Biodegradable Polymersomes with Structure Inherent Fluorescence and Targeting Capacity for Enhanced Photo-Dynamic Therapy.

Biodegradable nanostructures displaying aggregation-induced emission (AIE) are desirable from a biomedical point of view, due to the advantageous features of loading capacity, emission brightness, and fluorescence stability. Herein, biodegradable polymers comprising poly (ethylene glycol)-block-poly(caprolactone-gradient-trimethylene carbonate) (PEG-P(CLgTMC)), with tetraphenylethylene pyridinium-TMC (PAIE) side chains have been developed, which self-assembled into well-defined polymersomes. The resultant AIEgenic polymersomes are intrinsically fluorescent delivery vehicles. The presence of the pyridinium moiety endows the polymersomes with mitochondrial targeting ability, which improves the efficiency of co-encapsulated photosensitizers and improves therapeutic index against cancer cells both in vitro and in vivo. This contribution showcases the ability to engineer AIEgenic polymersomes with structure inherent fluorescence and targeting capacity for enhanced photodynamic therapy.

Surface Modification of PLLA, PTFE and PVDF with Extreme Ultraviolet (EUV) to Enhance Cell Adhesion.

Recently, extreme ultraviolet (EUV) radiation has been increasingly used to modify polymers. Properties such as the extremely short absorption lengths in polymers and the very strong interaction of EUV photons with materials may play a key role in achieving new biomaterials. The purpose of the study was to examine the impact of EUV radiation on cell adhesion to the surface of modified polymers that are widely used in medicine: poly(tetrafluoroethylene) (PTFE), poly (vinylidene fluoride) (PVDF), and poly-L-(lactic acid) (PLLA). After EUV surface modification, which has been performed using a home-made laboratory system, changes in surface wettability, morphology, chemical composition and cell adhesion polymers were analyzed. For each of the three polymers, the EUV radiation differently effects the process of endothelial cell adhesion, dependent of the parameters applied in the modification process. In the case of PVDF and PTFE, higher cell number and cellular coverage were obtained after EUV radiation with oxygen. In the case of PLLA, better results were obtained for EUV modification with nitrogen. For all three polymers tested, significant improvements in endothelial cell adhesion after EUV modification have been demonstrated.

Impact of sterilization by electron beam, gamma radiation and X-rays on electrospun poly-(ε-caprolactone) fiber mats.

Biodegradable polymers such as polycaprolactone (PCL) are increasingly used for electrospinning substrates for tissue engineering. These materials offer great advantages such as biocompatibility and good mechanical properties. However, in order to be approved for human implantation they have to be sterilized. The impact of commonly used irradiation sterilization methods on electrospun PCL fiber mats was investigated systematically. Electron beam (ß-irradiation), gamma and X-ray irradiation with two different doses (25 and 33 kGy) were investigated. To determine the impact on the fiber mats, mechanical, chemical, thermal properties and crystallinity were investigated. Irradiation resulted in a significant decrease in molecular weight. At the same time, crystallinity of fiber mats increased significantly. However, the mechanical properties did not change significantly upon irradiation, mostly likely because effects of a lower molecular weight were balanced with the higher degree of crystallinity. The irradiation effects were dose dependent, a higher irradiation dose led to stronger changes. Gamma irradiation seemed to be the least suited method, while electron beams (ß irradiation) had a lower impact. Therefore, ß irradiation is recommended as sterilization method for electrospun PCL fiber mats.

Tailoring the mechanical and rheological properties of poly(lactic acid) by sterilizing UV-C irradiation.

In this study, we irradiated amorphous (A) and semi-crystalline (SC) poly(lactic acid) (PLA) with different UV-C doses up to 2214 kJ/m2. We achieved an average crystallinity of 43 % by heat treatment, which was unaffected by UV-C irradiation. Modulated differential scanning calorimetry showed that crystal polymorphs and the ratio of rigid amorphous and mobile amorphous phases were also unaffected. Using gel permeation chromatography analysis, we showed that the degradation mechanism was noncatalytic random scission, and the initial molar mass was reduced by >90 % at a dose of 2214 kJ/m2 for both A- and SC-PLA samples. Our Raman spectroscopy results indicated that the probability of the formation of oxygen-containing groups increases with increasing UV-C doses. Since we found that the mechanical properties of PLA films can be tailored with UV-C light, we proposed a method to predict the overall tensile curve as a function of the UV-C dose. We also proposed a modified Cross-WLF model to describe the effect of UV-C irradiation on viscosity up to 55 % molar mass reduction. The models allow us to estimate the limits of recyclability and reusability of sterilised PLA products.

Mechanistic insight into the photoconversion of losartan potassium mediated by different types of microplastics.

Nowadays the proliferation of microplastics (MPs) in aquatic environments and impacts on the fate of organic contaminants (OCs) has drawn sustained worldwide attention. In this study, we investigated the effects of different types and aging degrees of MPs, specifically polystyrene (PSMPs), polyethylene terephthalate (PETMPs), and polylactic acid (PLAMPs), on the photo-transformation of LSTPs. Our results revealed that the facilitation of LSTP photoconversion by PSMPs exhibited a positive linear relationship with aging degree. On the other hand, the effects of PETMPs with different oxidation levels on LSTP photoconversion were weak, while the contribution of PLAMPs decreased as aging increased. Characterizations, quenching and probing experiments showed the aging mechanisms and the generation of reactive oxygen species (ROS) converged among various MPs. Specifically, theoretical calculations, TOC and GC-MS were conducted to verify that in the PLA0-mediated systems, it was the intermediates of PLA0 that prevailed in promoting the photoconversion of LSTP. The aged PLA own have a large propensity to consume ROS, which diminished their promotion of LSTP degradation. This differd from the reactions involving PSMPs and PETMPs, where the microplastic particles themselves were the main drivers of the photoconversion process rather than intermediates.

Photodegradable polyesters for triggered release.

Photodegradable polyesters were synthesized with a photolabile monomer 2-nitrophenylethylene glycol and dioyl chlorides with different lengths. These polymers can be assembled to form polymeric particles with encapsulation of target substances. Light activation can degrade these particles and release payloads in both aqueous solutions and RAW 264.7 cells.

Cross-linked poly(trimethylene carbonate-co-L-lactide) as a biodegradable, elastomeric scaffold for vascular engineering applications.

A series of copolymers of trimethylene carbonate (TMC) and L-lactide (LLA) were synthesized and evaluated as scaffolds for the production of artificial blood vessels. The polymers were end-functionalized with acrylate, cast into films, and cross-linked using UV light. The mechanical, degradation, and biocompatibility properties were evaluated. High TMC polymers showed mechanical properties comparable to human arteries (Young's moduli of 1.2-1.8 MPa and high elasticity with repeated cycling at 10% strain). Over 84 days degradation in PBS, the modulus and material strength decreased gradually. The polymers were nontoxic and showed good cell adhesion and proliferation over 7 days using human mesenchymal stem cells. When implanted into the rat peritoneal cavity, the polymers elicited formation of tissue capsules composed of myofibroblasts, resembling immature vascular smooth muscle cells. Thus, these polymers showed properties which were tunable and favorable for vascular tissue engineering, specifically, the growth of artificial blood vessels in vivo.

Antibacterial functionalization of cotton and cotton/polyester fabrics applying hybrid coating of copper/chitosan nanocomposites loaded polymer blends via gamma irradiation.

In the present work, copper/chitosan nanocomposites (Cu/CS) were prepared in an aqueous solution in the presence of CS as stabilizer and CuSO4·5H2O precursor. The Cu/CS NPs formation was proved through transmission electron microscopy (TEM), Dynamic light scattering (DLS), Fourier Transform infrared (FT-IR) spectroscopy and XRD diffraction. Cotton and cotton/polyester fabrics were gamma-radiation grafted by padding to pickup of 100%, in nanocomposites based on Cu/CS NPs loaded in polymer blends of poly(vinyl alcohol) (PVA) and plasticized starch (PLST). The grafted fabrics were characterized in terms of tensile mechanical, crease recovery and water absorption properties. The results showed that cotton fabrics displayed higher water absorption (%) than cotton/polyester fabrics for all PVA/PLST compositions and water absorption was found to decrease with increasing the ratio of PVA in the PVA/PLST blends. Cotton/polyester fabrics displays crease recovery angle (CRA) value of 147.6 upon treated with PVA/PLST (80/20%) and gamma irradiated to 30 kGy compared to CRA value of 125.0 for cotton fabrics treated under the same conditions. For cotton fabrics, the tensile strength was largely depends on the irradiation dose, in which the tensile strength of the treated fabric with the different formulations is higher than the untreated fabric. The antimicrobial activity of the fabrics against gram-positive bacteria (Staphylococcus aurous) and gram-negative bacteria (Escherichia coli) was investigated. In case of gram-positive bacteria cotton fabric showed the highest impact, for both 50/50 and 20/80 PVA/PLST of 14 and 14.5 mm inhibition zone, whilst, cotton/polyester fabric recorded 6 and 5 mm inhibition zone against gram-negative bacteria for 50/50 and 20/80 PVA/PLST, respectively.

Photo-crosslinked anhydride-modified polyester and -ethers for pH-sensitive drug release.

Photo-crosslinkable polymers have a great potential for the delivery of sensitive drugs. They allow preparation of drug releasing devices by photo-crosslinking, thus avoiding high processing temperatures. In this study, the hydrolysis behavior and drug release of three different photo-crosslinkable poly(ether anhydride)s and one poly(ester anhydride) were investigated. Three-arm poly(ethylene glycol) or polycaprolactone was reacted with succinic anhydride to obtain carboxylated macromers, and further functionalized with methacrylic anhydride to form methacrylated marcromers with anhydride linkages. The synthetized macromers were used to prepare photo-crosslinked matrices with different hydrolytic degradation times for active agent release purposes. The hydrolysis was clearly pH-sensitive: polymer networks degraded slowly in acidic conditions, and degradation rate increased as the pH shifted towards basic conditions. Drug release was studied with two water-soluble model drugs lidocaine (234 mol/g) and vitamin B12 (1355 g/mol). Vitamin B12 was released mainly due to polymer network degradation, whereas smaller molecule lidocaine was released also through diffusion and swelling of polymer network. Only a small amount of vitamin B12 was released in acidic conditions (pH 1.3 and pH 2.1). These polymers have potential in colon targeted drug delivery as the polymer could protect sensitive drugs from acidic conditions in the stomach, and the drug would be released as the conditions change closer to neutral pH in the intestine.

In situ preparation of gold-polyester nanoparticles for biomedical imaging.

The synthesis and application of gold nanoparticles (AuNPs) have attracted much attention due to their interesting optical and chemical properties, as well as their utility in imaging, therapeutics, sensors, electronics, and catalysis. AuNPs are synthesized using multiple approaches, followed by chemical modification or encapsulation, to enhance their colloidal stability, biocompatibility, and targeting. Here, we report the one-step synthesis of gold-polyester nanoparticles for use as an imaging agent. The AuNPs were prepared inside polymeric NPs by means of ultraviolet irradiation of a gold salt in the presence of Irgacure I-2959 photoinitiator. We monitored the kinetic growth and nucleation of AuNPs (in vitro and ex vivo) over time using spectral analysis. Moreover, we investigated the cytotoxicity, localized plasmonic surface resonance (LSPR), and cellular imaging capabilities of the Au-polyester nanoparticles. The resulting Au-polyester NPs were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), dynamic light scattering (DLS), and transmission electron microscopy (TEM) to probe their chemical structure, size, zeta potential (ζ), and morphology, respectively. Furthermore, in vitro experiments showed that the NP formulation is stable over time and exhibits negligible toxicity against 3T3 fibroblast and U-87 MG glioblastoma cells. The results also demonstrated that the Au-polyester NPs exhibit excellent cellular imaging properties. This one-step strategy goes beyond current syntheses of gold-polyester nanoparticles because it can be used to synthesize the imaging agent in situ (i.e., in living cells) in lieu of conventional ex situ approaches.

Effect of sterilisation by gamma irradiation on the ability of polycaprolactone (PCL) to act as a scaffold material.

This paper investigates the effect of sterilisation by gamma irradiation (dose 2.5Mrad) on the following properties of polycaprolactone (PCL): (1) degradation rate (catalysed by lipase), (2) mechanical properties, (3) the ability of cells to attach and subsequently grow on its surface. Gel permeation chromatography (GPC) was used to determine the effects of gamma irradiation of weight average (M(w)) and number average (M(n)) molecular weights. Gamma irradiation significantly decreased the rate of degradation, although the rates depended on the initial mass of polymer; it also affected the appearance of the degraded specimens when they were examined by scanning electron microscopy. Irradiation also significantly increased the mechanical yield stress but not the failure stress of PCL. It caused a significant increase in M(w) and decrease in M(n) that could be attributed to chain scission and cross-linking. Chondrocyte attachment and growth on PCL was not significantly affected by gamma irradiation.

Matrix-assisted pulsed laser evaporation of poly(D,L-lactide) for biomedical applications: effect of near infrared radiation.

The deposition of thin films of poly(D,L-lactide) (PDLLA) by using the matrix-assisted pulsed laser evaporation (MAPLE) technique is investigated. PDLLA is a highly biocompatible and biodegradable polymer, with wide applicability in the biomedical field. The laser wavelength used in the MAPLE process is optimized to obtain a good-quality deposition. The structure of the polymer film is analyzed by Fourier transform infrared spectroscopy (FTIR). It is found that the chemical structure of PDLLA undergoes little or no damage during deposition with near-infrared laser radiation (1064 nm). It is thus confirmed that at this wavelength, the MAPLE technique can be applied for fragile biopolymer molecules, which are easily damaged by other laser radiations (UV radiation). This method allows future development of tailored polymer coatings for biomedical applications.

Photopolymerization and shrinkage kinetics of in situ crosslinkable N-vinyl-pyrrolidone/poly(epsilon-caprolactone fumarate) networks.

Biodegradable, injectable and in situ photocrosslinkable macromers based on fumaric acid and polycaprolactone (PCLF) were prepared and characterized by FTIR, 1HNMR, and 13CNMR spectroscopy. The multifunctional macromers dissolved in N-vinyl pyrollidone (NVP) were photopolymerized by visible light irradiation in the presence of camphorquinone as photoinitiator. The photocrosslinking reaction was monitored by measuring shrinkage strain and shrinkage strain rate. The degree of photopolymerization reaction i.e. degree of conversion (DC%) was traced using FTIR spectroscopy. A three level factorial design was developed to study the effects of initiator concentration, NVP concentration, and molecular weight of PCLF upon photocrosslinking characteristics including degree of conversion and shrinkage strain. Results revealed that although neat PCLF was photopolymerized, but it was putty like after 220 seconds of irradiation and showed a very low degree of conversion (29%). Adding about 20% NVP caused a dramatic increase in its degree of conversion (63.33%). Increasing NVP up to 50% resulted in a decrease in DC% because of lower reactivity of NVP and leaving more unreacted NVP monomers. Sol fraction studies supported these results indicating that at higher NVP concentration, most of NVP and PCLF have not undergone the crosslinking reaction, leading to 55% decrease in DC%. Shrinkage strain measurement also confirmed the FTIR results.

Development of a new photocrosslinkable biodegradable bioadhesive.

Adhesives provide a needle-free method of wound closure and do not require local anaesthetics. Polymeric adhesives have been used for about 3 decades for joining several tissues of the organism. Also, they can accomplish other tasks, such as haemostasis and the ability to seal air leakages and have the potential to serve as delivery systems. PCL was modified with 2-isocyanatoethylmethacrylate to form a macromer that was crosslinked via UV irradiation using Irgacure 2959 by CIBA as the photoinitiating agent. The characterization of the materials was accomplished by: attenuated total reflectance-Fourier transform infrared (ATR-FTIR), swelling capacity determination, evaluation of adhesive capacity (by reaction with aminated substrates) and determination of surface energy by contact angle measurement. Thermal characterization of the adhesive was performed by dynamical mechanical thermal analysis (DMTA) and thermogravimetric analysis (TGA). The morphology of PCL networks was observed using scanning electron microscopy (SEM) both after crosslinking process and following biodegradation in human plasma. The haemocompatibility of the membranes was also evaluated by thrombosis and haemolysis tests.

Effect of UV irradiation on the shear bond strength of titanium with segmented polyurethane through gamma-mercapto propyl trimethoxysilane.

The objective of this study was to investigate the effect of UV irradiation on shear bond strength between a titanium (Ti) and a segmented polyurethane (SPU) composite through gamma-mercapto propyl trimethoxysilane (gamma-MPS). To this end, the shear bond strength of Ti/SPU interface of Ti-SPU composite under varying conditions of ultraviolet ray (UV) irradiation was evaluated by a shear bond test. The glass transition temperatures of SPU with and without UV irradiation were also determined using differential scanning calorimetry. It was found that the shear bond strength of Ti/SPU interface increased with UV irradiation. However, excessive UV irradiation decreased the shear bond strength of Ti/SPU interface. Glass transition temperature was found to increase during 40-60 seconds of UV irradiation. In terms of durability after immersion in water at 37 degrees C for 30 days, shear bond strength was found to improve with UV irradiation. In conclusion, UV irradiation to a Ti-SPU composite was clearly one of the means to improve the shear bond strength of Ti/SPU interface.

Radiochromic film containing poly(hexa-2,4-diynylene adipate) as a radiation dosimeter.

A radiation-sensitive polymer poly(hexa-2,4-diynylene adipate) (PHDA) was synthesized and incorporated into polyvinyl butyral films for radiation dose measurements in the 0.5 - 60 kGy range. PHDA undergoes crosslinking polymerization upon exposure to γ-rays, which changes its color from very pale yellow to deep orange-yellow. The color change is directly related to the absorbed dose. The absorption spectrum of the irradiated films features one absorption band around 500 nm with a shoulder around 465 nm. With increasing absorbed dose, the two bands grow in intensity and move towards higher wavelengths. The dosimeter is nearly insensitive to variations of the humidity in the range of 0-54% and temperature in the range of 30-45 °C during irradiation. The color intensifies after irradiation, both in the dark and in the light at room temperature, which reflects the continuing crosslinking polymerization. However, at - 4 °C, the color intensity does not change with time.

Titania nanowires functionalized polyester fabrics with enhanced photocatalytic and antibacterial performances.

Flexible organic fabrics coated with titania find wide applications in pollutant degradations and antibiosis. Because of the enhanced charge separations, TiO2 with one-dimensional nanostructures exhibits photocatalytic activity superior to that of nanoparticulate films; however, only the later has been achieved on organic substrates through commonly sol-gel techniques till now. In this study, radially aligned TiO2 nanowires were precipitated on polyester fabrics through multi-steps of surface roughening, sol-gel TiO2 seeding, hydrogen titanate nanobelts precipitation, and finally sulfuric acid treatment. Both mesoporous anatase TiO2 nanowires and single-crystalline rutile TiO2 nanorods have been achieved, which, together with some unchanged titanate nanobelts, exhibited an overall narrowed band gap of ca. 2.50eV. The TiO2 nanowires on flexible PET fabrics showed higher photocatalytic activity towards degradations of not only rhodamine B in water but also toluene gas in air under UV light illumination, when compared with either TiO2 nanotube array or commercial Degussa P25 nanoparticulate films on metallic Ti substrates. Remarkable sterilization of E. coli and S. epidermidis under visible light irradiation was also achieved. The excellent photocatalytic and antibacterial performances were attributed to the unique mixed 1D nanostructures, phase junctions, abundant surface hydroxyl groups, and the narrowed band gap.

Rapid microwave assisted esterification method for the analysis of poly-3-hydroxybutyrate in Alcaligenes latus by gas chromatography.

In the present study, we used microwave energy instead of conventional heating to transform poly-3-hydroxybutyrate (PHB) into methyl 3-hydroxybutyrate (Me-3HB) in acidified methanol (H2SO4, 10%, v/v) mixture in less than 4 min at 10% microwave power. The microwave assisted method was then applied to analyze PHB produced by Alcaligenes latus. The PHB content in the biomass determined using microwave heating was comparable to the amount found by conventional heating. Moreover, the new esterification method was at least 50 times faster than the conventional method, affording a significant saving of time and energy.

Enhanced retention of polymer physical characteristics and mechanical strength of 70:30 poly(L-lactide-co-D,L-lactide) after ethylene oxide sterilization.

This study examined the effect of ethylene oxide (EtO) and electron beam (e-beam) irradiation on the properties of 70:30 poly(L-lactide-co-D,L-lactide). The effects of sterilization upon the polymer physical characteristics and strength retention of the material were examined, both initially and after being subjected to real time ageing. Commercially available 70:30 poly(L-lactide-co-D,L-lactide) material was fabricated into rectangular, cylindrical, screw, and sheet designs, and tested in compression, shear, or tension. Sterilization of 70:30 poly(L-lactide-co-D,L-lactide) by ethylene oxide had a nearly negligible effect on the physical properties of the polymer, regardless of specimen size or manufacturing technique. The molecular weight and inherent viscosity of the specimens decreased by approximately 3% after sterilization by EtO. However, sterilization of 70:30 poly(L-lactide-co-D,L-lactide) by e-beam irradiation resulted in immediate changes to some of the physical properties of the polymer. Specimens sterilized by e-beam irradiation displayed an immediate decrease in inherent viscosity of approximately 67% as compared to the respective nonsterile samples. The immediate decrease in inherent viscosity and molecular weight with e-beam irradiation required approximately 39 weeks of real time ageing of the EtO sterilized parts. At all time points investigated in the present study, the strength retention of the EtO sterilized devices equaled or exceeded that of the e-beam irradiated samples.

The beneficial influence of ultrasound in the polymerization of epsilon-caprolactam to polyamide-6 (Nylon 6). Part II: additional experiment to understand the "pre-sonication effect".

Ultrasound (US) "pre-sonication effect" is the beneficial effect of US in the hydrolytic polymerization of epsilon-caprolactam (CL) mixtures with very low water concentrations (about 0.1-1 wt%). It appears after a mild initial treatment of the mixtures with US [17.5-20 kHz, short times (5-15 min), low temperatures (70-110 degrees C)] followed by heating at 220-260 degrees C. An explanation is proposed on the basis of the formation in mild conditions (100 degrees C) of low concentrations of cyclic oligomers never detected in the literature at those conditions. These, under US irradiation, produce linear amino acid oligomers, which are strong activators of polymerization when the mixture of CL and water, after US irradiation, is heated at the suitable polymerization temperature indicated above.