Nanocrystallite-liquid phase transition in porous matrices with chemically functionalized surfaces.

Nanocrystallite-liquid phase transitions are studied for 1-octadecene confined in the pores of chemically functionalized silica gels. These silica gels possess similar fractal geometries of the pore system but differ in chemical termination of the surface, specific surface area (F) and pore volume (V). Linear dependencies of the melting temperature and specific melting heat on the F/V ratio are found for a series of silica gels with identical surface termination. A thermodynamic model based on experimental data is established, which explains the observed shift of the phase transition parameters for porous matrices with different surface chemistries. In addition, this model allows evaluation of actual changes in nanocrystallite density, surface tension and entropy upon melting.

Interpenetrating Polymer Networks of Polyacrylamide with Polyacrylic and Polymethacrylic Acids and Their Application for Modified Drug Delivery - a Flash Review.

Polyacrylic and polymethacrylic acids, in combination with polymers such as polyacrylamide, provide the ability for controlled and sustained drug delivery since they represent pHand temperature responsiveness. In addition, the synthesis techniques can be used to develop a higher level of supramolecular structures as the interpenetrating polymer networks - as bulk hydrogels or micro-/nanogels. They can provide the opportunity to organize and build up state-ofthe- art carriers for different types of drugs, thus providing the ability to control their loading capacity and drug release performance. This flash review aims to summarize the efforts for synthesizing such interpenetrating polymer networks and their properties and to demonstrate the authors' contributions to this field.

Interpenetrating Polymer Networks of Poly(2-hydroxyethyl methacrylate) and Poly(N, N-dimethylacrylamide) as Potential Systems for Dermal Delivery of Dexamethasone Phosphate.

In this study, a series of novel poly(2-hydroxyethyl methacrylate) (PHEMA)/poly(N,N'-dimethylacrylamide) (PDMAM) interpenetrating polymer networks (IPNs) were synthesized and studied as potential drug delivery systems of dexamethasone sodium phosphate (DXP) for dermal application. The IPN composition allows for control over its swelling ability as the incorporation of the highly hydrophilic PDMAM increases more than twice the IPN swelling ratio as compared to the PHEMA single networks, namely from ~0.5 to ~1.1. The increased swelling ratio of the IPNs results in an increased entrapment efficiency up to ~30% as well as an increased drug loading capacity of DXP up to 4.5%. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) show the formation of a solid dispersion between the drug DXP and the polymer (IPNs) matrix. Energy-dispersive X-ray (EDX) spectroscopy shows an even distribution of DXP within the IPN structure. The DXP release follows Fickian diffusion with ~70% of DXP released in 24 h. This study demonstrates the potential of the newly developed IPNs for the dermal delivery of DXP.

Poly(acrylic acid-co-acrylamide)/Polyacrylamide pIPNs/Magnetite Composite Hydrogels: Synthesis and Characterization.

Novel composite hydrogels based on poly(acrylic acid-co-acrylamide)/polyacrylamide pseudo-interpenetrating polymer networks (pIPNs) and magnetite were prepared via in situ precipitation of Fe3+/Fe2+ ions within the hydrogel structure. The magnetite formation was confirmed by X-ray diffraction, and the size of the magnetite crystallites was shown to depend on the hydrogel composition: the crystallinity of the magnetite particles increased in line with PAAM content within the composition of the pIPNs. The Fourier transform infrared spectroscopy revealed an interaction between the hydrogel matrix, via the carboxylic groups of polyacrylic acid, and Fe ions, which strongly influenced the formation of the magnetite articles. The composites' thermal properties, examined using differential scanning calorimetry (DSC), show an increase in the glass transition temperature of the obtained composites, which depends on the PAA/PAAM copolymer ratio in the pIPNs' composition. Moreover, the composite hydrogels exhibit pH and ionic strength responsiveness as well as superparamagnetic properties. The study revealed the potential of pIPNs as matrices for controlled inorganic particle deposition as a viable method for the production of polymer nanocomposites.

Polycarboxy/Sulfo Betaine-Calcium Phosphate Hybrid Materials with a Remineralization Potential.

Biomacromolecules control mineral formation during the biomineralization process, but the effects of the organic components' functionality on the type of mineral phase is still unclear. The biomimetic precipitation of calcium phosphates in a physiological medium containing either polycarboxybetaine (PCB) or polysulfobetaine (PSB) was investigated in this study. Amorphous calcium phosphate (ACP) or a mixture of octacalcium phosphate (OCP) and dicalcium phosphate dihydrate (DCPD) in different ratios were identified depending on the sequence of initial solution mixing and on the type of the negative functional group of the polymer used. The more acidic character of the sulfo group in PSB than the carboxy one in PCB determines the dominance of the acidic solid phases, namely, an acidic amorphous phase or DCPD. In the presence of PCB, the formation of ACP with acicular particles arranged in bundles with the same orientation was observed. A preliminary study on the remineralization potential of the hybrid material with the participation of PSB and a mixture of OCP and DCPD did not show an increase in enamel density, contrary to the materials based on PCB and ACP. Moreover, the latter showed the creation of a newly formed crystal layer similar to that of the underlying enamel. This defines PCB/ACP as a promising material for enamel remineralization.

Bioinspired Remineralization of Artificial Caries Lesions Using PDMAEMA/Carbomer/Calcium Phosphates Hybrid Microgels.

Dental caries remains one of the most prevalent bacterium-caused chronic diseases affecting both adults and children worldwide. The development of new materials for enhancing its remineralization is one of the most promising approaches in the field of advanced dental materials as well as one of the main challenges in non-invasive dentistry. The aim of the present study is to develop novel hybrid materials based on (PDMAEMA)/Carbomer 940 microgels with in situ deposited calcium phosphates (CaP) and to reveal their potential as a remineralization system for artificial caries lesions. To this purpose, novel PDMAEMA/Carbomer 940 microgels were obtained and their core-shell structure was revealed by transmission electron microscopy (TEM). They were successfully used as a matrix for in situ calcium phosphate deposition, thus giving rise to novel hybrid microgels. The calcium phosphate phases formed during the deposition process were studied by X-ray diffraction and infrared spectroscopy, however, due to their highly amorphous nature, the nuclear magnetic resonance (NMR) was the method that was able to provide reliable information about the formed inorganic phases. The novel hybrid microgels were used for remineralization of artificial caries lesions in order to prove their ability to initiate their remineralization. The remineralization process was followed by scanning electron microscopy (SEM), X-ray diffraction, infrared and Raman spectroscopies and all these methods confirmed the successful enamel rod remineralization upon the novel hybrid microgel application. Thus, the study confirmed that novel hybrid microgels, which could ensure a constant supply of calcium and phosphate ions, are a viable solution for early caries treatment.