Amino modified polyether ether ketone surface and its osteoblastic compatibility

This article first uses sodium borohydride to reduce the carbonyl groups on the surface of polyether ether ketone to hydroxyl groups, obtaining hydroxylated PEEK rods. Then, 3-aminopropyltriethoxysilane reacts with them to introduce amino (- NH2) to the surface of PEEK to improve its cell compatibility. The surface chemically treated PEEK was characterized by X-ray photoelectron spectroscopy and mechanical properties testing, while the cell compatibility of the surface amino modified PEEK was evaluated using MC3T3-E1 osteoblasts. The results showed that sodium borohydride successfully reduced the carbonyl groups on the surface of PEEK to hydroxyl groups, and - NH2 was successfully introduced to the surface of PEEK; There was no significant change in the tensile and bending strength of PEEK plates and rods before and after surface chemical treatment; Compared with unmodified PEEK surface, NH2 modified PEEK surface can significantly promote the adhesion, spreading, and proliferation of osteoblasts.

1. Research Purpose

PEEK is formed by a benzene ring connected in the opposite position through ketone and ether bonds. Its resonance stable chemical structure causes orbital electrons to delocalize throughout the entire molecular chain, thus PEEK has extremely strong chemical stability. Studies have shown that introducing certain chemical groups on the surface of materials, such as carboxyl (- COOH), hydroxyl (- OH), amino (- NH2), sulfonic acid (- SO3H), etc., can promote cell adhesion, spreading, and proliferation. Among these functional groups, the surface modified with - NH2 is more capable of stimulating cell osteogenic differentiation. Therefore, this article utilizes silane coupling agents with amino groups at the end to react with the hydroxyl groups generated after reduction on PEEK, in order to introduce - NH2 on the surface of PEEK and improve its cell compatibility.

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Add 5% volume concentration of APTES anhydrous toluene solution to a dry circular bottom flask with reflux condensation device. Immerse the P-PEEK-OH24 sample in a solution and react for 16 hours under nitrogen protection at 60 ° C (as shown in Figure 1). Then, sequentially clean with toluene, methanol, and distilled water for 20 minutes. After vacuum drying at 110 ℃ for 0.5 hours, store in a dryer for future use. Surface amino modified PEEK, labeled PEEK-NH2.

3. Experimental results

3.1 Analysis of Surface Hydroxylation Pretreatment of PEEK

The relative content and O/C ratio of different elements on the surface of each PEEK sample

The XPS spectra of the surfaces of P-PEEK-OH24 and P-PEEK-OH48 (not listed) are similar to those of P-PEEK. Table 1 shows the changes in the relative content of various elements on the surface of PEEK. From Figure 2 and Table 1, it can be seen that after the reduction of carbonyl groups on the surface of PEEK, the types of elements on its surface remain unchanged, but the relative contents of each element are different, indicating a change in the surface chemical environment.

P-PEEK and P-PEEK-OH24 have C=O peaks at 287.2 eV, and the C=O peak area of P-PEEK is significantly larger than that of P-PEEK-OH24, indicating that the relative content of C=O in the latter is lower than that of the former (Table 2); In the C1s spectrum of P-PEEK-OH48, the peak at 287.2 eV completely disappeared, indicating the absence of C=O within the depth range detected by XPS (0-10 nm). This is because as the reaction progresses, C=O on the surface of PEEK is gradually reduced. When the reaction time reaches 48 hours, C=O is completely reduced. The O1s spectrum also confirms this conclusion. The peak located at 531.5 eV in the O1s spectrum belongs to the O=C on the surface of P-PEEK and P-PEEK-OH24. The peak area of the former is larger than that of the latter, and a new O-H peak appears at 532.2 eV; When the reaction time was 48 hours, the O=C peak in the O1s spectrum of P-PEEK-OH48 completely disappeared, indicating that the O=C component was gradually reduced and the relative content gradually decreased with the reaction (Table 2). Finally, the O=C within the depth range of XPS detection was completely reduced to O-H.

Successfully introduced to the surface of PEEK, Figure 5 shows that the thickness of the silane film formed on the surface of PEEK is within the detection depth range of XPS, which indirectly indicates a change in the chemical state of the PEEK surface.

3.3 Evaluation of in vitro cell compatibility

The optical density value of P-PEEK sample is lower than that of PEEK-NH2 sample (P<0.05), indicating that PEEK-NH2 has better osteoblast adhesion ability compared to P-PEEK.

It can be seen that the unmodified PEEK has fewer surface cells, a spherical shape, and fewer protruding pseudopodia (Figure 8a); The number of cells on the surface of PEEK-NH2 increases, mostly presenting a flat morphology with good spreading status and more protruding pseudopodia (Figure 8b). This indicates that NH2 plays a very beneficial role in the adhesion and spreading of osteoblasts, providing favorable conditions for the subsequent proliferation of osteoblasts.

4. Conclusion

Successfully reduced the carbonyl groups on the surface of PEEK to hydroxyl groups using NaBH4; The reaction between APTES and hydroxylated PEEK successfully introduced - NH2 onto the surface of PEEK.

The mechanical performance test results indicate that surface chemical modification does not affect the excellent mechanical properties of PEEK. The results of in vitro cell compatibility experiments showed that NH2 significantly improved the adhesion, spreading, and proliferation of MC3T3-E1 osteoblasts on the surface of PEEK.

Changzhou Buick Machinery Manufacturing Co., Ltd. focuses on the production and processing of special engineering plastic products such as polyether ether ketone (PEEK), PI, PPS, and PAI. PEEK products are widely used in various industries such as analytical instruments, electronic semiconductor industry, automotive industry, food packaging machinery industry, textile printing and dyeing machinery, due to their excellent comprehensive performance such as high temperature resistance, self-lubrication, wear resistance, high strength, and corrosion resistance. Our company has accumulated rich experience in the processing and manufacturing of special engineering plastic products, including product injection molding, turning and milling processing, precision engraving machine processing, etc. In addition to PEEK screws, PEEK rods, PEEK plates, PEEK joints, PEEK gears and other industry standard parts, our company can also customize and process according to customer needs (providing samples or drawings). We sincerely hope to cooperate with you.