Vacuum ultraviolet treatment of polyethylene to change surface properties and characteristics of protein adsorption

Influence of ultraviolet and chemical treatment on the biodegradation of low-density polyethylene and high-density polyethylene by Cephalosporium strain

In the present work, the potential of Cephalosporium strain in degrading the pre-treated (ultraviolet irradiation followed by nitric acid treatment) low-density polyethylene and high-density polyethylene films was investigated. Our observations revealed a significant weight reduction of 24.53 ± 0.73% and 18.22 ± 0.31% in pre-treated low-density polyethylene and high-density polyethylene films respectively, after 56 days of incubation with the Cephalosporium strain. Changes in the physicochemical properties of the mineral salt medium (MSM) were studied to assess the extent of biodegradation. The pH of the MSM decreased gradually during the incubation period, whereas its total dissolved solids and conductivity values increased steadily. Fourier transform infrared spectroscopy (FTIR) indicated the formation of hydroxyl and C = C groups in biodegraded low-density polyethylene films, while in the case of biodegraded high-density polyethylene films it indicated the [Formula: see text]CH₂ stretching. Furthermore, the thermogravimetric analysis (TGA) revealed an enhancement in the thermal stabilities of both the LDPE and HDPE films post the biodegradation. Modifications in the polymer surface morphologies after UV irradiation, chemical treatment, and biodegradation steps were visualized via scanning electron microscopy (SEM) analysis. All our observations confirm the ability of the Cephalosporium strain in biodegrading the pre-treated LDPE and HDPE films.

Vacuum ultraviolet nonlinear metalens

Vacuum ultraviolet (VUV) light plays an essential role across science and technology, from molecular spectroscopy to nanolithography and biomedical procedures. Realizing nanoscale devices for VUV light generation and control is critical for next-generation VUV sources and systems, but the scarcity of low-loss VUV materials creates a substantial challenge. We demonstrate a metalens that both generates-by second-harmonic generation-and simultaneously focuses the generated VUV light. The metalens consists of 150-nm-thick zinc oxide (ZnO) nanoresonators that convert 394 nm (~3.15 eV) light into focused 197-nm (~6.29 eV) radiation, producing a spot 1.7 μm in diameter with a 21-fold power density enhancement as compared to the wavefront at the metalens surface. The reported metalens is ultracompact and phase-matching free, allowing substantial streamlining of VUV system design and facilitating more advanced applications. This work provides a useful platform for developing low-loss VUV components and increasing the accessibility of the VUV regime.

Role of pretreatment and evidence for the enhanced biodegradation and mineralization of low-density polyethylene films by greater waxworm

The present study reports the role of pretreatment for the enhanced biodegradation of low-density polyethylene (LDPE) with Galleria mellonella (Greater waxworm). The pretreatment of the LDPE film was carried out under solar radiation. The pretreated LDPE (PTLDPE) and untreated LDPE (UTLDPE) were characterized with AFM, FTIR and ¹H NMR techniques. The qualitative analysis for the biodegradation of pretreated and untreated LDPE was examined by analysing the Excreta residue (ER) of Galleria mellonella fed with LDPE. The mineralization of the ER of waxworm fed on Waxcomb (WC), UTLDPE and PTLDPE were studied by analysing the changes in physiochemical properties through FTIR, ¹H NMR and GC-MS techniques in addition to weight loss percentage of PTLDPE and survival rates of the tested greater waxworms. Solar pretreatment of LDPE led to increased surface roughness which favoured the waxworms to feed voraciously on PTLDPE. The post degradation studies of Waxcomb (WC), PTLDPE and UTLDPE showed 92.03 ± 2.1%, 18.57 ± 1.8% and 55.8 ± 1.2% weight loss, respectively. The FTIR, ¹H NMR and GC-MS results confirm that the ER of waxworm fed on WC, UTLDPE and PTLDPE showed the presence of new carbonyl and alcoholic groups with increase in unsaturated hydrocarbon indicating enhanced mineralization of LDPE. The efficient mineralization of PTLDPE by waxworm was observed without affecting its survivability. A plausible mechanism of LDPE degradation has also been proposed. The rapid and cost effective biodegradation of PTLDPE through waxworm paves a new and facile route for hazardous plastic waste treatment.

Mesoporous silica/protein biocomposites: Surface, topography, thermal properties

The biocomposite systems based on mesoporous MCF silica support and protein molecules are characterized with regard to their surface, topographic, thermal properties. Mesoporous silica materials (MCF) covered by the adsorbed protein molecules (BSA and OVA) were examined and characterized by using various techniques including X-ray diffraction, the Fourier transform infrared spectroscopy with attenuated total reflectance, X-ray photoelectron spectroscopy and scanning electron microscopy with microanalysis. The results of study focused on a detailed analysis of microstructure (topography, texture), and chemistry (chemical bonds, functional groups, elemental composition) of protein/mesoporous silica biocomposite. Moreover, the thermal properties of prepared biomaterials were investigated by means of TG/DSC-FTIR-MS-coupled technique. These powerful methods provided detailed information for understanding protein adsorption on MCF. Significant differentiation in surface chemistry and topography of MCF material was observed after protein adsorption. Basing on the results of thermal analysis stronger changes of the surface properties and more stable interactions of biomolecules with MCF-d16 support were observed for larger BSA molecules compared to smaller ovalbumin ones.

Spectroscopic investigation of water-soluble alloyed QDs with bovine serum albumin

We present here a systematic investigation on the interaction between a water-soluble alloyed semiconductor quantum dot and bovine serum albumin using various spectroscopic techniques i.e. fluorescence quenching, resonance light scattering and synchronous fluorescence spectroscopy. The analysis of fluorescence spectrum and fluorescence intensity indicates that the intrinsic fluorescence of bovine serum albumin (BSA) gets quenched by both static and dynamic quenching mechanism. The Stern-Volmer quenching constants, energy transfer efficiency parameters, binding parameters and corresponding thermodynamic parameters (ΔH⁰ , ΔS⁰ and ΔG⁰ ) have been evaluated by using van 't Hoff equation at different temperatures. A positive entropy change with a positive enthalpy change was observed suggesting that the binding process was an entropy-driven, endothermic process associated with the hydrophobic effect. The intermolecular distance (r) between donor (BSA) and acceptor (CdSeS/ZnS quantum dots) was estimated according to Förster's theory of non-radiative energy transfer. The synchronous fluorescence spectra revealed a blue shift in the emission maxima of tryptophan which is indicative of increasing hydrophobicity. Negative ΔG⁰ values implied that the binding process was spontaneous. It was found that hydrophobic forces played a role in the quenching process. Copyright © 2016 John Wiley & Sons, Ltd.

Adsorption of albumin and sodium hyaluronate on UHMWPE: a QCM-D and AFM study

The biotribological properties of artificial joints, in particular the efficiency of the lubrication, strongly determine their lifetime. The most commonly used artificial joints combine a metallic or ceramic part articulating against a ultra high molecular weight polyethylene (UHMWPE) counterface, and are lubricated by the periprosthetic fluid. This fluid contains several macromolecules, namely albumin and sodium hyaluronate (NaHA), that are known to be involved in the lubrication process. There are several studies in the literature concerning the interaction of the referred macromolecules with ceramic or metallic prosthetic materials. However, to our knowledge, information about their binding to the polymeric surface is practically inexistent. The objective of this work is to contribute to clarify the role played by albumin and NaHA on the biolubrication process, through the investigation of their interaction with the UHMWPE surface. The study involves adsorption measurements using a quartz crystal microbalance with dissipation (QCM-D), the characterization of the adsorbed films by atomic force microscopy (AFM) and wettability determinations. Albumin was found to adsorb strongly and extensively to the polymer, while NaHA led to a very low adsorption. In both cases rigid films were obtained, but with different morphology and porosity. The high binding affinity of the protein to the polymer was demonstrated both by the results of the fittings to Langmuir and Freundlich models and by the values of the adhesion forces determined by AFM. In the simultaneous adsorption of albumin and NaHA, protein adsorption is predominant and determines the surface properties.

Attachment of horseradish peroxidase to polytetrafluorethylene (teflon) after plasma immersion ion implantation

The aim of this work was to investigate the potential of polytetrafluorethylene (PTFE) as a surface for biologically active protein attachment. A plasma immersion ion implantation (PIII) treatment was applied to PTFE to produce an activated surface for the functional attachment of the enzyme, horseradish peroxidase (HRP). Fourier transform infrared-attenuated total reflectance spectra show oxidation and carbonization of the surface layer as a function of ion fluence. The PIII treatment increases by threefold the amount of attached HRP and the activity of HRP on the modified surface is about seven times higher than that on an untreated PTFE surface. This result indicates that the PIII surface modification improves both the polymer's protein binding capacity and its ability to retain the protein in a bioactive state.

Calcium phosphate formation on plasma immersion ion implanted low density polyethylene and polytetrafluorethylene surfaces

The flexible structure of polymers has enabled them to be useful in a wide variety of medical applications due to the possibility to tailor their properties to suit desired applications. For a long time, there has been an increasing interest in utilizing polymers as matrices for calcium phosphate-based composites with applications in hard tissue implants. On the other side, polymers with application as heart valves, urea catheters and artificial vessels present a case where the formation of minerals (namely calcification) should be avoided. The modification of polymer surfaces by various ion beam treatments for reducing the calcification, as for example plasma immersion ion implantation (PIII), is well known and has a long time effect. This work is part of a wider investigation of the ability of plasma immersion ion implanted polymers to induce calcium phosphate formation from an aqueous solution resembling the human blood plasma. In the experiment described in this paper, topographical and chemical changes were inserted on the surfaces of two conventional polymers (low density polyethylene and polytetrafluorethylene) by PIII with nitrogen ions, and under conditions mimicking the natural mineral formation processes. The effect of the plasma modification on the calcium phosphate nucleation and growth from the aqueous solution was ambiguous. We suppose that the complex combination of surface characteristics influenced the ability of the plasma treated polymer films to induce the formation of a calcium phosphate layer.