatment,thehydrophilicity of the IOL surface is obviously improved.The changes in WCA withtreatment time can be attributed to both the introduction of oxygen-/nitrogen-containingpolar groups and the increase of surface roughness induced by plasma etching effect.The existence of low molecular weight oxidized material (LMWOM) is proved on theplasma-treated IOL which is caused by the chain scission effect of plasma treatment.The plasma-treated IOLs resist the adhesion of platelets and macrophages significantly.The LECs spreading and proliferation are postponed on the IOLs plasma-treated formore than 180 s,with a well maintained epithelial phenotype of LECs.The IOLbiocompatibility is improved after the DBD plasma treatment.Second,based on the DBD plasma treatment,the polyelectrolyte multilayered films(PEMs) were constructed by the alternate deposition of poly(L-lysine) (PLL) andhyaluronic acid (HA) onto the surface of the acrylate IOLs.XPS analysis confirmedthe immobilization of polyelectrolyte multilayers (PEMs) on the IOLs surfaces. FESEM results showed no change on the IOLs surfaces after the modification.AFMshowed that the polyelectrolytes were uniformly and smoothly deposited,and noobvious changes in the surface roughness were observed.The hydrophilicity wassignificantly improved,and WCA oscillated between the PLL and HA layers,verifyingthe process of alternate deposition.Further,in vitro cell adhesion tests revealed thatthe adhesion and spreading of the platelets,macrophages on the PEMs-modified IOLwere both apparently suppressed.The adhesion,spreading and proliferation of LECswere also suppressed because of the cytostatic effect of PEMs rather than cytotoxicity.Both techniques of DBD plasma at atmospheric pressure and electrostaticlayer-by-layer self-assembly are effective to modify the hydrophobic acrylate IOLsurfaces.The construction of PLL/HA PEMs seems to excel in the improvement ofsurface hydrophilicity and the suppression of cell adhesion.We speculate that lessforeign-body reaction and slower incidence of anterior capsule opacification (ACO)could be expected after the implantation of surface-mofied IOL.