Radiation synthesis and in vitro evaluation of the antimicrobial property of functionalized nanopolymer-based poly (propargyl alcohol) against multidrug-resistance microbes.

Pathogenic microorganisms are responsible for many diseases in biological organisms, including humans. Many of these infections thrive in hospitals, where people are treated with medicines and certain bacteria resist those treatments. Consequently, this research article aims to develop efficient antimicrobial material-based conjugated and functionalized polypropargyl alcohol nanoparticles (nano-PGA) synthesized by gamma irradiation. The monomer of PGA was polymerized in various mediums (water (W), chloroform (Ch), and dimethylformamide (DMF)) without catalysts under the action of γ-rays, producing π-conjugated and colored functional nano-PGA polymers. Nano-PGA is a versatile polymer demonstrated here as suitable for creating next-generation of antimicrobial systems capable of effectively preventing and killing various pathogenic microorganisms. The novelty here is the development of polymeric nanostructures by changing the solvent and irradiation doses. The antimicrobial property of nano-PGA (nanostare-like antibody structure) was examined against different pathogenic bacteria and unicellular fungi. Nano-PGA-DMF exhibits significant antimicrobial potential against Staphylococcus aureus (S. aureus) (20.20 mm; zone of inhibition (ZOI), and 0.47 µg/mL; minimum inhibitory concentration (MIC), followed by Escherichia coli (E. coli) (14.50 mm; ZOI, and 1.87 µg/mL; MIC, and Candida albicans (C.albicans) (12.50 mm; ZOI, and 1.87 µg/mL; MIC). In antibiofilm results, the highest inhibition percentage of the synthesized nano-PGA-W, nano-PGA-Ch, and nano-PGA-DMF was documented for S. aureus (17.01%, 37.57%, and 80.27%), followed by E. coli (25.68%, 55.16% and 78.11%), and C.albicans (40.10%, 62.65%, and 76.19%), respectively. The amount of bacterial protein removed is directly proportional after increasing the concentration of nano-PGA-W, nano-PGA-Ch, and nano-PGA-DMF samples (at different concentrations) and counted to be 70.58, 102.89, and 200.87 µg/mL, respectively following the treatment with 1.0 mg/mL of each sample. It was found that the nano-PGA polymer prepared in DMF has better antimicrobial activity than one prepared in chloroform than in water.

Study of Ag Nanoparticles in a Polyacrylamide Hydrogel Dosimeters by Optical Technique.

The dosimetric characteristics of hydrogel dosimeters based on polyacrylamide (PAC) as a capping agent incorporating silver nitrate as a radiation-sensitive material are investigated using UV-Vis spectrophotometry within the dose range 0-100 Gy. Glycerol was used in the hydrogel matrix to promote the dosimetric response and increase the radiation sensitivity. Upon exposing the PAC hydrogel to γ-ray, it exhibits a Surface Plasmon Resonance (SPR) band at 453 nm, and its intensity increases linearly with absorbed doses up to 100 Gy. The results are compared with the silver nitrate gel dosimeter. Glycerol of 15% in the hydrogel matrix enhances the radiation sensitivity by about 30%. PAC hydrogel dosimeter can be considered a near water equivalent material in the 400 keV-20 MeV photon energy range. At doses less than 15 Gy, the PAC hydrogel dosimeter retains higher radiation sensitivity than the gel dosimeter. The total uncertainty (2σ) of the dose estimated using this hydrogel is about 4%. These results may support the validity of using this hydrogel as a dosimeter to verify radiotherapy techniques and dose monitoring during blood irradiation.

A comparative dosimetry study of an alanine dosimeter with a PTW PinPoint chamber at ultra-high dose rates of synchrotron radiation.

The use of synchrotron X-ray sources provides innovative approaches in radiation therapy. The unique possibility to generate quasi-parallel beams promoted the development of microbeam radiation therapy (MRT), an innovative approach able to reduce damages to normal tissues while delivering considerable doses in the lesion. Accurate dosimetry in broad-beam configuration (prior to the spatial fractionation of the incident X-ray fan) is very challenging at ultra-high dose rate synchrotron sources. The available reference dosimetry protocol based on the use of a PTW PinPoint ionization chamber was compared with alanine dosimetry at the European Synchrotron Radiation Facility (ESRF) ID17 Biomedical beamline, an orthovoltage X-ray source with an average dose rate of 11.6 kGy/s. Reference dose measurements of the alanine pellets were performed at the National Centre for Radiation Research and Technology (NCRRT) 60Co facility in Egypt. All alanine dosimeters were analysed by an electron paramagnetic resonance spectrometer. We determined a relative response rESRF = 0.932 ± 0.027 (1σ) of the alanine pellets irradiated at the ESRF compared to the 60Co facility. Considering the appropriate corrections for the ESRF polychromatic spectrum and the different field size used, our result is in agreement with the previous work of Waldeland et al. for which the utilised alanine contained the same amount of binder, and it is consistent with the works of Anton et al. and Butler et al. for which the utilised alanine contained a higher amount of binder. We confirm that alanine is an appropriate dosimeter for ultra-high dose rate calibration of orthovoltage X-ray sources.

A new EPR dosimeter based on glutamic acid for radiation processing application.

L-Glutamic acid (L-GA) pellets (3.8 mm × 4 mm) and powder dosimeters were studied in the dose range of 0.1-150 kGy using the electron paramagnetic resonance (EPR) technique. The EPR spectra of irradiated L-GA pellets showed an EPR signal with eight lines, and the intensity of the signal increased with an increase of absorbed dose. The results obtained in terms of the energy-absorption coefficients suggest a similar performance of the L-GA pellets as compared to alanine pellets. The value of the temperature coefficient for the L-GA pellets during irradiation was around - 0.08%/°C which is lower than that reported for alanine dosimeter, 0.14%/°C. The influence of humidity on the pellet response was found to be negligible; i.e., the increase in response was only about 2% for a relative humidity of up to 94%. The response of L-GA powder reached stability 4 h after irradiation and continued to be stable until 47 days after irradiation. In contrast, the response of the L-GA pellet dosimeter reached stability 22 h after irradiation and continued to be stable until 8 days after irradiation. For routine applications, the L-GA pellet dosimeter should be analyzed during the stable period after irradiation, to minimize the uncertainties in dose assessment. The overall two-sigma uncertainties in absorbed dose estimation were 5.1% and 3.9% for the dose ranges of 0.1-15 kGy and 15-150 kGy, respectively. It is concluded that L-GA pellets represent a promising dosimeter material for quantification of radiation doses in food irradiation, medical sterilization and polymer modification.

Evaluations of N-(Isobutoxymethyl) acrylamide gel dosimeter by NMR technique for radiotherapy and uncertainty in dose measurements.

N-(Isobutoxymethyl) acrylamide (NIBMA) monomer in gelatin, named NIBMAGAT gel dosimeter, was prepared and investigated by nuclear magnetic imaging (NMR) for radiotherapy in the dose range of 0-30 Gy. NIBMA monomer polymerizes upon irradiation, increasing spin-spin relaxation rate R2. The addition of glycerol as a co-solvent in the gel matrix improved its radiation sensitivity better than the co-solvents of acetone and methanol. The increase of glycerol content by 1% wt/wt enhanced the sensitivity by ˜ 3.1%. This gel has better radiation sensitivity as compared to the polyacrylamide gel (PAG) dosimeter; the sensitivities of NIBMAGAT gel and normoxic polyacrylamide gel (nPAG) are ≈0.13 and ≈0.1 s-1.Gy-1, respectively. By comparing NIBMAGAT gel dosimeter with PAG, nMAG and nPAG gel dosimeters, NIBMAGAT gel dosimeter is less influenced by scanning temperature than the last three dosimeters. The gel is water equivalent and has an energy-independent response from 80 keV to 20 MeV. The overall uncertainty of dose measurement using NIBMAGAT gel is 5.46% at 2σ. Our findings suggest the applicability of using NIBMAGAT gel dosimeter by NMR technique for dose verification/planning in the practice of clinical radiotherapy.

Pergascript orange-based polymeric solution as a dosimeter for radiotherapy dosimetric validation.

A radiation colour former amino fluoran dye, Pergascript Orange (PGO), in a polyvinyl butyral solution containing a colour developer, hexachloroethane (HCE), was prepared and investigated for radiotherapy dosimetry of 60Co, 6 MV and 15 MV photons. PGO, a colourless dye, reacts with the acid produced upon radiation exposure of HCE, enabling the lactone ring to open and the orange colour of PGO to develop. The ring opening of PGO was confirmed by the appearance of a broad peak of OH- at 3360 cm-1, CO carboxylic peak at 1763 cm-1, and an iminium group peak at 1640 cm-1. The dose response of all prepared compositions was linear in the dose range of 1-20 Gy. Increasing HCE in the dosimeter matrix from 63 mM to 106 mM enhanced the radiation sensitivity by ≈58%. The radiation sensitivity of PGO-PVB (PGO-P) dosimeter is comparable with Fricke gel and higher than N-(Isobutoxymethyl) acrylamide polymer gel dosimeters. The experimental results reveal an energy-independent response (≈1.2% variation at 1σ) in the studied range of radiotherapy beam quality from 60Co beams to the beams from Linacs with a maximum energy of 15 MeV. Based on the theoretical study, this dosimeter is water equivalent from 80 keV to 10 MeV. The overall uncertainty was found to be 4.5% at the 95% confidence level, indicating the possibility of using PGO-P dosimeter in conventional radiotherapy dose verification.

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.

Fricke gel dosimeter as a tool in quality assurance of the radiotherapy treatment plans.

Ferrous xylenol gel was evaluated as a dosimeter in verifications of treatment plans for treatments of female breast tumors in external-beam radiation therapy. The dosimeter was calibrated in a cubic wax phantom irradiated with 6 and 15MV beams of an Elekta clinical linear accelerator and then used for measurements of doses in an anthropomorphic phantom of a female torso, which mimicked female breasts after modified radical mastectomy and breast-conserving surgery. Doses measured with the gel in specific locations in the phantom were compared with values predicted by treatment plans created with the XiO treatment planning system (Elekta / IMPAQ) and with results of measurements with an IBA CC13 ionization chamber in the same locations. Differences between the values measured with the gel and predicted by the treatment planning system or measured with the ionization chamber were within 1.5% in most cases. In an area of as steep dose gradient, the difference reached 2.7%, which was explicable in terms of the finite size of the gel dosimeter. The dose response of the gel is dose rate and energy independent in the ranges used in most clinical linacs. The results have shown that ferrous xylenol gels can be used as dosimeters in quality assurance in radiation therapy.