Nematic-to-Isotropic Phase Transition in Poly(L-Lactide) with Addition of Cyclodextrin during Abiotic Degradation Study.

Poly(L-lactide) is capable of self-assembly into a nematic mesophase under the influence of temperature and mechanical stresses. Therefore, subsequent poly(L-lactide) films were obtained and characterized, showing nematic liquid crystal properties both before and after degradation. Herein, we present that, by introducing ß-cyclodextrin into the polymer matrix, it is possible to obtain a chiral nematic mesophase during pressing, regardless of temperature and time. The obtained poly(L-lactide) films exhibiting liquid crystal properties were subjected to degradation tests and the influence of degradation on these properties was determined. Thermotropic phase behavior was investigated using polarized optical microscopy, X-ray diffraction, and differential scanning calorimetry. The degradation process demonstrated an influence on the liquid crystal properties of pressed polymer films. The colored planar texture of the chiral nematic mesophase, which was not observed prior to degradation in films without the addition of ß-cyclodextrin, appeared after incubation in water as a result of the entrapment of degradation products in the polymer matrix. These unusual tailor-made properties, obtained in liquid crystals in (bio)degradable polymers using a simple method, demonstrate the potential for advanced photonic applications.

Hydroxyapatite Obtained via the Wet Precipitation Method and PVP/PVA Matrix as Components of Polymer-Ceramic Composites for Biomedical Applications.

The aspect of drug delivery is significant in many biomedical subareas including tissue engineering. Many studies are being performed to develop composites with application potential for bone tissue regeneration which at the same provide adequate conditions for osteointegration and deliver the active substance conducive to the healing process. Hydroxyapatite shows a great potential in this field due to its osteoinductive and osteoconductive properties. In the paper, hydroxyapatite synthesis via the wet precipitation method and its further use as a ceramic phase of polymer-ceramic composites based on PVP/PVA have been presented. Firstly, the sedimentation rate of hydroxyapatite in PVP solutions has been determined, which allowed us to select a 15% PVP solution (sedimentation rate was 0.0292 mm/min) as adequate for preparation of homogenous reaction mixture treated subsequently with UV radiation. Both FT-IR spectroscopy and EDS analysis allowed us to confirm the presence of both polymer and ceramic phase in composites. Materials containing hydroxyapatite showed corrugated and well-developed surface. Composites exhibited swelling properties (hydroxyapatite reduced this property by 25%) in simulated physiological fluids, which make them useful in drug delivery (swelling proceeds parallel to the drug release). The short synthesis time, possibility of preparation of composites with desired shapes and sizes and determined physicochemical properties make the composites very promising for biomedical purposes.

Poly(l-Lactide) Liquid Crystals with Tailor-Made Properties Toward a Specific Nematic Mesophase Texture.

This paper presents the liquid crystal (LC) properties of poly(l-lactide) (PLLA). Mesophase behavior is investigated using polarized optical microscopy, X-ray diffraction, and differential scanning calorimetry. The performed analyses confirm that pressed PLLA films exhibit the unique capability of self-assembling into a nematic mesophase under the influence of mechanical pressure, temperature, and time. It was originally demonstrated that the chiral nematic mesophase can be obtained by introducing fine powders into the polymer. Based on the research conducted, it was proved that the pressed PLLA films have a chiral nematic mesophase with a nematic-to-isotropic phase transition and a large mesophase stability range overlapping the temperature of the human body, which can persist for years at ambient temperature. The obtained films show tailor-made properties toward a nematic mesophase with a specific texture, including colored planar texture of the chiral nematic mesophase and blue-phase (BP) LC texture. The BP, described for the first time in plain PLLA, occurred over a wider than usual temperature range of stability between isotropic and chiral nematic thermotropic phases (ΔT ≈ 9 °C), which is an advantage of the obtained polymer material, in addition to ease of preparation. This opens up new prospects for advanced photonic green applications.

Evaluation of the impact of pH of the reaction mixture, type of the stirring, and the reagents' concentration in the wet precipitation method on physicochemical properties of hydroxyapatite so as to enhance its biomedical application potential.

Hydroxyapatite (HAp) constitutes a significant inorganic compound which due to its osteoinductivity, osteoconductivity as well as the ability to promote bone growth and regeneration is widely applied in development of biomaterials designed for bone tissue engineering. In this work, various synthesis methodologies of HAp based on the wet precipitation technique were applied, and the impact of pH of the reaction mixture, the concentration of individual reagents as well as the type of stirring applied (mechanical/magnetic) on the properties of final powders was discussed. Spectroscopic methods (Fourier transform infrared, Raman) and X-ray diffraction allowed to verify the synthesis parameters leading to obtaining calcium phosphate with 96% HAp in phase which indicated higher homogeneity of obtained powder (93.4%) than commercial HAp. Powders' morphology was evaluated using microscopic techniques while specific surface area was determined via Brunauer-Emmett-Teller analysis. Particle size distribution, porosity of powders, and stability of HAp suspensions were also characterized. It was proved that synthesis at pH = 11.0 using mechanical stirring resulted in calcium phosphate with a high phase homogeneity and homogeneous pore size distribution (6-20 nm). Moreover, obtained HAp powder showed 71.8% more specific surface area than commercial material-that is, 110 m3 /g for synthetic HAp and 64 m3 /g in the case of commercial powder-which, in turn, is significant in terms of its potential application as carrier of active substances. Thus it was demonstrated that by applying appropriate conditions of HAp synthesis it is possible to obtain powder with properties enhancing its application potential for medical purposes.

The Influence of Hydrophobic Blocks of PEO-Containing Copolymers on Glyceryl Monooleate Lyotropic Liquid Crystalline Nanoparticles for Drug Delivery.

The investigation of properties of amphiphilic block copolymers as stabilizers for non-lamellar lyotropic liquid crystalline nanoparticles represents a fundamental issue for the formation, stability and upgraded functionality of these nanosystems. The aim of this work is to use amphiphilic block copolymers, not studied before, as stabilizers of glyceryl monooleate 1-(cis-9-octadecenoyl)-rac-glycerol (GMO) colloidal dispersions. Nanosystems were prepared with the use of poly(ethylene oxide)-b-poly(lactic acid) (PEO-b-PLA) and poly(ethylene oxide)-b-poly(5-methyl-5-ethyloxycarbonyl-1,3-dioxan-2-one) (PEO-b-PMEC) block copolymers. Different GMO:polymer molar ratios lead to formulation of nanoparticles with different size and internal organization, depending on the type of hydrophobic block. Resveratrol was loaded into the nanosystems as a model hydrophobic drug. The physicochemical and morphological characteristics of the prepared nanosystems were investigated by dynamic light scattering (DLS), cryogenic transmission electron microscopy (cryo-TEM), fast Fourier transform (FFT) analysis and X-ray diffraction (XRD). The studies allowed the description of the lyotropic liquid crystalline nanoparticles and evaluation of impact of copolymer composition on these nanosystems. The structures formed in GMO:block copolymer colloidal dispersions were compared with those discussed previously. The investigations broaden the toolbox of polymeric stabilizers for the development of this type of hybrid polymer/lipid nanostructures.

Physicochemical Characteristics of Chitosan-Based Hydrogels Containing Albumin Particles and Aloe vera Juice as Transdermal Systems Functionalized in the Viewpoint of Potential Biomedical Applications.

In recent years, many investigations on the development of innovative dressing materials with potential applications, e.g., for cytostatics delivery, have been performed. One of the most promising carriers is albumin, which tends to accumulate near cancer cells. Here, chitosan-based hydrogels containing albumin spheres and Aloe vera juice, designed for the treatment of skin cancers or burn wounds resulting from radiotherapy, were developed. The presence of albumin in hydrogel matrices was confirmed via Fourier transform infrared (FT-IR) and Raman spectroscopy. Albumin spheres were clearly visible in microscopic images. It was proved that the introduction of albumin into hydrogels resulted in their increased resistance to the tensile load, i.e., approximately 30% more force was needed to break such materials. Modified hydrogels showed approximately 10% more swelling ability. All hydrogels were characterized by hydrophilicity (contact angles were <90°) which may support the regeneration of epithelial cells and non-cytotoxicity towards murine fibroblasts L929 and released Aloe vera juice more effectively in an acidic environment than in a neutral one wherein spheres introduced into the hydrogel matrix extended the release time. Thus, the developed materials, due to their chemical composition and physicochemical properties, constitute promising materials with great application potential for biomedical purposes.

Electrospun paclitaxel delivery system based on PGCL/PLGA in local therapy combined with brachytherapy.

The local administration of different drugs in anticancer therapy continue to attract attention. Thus, the idea of local delivery of cytostatics from nonwoven-structured polyesters seems to be highly desirable. It could reduce systemic drug levels and provide high local concentration of the chemotherapeutics at the tumor site and contribute to enhance the efficiency of the anticancer therapy. Poly(glycolide-ɛ-caprolactone) (PGCL) and poly(D,L-lactide-co-glycolide) (PLGA) synthesized with zirconium-based initiator have been used to prepare electrospun, drug-eluting patches since they possess very good fiber-forming ability. Well-known chemotherapeutic drug-paclitaxel has been loaded into fibrous structure as a model anticancer agent in order to obtain drug delivery systems for local administration. The drug dose in obtained nonwovens might be regulated by the thickness and total area of the implanted patches. Electrospinning of PGCL/PLGA blend allowed to obtain soft and flexible implantable materials. Flexibility has been important factor since it ensures convenient use when covering a tumor or filling a resection cavity. The effectiveness of designed nonwovens presented in the study has been tested in vivo on mouse model of breast cancer. The growth of the tumors was slowed down during in vivo study in comparison with drug-free nonwovens- The volume of the tumor was 40% lower. Drug-loaded electrospun systems implanted locally to the tumor site was further combined with brachytherapy which improved the effectiveness of the therapy in about 18%. Detailed analysis of the nonwovens before and during degradation process has been performed by means of Scanning Electron Microscopy, Differential Scanning Calorimetry, Nuclear Magnetic Resonance, Gel Permeation Chromatography, X-ray Diffraction. The molar mass changes of the nonwoven were quite rapid contrary to changes of comonomer unit content, thermal properties and morphology of the fiber.

Facile production of ultra-fine silicon nanoparticles.

A facile procedure for the synthesis of ultra-fine silicon nanoparticles without the need for a Schlenk vacuum line is presented. The process consists of the production of a (HSiO1.5) n sol-gel precursor based on the polycondensation of low-cost trichlorosilane (HSiCl3), followed by its annealing and etching. The obtained materials were thoroughly characterized after each preparation step by electron microscopy, Fourier transform and Raman spectroscopy, X-ray dispersion spectroscopy, diffraction methods and photoluminescence spectroscopy. The data confirm the formation of ultra-fine silicon nanoparticles with controllable average diameters between 1 and 5 nm depending on the etching time.