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The efficient cell transfection method is vital for various biomedical applications, such as the CRISPR-Cas9 technique. Current cell transfection methods, including lipofectamine, calcium phosphate co-precipitation, nucleofection, and viral infection are not equally efficient for various cells and have their disadvantages. In this study, a magnetic nanoparticle (MNP)-based method was introduced for delivering both FITC dye and a functional EGFP gene into easy-to-transfect HEK cells and difficult-to-transfect rat primary cortical neurons. The transfection efficacy could be controlled in both time-dependent and magnetic strength-dependent manner. This cell transfection method could have substantial potential for targeted drug delivery.

The present study was performed to investigate the possible role of protein kinase C (PKC) in morphine tolerance at spinal levels of rats. Intrathecal injection of 10 μg of morphine induced increases in the hindpaw withdrawal latency (HWL) to noxious thermal and mechanical stimulation in rats. After intrathecal injections of 10 μg of morphine (twice a day) lasted for 5 days, the antinociceptive effects induced by intrathecal injections of morphine decreased significantly in rats. Interestingly, we found that there were significant increases in the content of PKC in the dorsal horn of the spinal cord and the dorsal root ganglion, but not in the ventral horn of the spinal cord, in rats with morphine tolerance determined by Western blot, suggesting that PKC is involved in morphine tolerance at spinal levels of rats. Furthermore, our results demonstrated that chronic intrathecal injection of the PKC inhibitor significantly inhibited the development of morphine tolerance. Moreover, we found that the maintenance of morphine tolerance was blocked by intrathecal administration of a PKC inhibitor in rats, and the inhibitory effects of the PKC inhibitor on morphine tolerance lasted for more than two days. Taken together, the present study clearly showed that PKC is involved in morphine tolerance at the spinal level of rats and that intrathecal administration of a PKC inhibitor can block the development and maintenance of morphine tolerance.Keywords: Development of morphine tolerance, dorsal root ganglion, hindpaw withdrawal latency, maintenance of morphine tolerance, PKC, spinal cord M orphine still proves to be clinically indispensible in treating moderate to severe pain. However, the development of tolerance, antinociceptive effect produced by a given dose of morphine declined over time (1-3), largely limits its extensive application. Protein kinase C (PKC), a family of phospholipid-dependent serine/threonine kinases, has been demonstrated to play an important role in cellular signal transduction. PKC can be activated upon external stimulation of cells by various ligands including growth factors, hormones, and neurotransmitters (4-6).With the method of [ The results indicate a strong correlation between PKC and morphine tolerance, which was later confirmed by a wide range of other studies (8-11). The present study was performed to explore the role of PKC in morphine tolerance at the spinal level of rats, especial in the development and maintenance of morphine tolerance. Results and DiscussionInfluence of Morphine Tolerance on the Expression of PKC at the Spinal Level of RatsTo investigate the role of PKC in morphine tolerance at the spinal level, rats received intrathecal administration of 10 μg of morphine twice a day for 5 days to produce morphine tolerance. Another group of rats without any treatment was as the control group (n=8).As shown in Figure 1, there were significant increases in the content of PKC (n=5; F=6.34; P<0.05) in the dorsal horn of the spinal cord in rats with morphine tolerance compared wit...