Nitrogen-containing Non-thermal Plasma Modification And Its Biomedical Application

Synthetic polymer scaffolds show high potential for the repair of orthopedic and cartilage trauma.PCL is one of the most prospective biodegradable implants because of its excellent properties,such as biocompatibility and biodegradability.However,PCL still suffer from insufficient cell interaction,which is critical in capacity of cells of tissues.Non-thermal plasma technology(NTP)is a well-established gas-based technique for altering the surface chemical composition of any exposed substrate but not altering the bulk properties of material.This study proposes the use of a non-thermal nitrogen-containing plasma surface modification technology to enhance the cell-material interactions of 3D additive manufactured porous scaffolds.As amine groups are known to promote osseointegration,covalent immobilization of biomolecules,such as polysaccharide,enzymes,antibodies,collagen and DNA.In this study,a dielectric barrier discharge(DBD)plasma operated in medium to atmospheric pressure was used to modify the surface properties of PCL films and 3D porous scaffolds.Three different plasma processes(plasma activation with N2,plasma activation with NH3+He(1:9)and plasma polymerization with allylamine)were tested in parallel with the aim of incorporating N-rich functional groups,especially-NH2.A variety of discharge powers(0.4-15 W),treatment times(1-5 min),monomer flow rates(1-2 g/h)and pressures(5-100 kPa)were applied to optimize plasma effects.Water contact angle goniometry was used to initially assess the influence on the surface wettability,while XPS was used to determine the exact chemical composition of the coatings.SEM and AFM were used to characterize possible variations of structure and surface morphology.The acquired data shows that all treatments have a significant impact on wettability and are efficient in the incorporation of N-containing functional groups.For both nitrogen and ammonia plasma,the relative concentration of the different nitrogen functional groups fluctuated,whereas for the allylamine deposition,the nitrogen was always primarily incorporated as C-N.Moreover,the coating composed by poly-allylamine indicated excellent uniformity in chemical composition as a function of time once the deposition started.Furthermore,the influences of discharge pressure,treatment time,flow rate and energy density were studied in the transition to 3D scaffolds.The results of 3D scaffolds were consistent with those of the films at the same conditions,except the central part inside.Nitrogen-rich Plasmas were found to be an effective way to stimulate the incorporation of nitrogen functional groups for enhancing properties of biological applications.MC3T3 osteoblasts were seeded onto the comprehensive investigated samples and the effects on cell adhesion,viability and morphology were systematically studied.The acquired results demonstrated that all of the nitrogenous plasma treatments have a positive effect on the cell-material interactions.Of the two plasma activation approaches,NH3 plasma treatment was the best to growth of MC3T3 osteoblasts,N2 plasma followed by.For allylamine plasma deposition,a high cytotoxicity was induced in the first half of the month when coating dissolution occurred or toxic precursor allylamine remained.After 14 days of seeding when the coatings were stable,allylamine-based plasma deposition showed a better effect on improvement of the bioactivity of the PCL scaffolds.Overall,the plasma treatments including allylamine plasma coatings exhibited great prospect for cartilage tissue engineering applications after further improving the effects of scaffolds inside.Magnesium alloys possess density and elastic modulus that are closer to that of natural bones,compared with Ti alloys,stainless steels.Besides,magnesium and its alloys which are chemically active can degrade naturally in the physiological environment by corrosion,thus Mg and its alloys are potential candidates in biodegradable hard-tissue implants.However,Mg is highly chemically reactive when exposed to air or water,which then make it very susceptible to be contaminated,thus not beneficial to implanting.Compared to other available methods of removing contamination layer(thermal,chemical,et.al),non-thermal plasma in medium pressure is an effective but more environmentally friendly and economical approach.This study proposes a medium pressure(5 kPa)dielectric barrier discharge plasma approach operated in different atmospheres(argon and ammonia)to remove contamination on pure Mg discs.Besides a cytotoxicity assay performed by the live/dead analysis,also the effect of the treatments on the degradation rate,pH and osmolality in the degradation process were measured.Results reveal that both plasmas remove more than 40%of the carbonaceous contaminations while introducing surface oxygen(and nitrogen)containing functionalities.Nevertheless,grinding only removes 34%of the initial surface carbon.Despite being the most efficient in eliminating the organic layer,the chemical treatment leads to an excessive surface oxidation.In vitro tests involving perivascular cells reveal that plasma-treated samples outperform their ground and chemically cleaned counterparts in terms of cell-surface affinity as more spread out cells with significantly bigger areas are detected,suggestive of a robust cell attachment.Moreover,plasma do not alter the degradation rate of Mg discs,thus providing a striking insight for their application in tissue engineering.Overall,one can conclude that the eco-friendly and economical sub-atmospheric plasma is an effective alternative synergistically cleaning and improving the cyto-compatibility of Mg surfaces.