It was necessary to study the bonding mechanism of poly(D,L-lactide) (PDLLA) and hydroxyapatite (HA) nanoparticles because of their increasing application in medical fields. In this paper, hydrogen bonding between PDLLA and HA in PDLLA/HA nanocomposites was first investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Structural morphology and glass transition temperature (T g ) of the nanocomposites showed that there was a close interaction between polymer matrix and inorganic nanoparticls. The results from FTIR and XPS indicated that the hydrogen bonding between the CdO in PDLLA and the surface PsOH groups of HA nanocrystalline was formed indeed. Shape memory properties were improved, which further implied the existence of hydrogen bonding in these nanocomposites. Thus, we designed a schematic model of the hydrogen bonding on the base of the experimental results. It can clearly explain the interaction mechanism of polymeric phases and inorganic phase in nanocomposites.

Purinergic signaling has been implicated in the regulation of many cellular processes. A high concentration of ATP has been observed in the tumor microenvironment, suggesting a possible role of extracellular ATP in tumor progression. The P2X7 receptor, which belongs to the ligand-gated ion channel receptor family, is involved in tumor development and metastasis. In the present study, we found that extracellular ATP stimulated the invasion and migration of human T47D breast cancer cells, in a dose-dependent manner. BzATP (ATP analogue), but not ADP, also promoted invasion and migration. We further found that the P2X7 receptor was highly expressed in the T47D cells. After knockdown of the P2X7 receptor, ATP-stimulated invasion and migration were markedly inhibited. Moreover, activation of the P2X7 receptor by ATP downregulated the protein level of E-cadherin and upregulated the production of MMP-13. In addition, ATP time-dependently induced the activation of AKT via the P2X7 receptor, and the AKT pathway was required for the ATP-mediated invasion and migration. Taken together, our results revealed that activation of the P2X7 receptor by ATP promotes breast cancer cell invasion and migration, possibly via activation of the AKT pathway and regulation of E-cadherin and MMP-13 expression. Therefore, the P2X7 receptor may be a useful therapeutic target for the treatment of breast cancer.

This paper reports a kind of biodegradable nanocomposite which can show an excellent shape-memory property in hot water or in an alternating magnetic field with f = 20 kH and H = 6.8 kA m(-1). The nanocomposite is composed of crosslinked poly(epsilon-caprolactone) (c-PCL) and Fe(3)O(4) nanoparticles. The crosslinking reaction in PCL with linear molecular structure was realized using benzoyl peroxide (BPO) as an initiator. The biocompatible Fe(3)O(4) magnetite nanoparticles with an average size of 10 nm were synthesized according to a chemical coprecipitation method. The initial results from c-PCL showed crosslinking modification had brought about a large enhancement in shape-memory effect for PCL. Then a series of composites made of Fe(3)O(4) nanoparticles and c-PCL were prepared and their morphological properties, mechanical properties, thermodynamic properties and shape-memory effect were investigated in succession. Significantly, the photos of the shape-memory process confirmed the anticipatory magnetically responsive shape-recovery effect of the nanocomposites because inductive heat from Fe(3)O(4) can be utilized to actuate the c-PCL vivification from their frozen temporary shape. All the results imply a very feasible method to fabricate shape-memory PCL-based nanocomposites since just a simple modification is required. Additionally, this modification would endow an excellent shape-memory effect to all other kinds of polymers so that they could broadly serve in various fields, especially in medicine.

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