The adsorption of biomolecules to the surface of nanoparticles (NPs) following administration into biological environments is widely recognized. In particular, the "protein corona" is well understood in terms of formation kinetics and impact upon the biological interactions of NPs. Its presence is an essential consideration in the design of therapeutic NPs. In the present study, the protein coronas of six polymeric nanoparticles of prospective therapeutic use were investigated. These included three colloidal NPs-soft core-multishell (CMS) NPs, plus solid cationic Eudragit RS (EGRS), and anionic ethyl cellulose (EC) nanoparticles-and three nanogels (NGs)-thermoresponsive dendritic-polyglycerol (dPG) nanogels (NGs) and two amino-functionalized dPG-NGs. Following incubation with human plasma, protein coronas were characterized and their biological interactions compared with pristine NPs. All NPs demonstrated protein adsorption and increased hydrodynamic diameters, although the solid EGRS and EC NPs bound notably more protein than the other tested particles. Shifts toward moderately negative surface charges were also observed for all corona bearing NPs, despite varied zeta potentials in their pristine states. While the uptake and cellular adhesion of the colloidal NPs in primary human keratinocytes and human umbilical vein endothelial cells were significantly decreased when bearing the protein corona, no obvious impact was seen in the NGs. By contrast, corona bearing NGs induced marked increases in cytokine release from primary human macrophages not seen with corona bearing colloidal NPs. Despite this, no apparent enhancement to in vitro toxicity was noted. Finally, drug release from EGRS and EC NPs was assessed, where a decrease was seen in the EGRS NPs alone. Together these results provide a direct comparison of the physical and biological impact the protein corona has on NPs of widely varied character and in particular highlights a distinction between the corona's effects on NGs and colloidal NPs.

Oral mucositis is one of the most common side effects of chemoradiation regimens and manifestation can be dose-limiting for the therapy, can impair the patient's nutritional condition and quality of life due to severe pain. The therapeutic options are limited; often only an alleviation of the symptoms such as pain reduction by using systemic opioids is possible. Stimulating opioid receptors on peripheral neurons and dermal tissue, potent analgesic effects are induced e.g. in skin grafted patients. Advantageous effects on the cell migration and, thus, on the wound healing process are described, too. In this study, we investigated whether opioid receptors are also expressed on oral epithelial cells and if morphine can modulate their cell migration behavior. The expression of the opioid receptors MOR, DOR and KOR on primary human oral epithelial cells was verified. Furthermore, a significantly accelerated cell migration was observed following incubation with morphine. The effect even slightly exceeded the cell migration stimulating effect of TGF-ß: After 14 h of morphine treatment about 86% of the wound area was closed, whereas TGF-ß application resulted in a closed wound area of 80%. With respect to morphine stimulated cell migration we demonstrate that DOR plays a key role and we show the involvement of the MAPK members Erk 1/2 and p38 using Western blot analysis.Further studies in more complex systems in vitro and in vivo are required. Nevertheless, these findings might open up a new therapeutic option for the treatment of oral mucositis.

Oral mucositis is a common side effect of chemotherapy and radiation therapy accompanied with acute inflammation and ulceration of the oral mucosa. Opioids can improve the wound healing of dermal and oral tissue when applied locally. The aim of this study was to investigate if morphine exhibits cytoprotective effects on oral epithelial cells postirradiation. Hence, oral epithelial cells were exposed to increasing doses (3-30 Gy) of ionization radiation. We assessed the effects of the radiation on cell viability, proinflammatory cytokine release (interleukin [IL]-1α, IL-6), and matrix metalloproteinase (MMP-1, -8, and -9) expression. As expected, radiation significantly impaired cell viability and morphology and resulted in enhanced IL release. However, morphine-treated cells consistently showed higher cell viability postirradiation: 9.19 ± 1.16% after 24 hours and 7.45 ± 0.93% after 48 hours compared with the control. In terms of proinflammatory cytokines, the release of IL-1α and IL-6 was significantly reduced, too, being most pronounced at 48 hours postradiation. Additionally, we observed a significant reduction of MMP-1 and especially MMP-9 expression in morphine-treated cells. The results clearly indicate anti-inflammatory as well as cytoprotective effects of morphine on irradiated oral epithelial cells. Interestingly, the protective effects of morphine are not related to a decrease in cell apoptosis or necrosis. Before final conclusions can be drawn, further studies in more complex systems in vitro and in vivo are required. Nevertheless, these findings further underline the high potential of opioids for the treatment of topical wounds and inflammatory conditions.