Radiation Crosslinking Research Articles

Development of gelatin nanoparticles for positron emission tomography diagnosis in pancreatic cancer

Abstract Pancreatic cancer remains difficult to diagnose using currently available imaging probes. Thus, this study aimed to develop a novel imaging agent for the diagnosis of pancreatic cancer using positron emission tomography (PET). Specifically, this study explores gelatin-based nanoparticles fabricated via radiation-induced crosslinking, as gelatin is known for its ability to produce biocompatible materials. Aqueous gelatin solutions were irradiated with γ-rays to produce nanoparticles with average diameters of 5–20 nm via a radiation crosslinking technique. The gelatin nanoparticles were labeled with 64Cu, exhibiting negative surface potentials. Furthermore, the nanoparticles were evaluated in vivo by injecting them into pancreatic tumor-bearing mice. Notably, the nanoparticles accumulated in the tumors. Hence, 64Cu-labeled gelatin nanoparticles show promise as a platform for next-generation PET imaging agents for pancreatic cancer.

Photo‐responsive systems based on anisotropic composites of poly(N‐vinyl formamide) and active fillers using directional freezing combined with gamma irradiation crosslinking

Photo‐responsive systems based on anisotropic composites of poly(<i>N</i>‐vinyl formamide) and active fillers using directional freezing combined with gamma irradiation crosslinking

Facile and rapid synthesis of core-shell structured MXene@Ag@PA hybrids for enhanced fire safety and radiation cross-linking in EVA/MH composites

In this study, MXene@Ag@PA hybrids were synthesized using radiation methods and chelation, aiming to enhance the key properties of EVA/MH composites, particularly their flame retardancy. The test results demonstrated that the addition of MXene@Ag@PA hybrids effectively reduced the amount of heat and smoke released during the combustion process of EVA composites. When 2 parts of MXene@Ag@PA hybrids were added, the peak heat release rate (pHRR) of the EVA/MH/2.0MXene@Ag@PA composite was reduced to 233 kW/m², representing a decrease of 78.5% and 63.3% compared to pure EVA and EVA/MH composites, respectively. Additionally, the time to reach the peak heat release rate was delayed to 300–400 s. Moreover, the MXene@Ag@PA hybrids further reduced the total smoke production (TSP) of the EVA composites to 3 m², which is 50% and 38.7% lower than that of pure EVA and EVA/MH composites, respectively. Besides providing significant flame-retardant enhancement to EVA/MH composites, the MXene@Ag@PA hybrids also acted as a radiation sensitizer. At an irradiation dose of 100 kGy, the addition of MXene@Ag@PA hybrids enhanced the cross-linking effect of EVA composites, thereby strengthening their mechanical properties.

Enhancing radiation resistance of silicone rubber through the addition of polydopamine-modified cerium dioxide

With the widespread use of nuclear science and technology, slowing down the aging of polymers in a radiation environment has become a matter of great concern. In this work, cerium dioxide (CeO2) and CeO2 encapsulated with dopamine (PDA@CeO2) were selected as special fillers to prepare the silicone rubber (SR) composites, and their radiation resistance were investigated by comparing the mechanical properties and thermal performance before and after irradiation. The interfacial bridge formed by PDA results in a greater elongation at break for PDA@CeO2/SR5.0 (770.0 ± 33.6 %) than for CeO2/SR (686.0 ± 15.0 %). After irradiation with γ-rays, the retention of elongation at break of both CeO2/SR0.1 and PDA@CeO2/SR0.1 were larger than SR. Furthermore, PDA@CeO2/SR0.1 showed an impressive retention of 90.5 ± 2.7 % of the tensile strength retention after exposure to an absorbed dose of 200 kGy. The disparity in crosslink density prior to and following irradiation indicated that both CeO2 and PDA@CeO2 were efficacious in reducing radiation crosslinking within the SR. An electron paramagnetic resonance spectrometer and an ultraviolet lamp (UV-EPR) were used to observe in real time the free radical scavenging ability of CeO2 and PDA@CeO2 inside the SR. These results indicated that CeO2 and PDA@CeO2 was expected to prevent further chain reactions in silicone rubber by scavenging free radicals generated in SR, thus improving the radiation resistance of SR.

Simultaneously enhanced antioxidation and wear resistance in UHMWPE molded plastic by adding natural polyphenol antioxidant

Ultrahigh-molecular-weight polyethylene (UHMWPE), with its excellent wear resistance and biocompatibility, has important application as artificial joints. The most commonly used method to improve its wear resistance is to introduce crosslinking through irradiation. However, free radicals are introduced after radiation, which are easy to cause inflammation in the human body. Some antioxidants, such as vitamin E (VE), need to be added. However, the addition of VE could reduce the crosslinking density of UHMWPE and worsen the wear resistance of the material. Therefore, obtaining new antioxidants that could eliminate free radicals without affecting or even improving the crosslinking density of materials during irradiation is an important subject worth exploring. In this paper, a kind of natural polyphenol substance, resveratrol (RSV), was introduced as a new antioxidant and crosslinking promoter during irradiation crosslinking of UHMWPE. RSV can better eliminate free radicals than VE and further improve the crosslinking density to obtain UHMWPE materials with excellent oxidation resistance and high wear resistance. The multi-active phenolic hydroxyl structure of RSV molecule provides its free-radical trapping ability, and the appropriate molecular size of RSV may promote the H-type crosslinking of UHMWPE, thereby increasing the crosslinking density. This work provides a new pathway for developing high-performance artificial joint prosthesis materials.

Polypropylene Films for HVDC Capacitors With Enhanced Dielectric Performance by Irradiation Crosslinking Modification

Polypropylene Films for HVDC Capacitors With Enhanced Dielectric Performance by Irradiation Crosslinking Modification

Low-Density and High-Performance Fiber-Reinforced PP/POE Composite Foam via Irradiation Crosslinking.

This study addresses the challenge of achieving foam with a high expansion ratio and poor mechanical properties, caused by the low melt viscosity of semi-crystalline polypropylene (PP). We systematically employ a modification approach involving blending PP with polyolefin elastomers (POE), irradiation crosslinking, and fiber reinforcement to prepare fiber-reinforced crosslinked PP/POE composite foam. Through optimization and characterization of material composition and processing conditions, the obtained fiber-reinforced crosslinked PP/POE composite foam exhibits both low density and high performance. Specifically, at a crosslinking degree of 12%, the expansion ratio reaches 16 times its original value, and a foam density of 0.057 g/cm3 is reduced by 36% compared to the non-crosslinked PP/POE system with a density of 0.089 g/cm3. The density of the short-carbon-fiber-reinforced crosslinked sCF/PP/POE composite foam is comparable to that of the crosslinked PP/POE system, but the tensile strength reaches 0.69 MPa, representing a 200% increase over the crosslinked PP/POE system and a 41% increase over the non-crosslinked PP/POE system. Simultaneously, it exhibits excellent impact strength, tear resistance, and low heat shrinkage. Irradiation crosslinking is beneficial for enhancing the melt strength and resistance to high temperature thermal shrinkage of PP/POE foam, while fiber reinforcement contributes significantly to improving mechanical properties. These achieve a good complementary effect in low-density and high-performance PP foam modification.

Diffusion doping of analgesics into UHMWPE for prophylactic pain management.

Pain management after total joint arthroplasty is often addressed by systemic delivery of opioids. Local delivery of non-opioid analgesic drugs directly in the joint space from the UHMWPE component of the prosthesis would be highly beneficial to increase the efficacy of the drugs, decreasing the overall side effects and the risk of opioid addiction. It has been shown that effective concentrations of local analgesics can be achieved by eluting from analgesic-blended UHMWPE; however, this approach is limited by the decrease in mechanical properties resulting from the extent of phase separation of the blended drugs from the polymeric matrix. Here we hypothesized that mechanical properties could be maintained by incorporating analgesics into solid form UHMWPE by diffusion as an alternative method. Lidocaine or bupivacaine were diffused in solid form UHMWPE with or without radiation crosslinking. The loaded drug content, the spatial distribution of the drugs and their chemical stability after doping were characterized by FTIR and NMR spectroscopy, respectively. Drug release kinetics, tensile mechanical properties and wear rates were assessed. The results showed that diffusion doping could be used as a promising method to obtain a therapeutic implant material without compromising its mechanical and structural integrity.

Dielectric performance improvement of polypropylene film modified by γ-ray irradiation for HVDC capacitors

Polypropylene (PP) films exhibit low dielectric strength and high losses under elevated temperatures and strong electric field environments. This paper proposes a method to improve the dielectric properties based on γ-ray irradiation crosslinking, investigates the effect of the type of sensitizer on the crosslinking reaction, and explores the effect of crosslinking structure on the dielectric properties of PP films such as breakdown strength. The results showed that the type of group in the sensitizer influenced its activity in the crosslinking reaction, and the modified films added with pentaerythritol triacrylate (PETA) exhibited the highest crosslinking degree of 25.68%. In addition, it was found that the crosslinked structure improved the stability of the molecular chains at high temperatures and reduced the probability of thermal breakdown. At 115 °C, the modified films with PETA showed a 72.5% reduction in conductivity and a 33.6% increase in breakdown strength. This method demonstrates the importance of irradiation crosslinking modification for improving the reliability of PP films in high-temperature and strong electric field applications.

“To Be or Not to Be” of a Polymer Nanogel—Unravelling the Relationship of Product Properties vs. Synthesis Conditions Governing the Radiation Crosslinking of Poly(acrylic acid) Using GPC/SEC—MALLS

In this paper, a state-of-the-art multi-detection gel permeation chromatography/size exclusion chromatography (GPC/SEC) system including multi-angle laser light scattering (MALLS) is applied to monitor radiation-induced synthesis of internally crosslinked nanostructures from poly(acrylic acid) (PAA). The aim is to demonstrate that this modern tool yields a more detailed picture of reaction mechanism and product structure than the techniques used to date. The prevailing intramolecular crosslinking narrows the molecular weight distribution from Mw/Mn = 3.0 to 1.6 for internally crosslinked structures. A clear trend from over 0.7 to 0.5 in the Mark–Houwink exponent and a decrease in Rg/Rh from 1.7 to 1.0 point to the formation of nanogels, more rigid and less permeable than the starting coils. Changes in the coil contraction factor (g′ = [η]irradiated/[η]linear) as a function of the radical density revealed the existence of two modes in intramolecular crosslinking, the initial one (up to 0.075 radicals per monomer unit) where the compactness of products changes strongly with progressing crosslinking and a second one where further compacting is suppressed by the lower flexibility of the partially crosslinked chain segments. This indicates a transition from soft, still internally crosslinkable nanogels to more rigid structures, less prone to further intramolecular loop formation. Our findings provide means for the tailored design of new PAA nanomaterials.

Radiation crosslinking and grafting of chitosan: Conversion of biowaste to an efficient adsorbent for removal of cationic dyes

By the mutual radiation grafting technique using Co60 gamma radiation, a novel anionic adsorbent “CRChitosan-g-SSS” was developed where in p-Sodium Styrene Sulphonate was covalently grafted onto crosslinked chitosan backbone. The synthesized radiation-grafted adsorbent was tested for the adsorptive removal of cationic dyes: methylene blue, malachite green and Congo red from aqueous solutions. The adsorbed amount of the respective dyes was 89.12, 73.13, and 29.14 (mg/g) respectively, which could be better described with Langmuir isotherm and pseudo-second-order reaction according to the correlation coefficient values, indicating favorable and feasible adsorption. Various factors influencing the adsorption capacity of“CRChitosan-g-SSS” like initial dye concentration, contact time, solution pH, and temperature were also studied. Different thermodynamic parameters such as standard free energy, standard enthalpy, and standard entropy were calculated which revealed the adsorption process to be exothermic and spontaneous. The radiation-grafted anionic adsorbent showed promising properties for the removal of toxic cationic dyes (i.e. Methylene blue, Malachite green, and Congo red).

Radiation-Induced Alteration of the Reflection Spectra of Diazoquinone–Novolac Photoresist Films by Implantation of Ag+ Ions

FP9120 diazoquinone–novolac positive photoresist films 1.5 μm thick implanted with Ag+ ions and supported on the surface of KDB-10 (111) silicon wafers by centrifugation have been studied by measuring reflection spectra. It has been shown that ion implantation leads to a decrease in the refractive index of the photoresist due to radiation crosslinking of novolac resin molecules and a decrease in the density ρ and the molecular refraction RM of the photoresist. It has been established that the reflection coefficient in the opaque region of the photoresistive film increases with the Ag+ implantation dose. The changes observed in the optical properties of the films under ion implantation conditions are explained taking into account radiation-chemical processes in the phenol–formaldehyde photoresist.

Radiation cross-linking of pH-sensitive acrylic acid hydrogel based polyvinylpyrrolidone/ 2-dimethylamino ethyl methacrylate loaded with betamethasone dipropionate drug and in vitro anti-inflammatory assessment

Radiation cross-linking of pH-sensitive acrylic acid hydrogel based polyvinylpyrrolidone/ 2-dimethylamino ethyl methacrylate loaded with betamethasone dipropionate drug and in vitro anti-inflammatory assessment

Additive Free Crosslinking of Poly-3-hydroxybutyrate via Electron Beam Irradiation at Elevated Temperatures.

When applying electron or gamma irradiation to poly-3-hydroxybutyrate (P3HB), main chain scissions are the dominant material reactions. Though propositions have been made that crosslinking in the amorphous phase of P3HB occurs under irradiation, a conclusive method to achieve controlled additive free irradiation crosslinking has not been shown and no mechanism has been derived to the best of our knowledge. By applying irradiation in a molten state at 195 °C and doses above 200 kGy, we were able to initiate crosslink reactions and achieved gel formation of up to 16%. The gel dose Dgel was determined to be 200 kGy and a range of the G values, the number of scissions and crosslinks for 100 eV energy deposition, is given. Rheology measurements, as well as size exclusion chromatography (SEC), showed indications for branching at doses from 100 to 250 kGy. Thermal analysis showed the development of a bimodal peak with a decrease in the peak melt temperature and an increase in peak width. In combination with an increase in the thermal degradation temperature for a dose of 200 kGy compared to 100 kGy, thermal analysis also showed phenomena attributed to branching and crosslinking.

The effect of modified carbon-doped boron nitride on the mechanical, thermal and γ-radiation stability of silicone rubber composites

The developing nuclear technology has increased the need for radiation-resistant and shielding materials. It is crucial to study the radiation resistance of polymers in order to prevent safety incidents brought on by the degradation of polymer performance in a nuclear environment. In this work, γ-aminopropyltriethoxy silane (KH550) was successfully grafted onto carbon-doped boron (BCN) to obtain modified BCN (BCN-KH550), then BCN-KH550 was added in silicone rubber and refined and vulcanized. The elongation at break of silicone rubber composite doped with 0.3 phr BCN-KH550 can retain (54 ± 2)% of the initial value. The addition of BCN and BCN-KH550 both increases the initial decomposition temperature of the irradiated SR. The radiation caused changes in crystallinity and glass transition temperature (Tg) were measured using differential scanning calorimetry. The difference Tg of BCN-KH550/SR0.3 before and after irradiation is 0.9 °C higher than that of SR. It is supposed that BCN protects the side group of SR during irradiation through differential thermogravimetric analysis curve and gas phase infrared spectra of the irradiation-induced gas products. BCN and BCN-KH550 can lower the hydrocarbon, CO2 and CO production by side chain breakdown in both air and nitrogen atmospheres. The presence of BCN and BCN-KH550 decrease the radiation crosslinking of SR. The outcomes demonstrate that BCN-KH550 can reduce the effects of γ-radiation crosslinking on SR by declining side chain decomposition.

Hydrogelation of Regenerated Silk Fibroin via Gamma Irradiation.

Gamma irradiation, which is one of the more conventional sterilization methods, was used to induce the hydrogelation of silk fibroin in this study. The physical and chemical characteristics of the irradiation-induced silk fibroin hydrogels were investigated. Silk fibroin solution with a concentration greater than 1 wt% formed hydrogel when irradiated by gamma rays at a dose of 25 or 50 kGy. The hydrogel induced by 50 kGy of radiation was more thermally stable at 80 °C than those induced by 25 kGy of radiation. When compared to the spontaneously formed hydrogels, the irradiated hydrogels contained a greater fraction of random coils and a lower fraction of β-sheets. This finding implies that gelation via gamma irradiation occurs via other processes, in addition to crystalline β-sheet formation, which is a well-established mechanism. Our observation suggests that crosslinking and chain scission via gamma irradiation could occur in parallel with the β-sheet formation. The irradiation-induced hydrogels were obtained when the solution concentration was adequate to support the radiation crosslinking of the silk fibroin chains. This work has, therefore, demonstrated that gamma irradiation can be employed as an alternative method to produce chemical-free, random coil-rich, and sterilized silk fibroin hydrogels for biomedical applications.

Development of environmentally friendly soft contact lenses made from cellulose-derived hydrogel materials

With the performance improvement of soft contact lenses (SCLs) over the past few decades, their global use and market have steadily expanded. Consequently, contamination by disposable SCLs has become a potential threat to the environment. From the perspective of sustainable development goals, overcoming this issue requires the development of new biodegradable SCL materials based on plant-derived cellulose. In this study, highly transparent hydrogels based on hydroxypropyl cellulose were prepared via a radiation crosslinking technique using electron beams. By optimizing the irradiation dose and type of added monomer, excellent physicochemical properties, such as mechanical strength and transparency, and biological properties, such as low lysozyme deposition and biodegradability, were obtained. Thus, hydrogels produced by radiation crosslinking can be potentially used as human- and environment-friendly SCL materials.

Di-cumyl peroxide cross-linked UHMWPE/vitamin-E blend for total joint arthroplasty implants.

Majority of ultrahigh molecular weight polyethylene (UHMWPE) medical devices used in total joint arthroplasty are cross-linked using gamma radiation to improve wear resistance. Alternative methods of cross-linking are urgently needed to replace gamma radiation due to rapid decline in its supply. Peroxide cross-linking is a candidate method with widespread industrial applications. Oxidative stability and biocompatibility, which are critical requirements for medical device applications, can be achieved using vitamin-E as an additive and by removing peroxide by-products through high-temperature melting, respectively. We investigated compression molded UHMWPE/vitamin-E/di-cumyl peroxide blends followed by high-temperature melting in inert gas as a material candidate for tibial knee inserts. Wear resistance increased and mechanical properties remained largely unchanged. Oxidation induction time was higher than most of the other clinically available formulations. The material passed the local-end point biocompatibility tests per ISO 10993. Compounds found in exhaustive extraction were of no concern with margin-of-safety values well above the accepted level, indicating a desirable toxicological risk profile. Statement of Clinical Significance: Peroxide cross-linked, vitamin-E stabilized, and high-temperature melted UHMWPE has recently been cleared for clinical use in tibial knee inserts. With all the salient characteristics needed in a material that can provide superior long-term performance in total joint patients, peroxide cross-linking can replace the gamma radiation cross-linking of UHMWPE.

Enhancing water flux and rejection performance through UV crosslinking: Optimization of surface modification of polyacrylonitrile (PAN)/acrylonitrile butadiene rubber (NBR) blend membrane using benzophenone as a crosslinking agent

Polyacrylonitrile (PAN)/acrylonitrile butadiene rubber (NBR) blend membranes were prepared by the phase inversion method using dimethylformamide as solvent. The blend membrane with a ratio of 85:15 was modified by ultraviolet (UV) radiation crosslinking of NBR using benzophenone as the crosslinking agent. The blend membrane was characterized through Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), porosity, contact angel, tensile strength, pure water flux, and rejection measurements. The blend membrane showed an increased pure water flux and decreased BSA rejection. However, the addition of benzophenone and UV radiation reduced the porosity and flux of the membrane, while improving the tensile strength and BSA rejection. The response surface method (RSM) with central composite design (CCD) using Design Expert software was employed to optimize the modification conditions of the PAN/NBR blend membrane, and the suggested membrane contained 2.5 wt% benzophenone and was exposed to UV radiation for 2 h. This membrane showed a pure water flux of 95.3 L/m2h, BSA rejection of 81.1%, and a tensile strength of 4.01 MPa, which is a 45% increase in water flux compared to the neat PAN membrane while showing better rejection and preserving the desired mechanical properties.

Influence of gamma irradiation on acrylate‐based shape memory polymers in the presence of various crosslinkers

AbstractThis study investigates the impact of gamma irradiation on acrylate‐based shape memory polymers (SMPs) when combined with various crosslinkers. The SMPs were synthesized using butyl acrylate (nBuA) and isobornyl acrylate (IBoA) with different crosslinkers, including polyethylene glycol diacrylate (PEGDA), bisphenol A ethoxylated diacrylate (BPAEDA), and trimethylolpropane triacrylate (TMPTA). The photo‐initiation process utilized 2,2 dimethoxy‐2‐phenylacetophenone (DMPA), followed by gamma radiation crosslinking at absorbed doses ranging from 5 to 300 kGy. The degree of gelation depended on the copolymer composition and irradiation dose, with poly(IBoA‐nBuA)‐BPAEDA exhibiting the highest gelation degree (99%) and poly(IBoA‐nBuA)‐TMPTA showing the lowest (86%). Fourier transform infrared spectroscopy analysis confirmed the copolymer structure, while thermal stability was assessed using thermogravimetric analysis and differential scanning calorimetry. Dynamic mechanical analysis analysis of the copolymers revealed significant variations in mechanical properties based on the type of crosslinker, radiation dose, and copolymer composition. Furthermore, the shape memory behavior of the copolymers was examined, demonstrating temperature‐dependent storage and loss moduli for crosslinked poly(IBoA‐nBuA) copolymers at a radiation dose of 150 kGy. In summary, the findings highlight that gamma irradiation crosslinking and the choice of crosslinkers have a substantial impact on the properties of acrylate‐based SMPs.