Construction of a sensitive and selective plasmonic biosensor for prostate specific antigen by combining magnetic molecularly-imprinted polymer and surface-enhanced Raman spectroscopy.

Selective and sensitive detection of cancer biomarkers in serum samples is critical for early diagnosis of cancer. Prostate specific antigen is an important biomarker of prostate cancer, which ranks high among cancer-related deaths of men over 50 years old. Herein, a novel analytical method was introduced for detection of PSA by combining high selectivity of molecularly-imprinted polymers and high sensitivity of surface-enhanced Raman spectroscopy (SERS). Firstly, magnetic nanoparticles were grafted with an imprinted layer by using tannic acid as a functional monomer, diethylenetriamine as a cross-linker and prostate specific antigen as a template molecule. Detailed surface characterization and re-binding experiment results indicated that the imprinting of the antigen was successful with an imprinting factor of 5.58. The prepared magnetic molecularly imprinted polymers (MMIPs) were used as an antibody-free capture probe and labeled with gold nanoparticles that were modified with anti-PSA and a Raman reporter, namely 5,5'-dithiobis-(2-nitrobenzoic acid). Thus, a plasmonic structure (sandwich complex) was formed between MMIP and the SERS label. The limit of detection and limit of quantification of the designed sensor were 0.9 pg/mL and 3.2 pg/mL, respectively. The sensor also showed high recovery rates (98.0-100.1% for healthy person and 99.0-101.3% for patient) with low standard deviations (less than 4.3% for healthy person and less than 3.3% for patient) for PSA in serum samples. Compared with the traditional immunoassays, the proposed method has several advantages like low cost, reduced detection procedure, fast response, high sensitivity and selectivity. It is believed that the proposed method can be potentially used for selective and sensitive determination of tumor marker of prostate cancer in clinical applications.

Health risk assessment of chromium contamination in the nearby population of mining plants, situated at Balochistan, Pakistan.

The main objective of this work was to investigate the root cause(s) of the various diseases in the local population, living in the proximity of chromium mining area. The analytical work was done on the samples of drinking water, soil and human blood, collected from the study area. The chosen study area is known as Muslim Bagh, located in the Balochistan province of Pakistan. The area is well-known for chromite hub. The hub comprises about 325 open-cast and underground mines, 100 dumping sites and 11 chrome beneficiation plants. The presented investigation is the first report of its nature on the contamination of heavy metals (HM) in the samples of drinking water and soil of the study area. The traces of different HM were also found in the random blood samples of human population in the study area. The amount of Co, Ni, Pb, As and Cr in the soil samples of the study area was obtained in the range of 990 × 103-1837 × 103, 1 × 103-11 × 103, 1 × 103-15 × 103, 84 × 103-187 × 103 and 6.9 × 106-19.5 × 106 (µg/kg ppb), respectively, whereas the samples of drinking water of the area found were 199-997 Co, 40-1370 Ni, 30-740 Pb, 47-890 As and 1990-13,530 (µg/kg ppb) of Cr. The obtained data of the physiochemical properties and the amount of HM show that the available drinking water sources are unfit for human consumption, mainly because of the chromium amount. Questionnaire analysis of the local population was also revealed that there was no awareness or feeling about metal poisoning in the targeted people and had no idea about the metal contaminations and diseases caused by this. Human health risk assessment for both carcinogenic and non-carcinogens concludes that the children and adults of the area are at high risk of several diseases and disorders.

A fluorescent artificial receptor with specific imprinted cavities to selectively detect colistin.

A novel and facile fluorescent artificial receptor on the basis of the molecularly imprinted polymer-coated graphene quantum dots was engineered successfully to detect colistin. The colistin imprinted graphene quantum dots (CMIP-GQDs) was synthesized by vinyl-based radical polymerization between functional monomers and crosslinker at around the template molecule on the surface of graphene quantum dots. The size of bare, CNIP-GQDs, and CMIP-GQDs was about 4.8 ± 0.6 nm, 18.4 ± 1.7 nm, and 19.7 ± 1.3 nm, respectively. The CMIP-GQDs, which showed the strong fluorescence emission at 440 nm with the excitation wavelength fixed at 380 nm, had excellent selectivity and specificity to rapidly recognize and detect colistin. The linear range of fluorescence quenching of this fluorescent artificial receptor for detection colistin was 0.016-2.0 µg mL-1 with a correlation coefficient (R2) of 0.99919, and the detection limit was 7.3 ng mL-1 in human serum samples. The designed receptor was successfully applied to detect colistin in human serum samples and it achieved excellent recoveries shifted from 93.8 to 105%. Graphical abstract.

Magnetic nanoparticles coated with different shells for biorecognition: high specific binding capacity.

Modifying the surfaces of magnetic nanoparticles (MNPs) by the covalent attachment of biomolecules will enable their application as media for magnetically-assisted bioseparations. In this paper, we reported both the activity and specific binding capacity of ferritin antibodies on core-shell MNPs. The antibodies were covalently attached on silica-, silver- and polydopamine-coated MNPs by different methods. Anti-ferritin was bound onto the silica- or silver-coated MNPs by conventional methods using 3-aminopropyltriethoxysilane (APTES) or 11-mercaptoundecanoic acid (MUA), which was followed by activation of carboxyl groups by EDC/NHS. However with anti-ferritin immobilized onto the Fe3O4 nanoparticles modified with polydopamine, an in situ coating formed through the adhesive proteins. In addition, a great deal of anti-ferritin biomolecules covalently attached onto the MNPs. According to our results, the amounts of bound anti-ferritin onto the silica-, silver- and PDA-coated MNPs were 70, 75 and 95 µg anti-ferritin per mg MNP, respectively. In the experiments, polydopamine (PDA)-coated MNPs showed faster adsorption, more significant selectivity and a larger binding capacity than the others. Also, the equilibrium dissociation constants of the antigen-antibody complexes were determined on the anti-ferritin-immobilized MNPs. Silica-, PDA- and silver-coated MNPs had Kd values of 5.45 × 10(-7), 2.12 × 10(-7) and 3.91 × 10(-8) mol L(-1), respectively. Based on these results, the affinity of the anti-ferritin for ferritin on the PDA-coated MNPs was approximately 10-fold higher than that on the silica- and silver-coated MNPs. In addition, among the anti-ferritin-immobilized silica-, silver- and PDA-coated MNPs, the PDA-coated MNPs showed the highest antigen selectivity values. As a result, anti-ferritin-immobilized PDA-coated MNPs represented a higher activity and stronger affinity for the specific antigen than the others.

Core-shell magnetic nanoparticles: a comparative study based on silica and polydopamine coating for magnetic bio-separation platforms.

Core-shell magnetic nanoparticles (MNPs) offer tremendous opportunities in a large range of applications in biomedicine due to their superior magnetic properties, biocompatibility and suitability for modification. In most cases, these characteristic features are determined by their shell chemistry and morphology. Herein, we demonstrate a comparative study of silica and polydopamine (PDOP) coating onto MNP surfaces based on synthesis, characterization and usage in a bio-separation platform. It was found that monodispersed MNPs may be easily obtained on silica coating of varying shell thickness, whereas a continuous PDOP layer observed around the MNPs prevents the formation of the dispersed form. On the other hand, PDOP coated MNPs exhibited better superparamagnetic behavior and biological modification ability compared to the silica coated form.

Dependence of protein recognition of temperature-sensitive imprinted hydrogels on preparation temperature.

Temperature-sensitive imprinted and non-imprinted hydrogels composed of N-isopropylacrylamide (NIPA) and 2-acrylamido-2-methyl-propanosulfonic acid (AMPS) have been prepared by free-radical crosslinking copolymerization in aqueous solution at three different temperatures: 10 degrees C (below the lower critical solution temperature, LCST), 33 degrees C (at the LCST), and 40 degrees C (above the LCST). Myoglobin (Mb, MW 17 kDa) is used as the template biomolecule. The effects of the initial concentration and adsorption time over the Mb adsorption capacity of the hydrogels have been analyzed and found to be strongly dependent on the preparation temperature (T(prep)). The maximum Mb adsorption for the imprinted hydrogel prepared at 10 degrees C is 97.40 +/- 2.35 mg Mb x g(-1) dry gel in 0.32 mg x mL(-1) Mb solution at 22 degrees C. Moreover, batch adsorption equilibrium and selectivity studies have been performed using a reference molecule, hemoglobin (Hb, MW 65 kDa). The imprinted hydrogels have a 2.8-3.3 times higher adsorption capacity for Mb than the non-imprinted hydrogels prepared at the same T(prep)s, and also have a 1.8-2.7 times higher selectivity for the imprinted molecule.

Hemoglobin recognition of molecularly imprinted hydrogels prepared at different pHs.

The hemoglobin-imprinted hydrogels were fabricated by using N-t-butylacrylamide (TBA) acrylamide (AAm) and itaconic acid (IA) monomers and hemoglobin (Hb, MW 65 kDa) imprinted molecule in pH buffer solutions (pH 4.0, 6.8 and 8.0). The nonimprinted hydrogels were also prepared at same conditions without Hb imprinting molecule. The effects of pH, initial concentration and adsorption time over the Hb adsorption capacity of both imprinted and nonimprinted hydrogels were analyzed and found to be strongly dependent on the preparation pH (pH(prep)). The maximum Hb adsorption for the imprinted hydrogel prepared at pH 4.0 was found to be 12.4 mg protein g(-1) dry gel in pH 4.0 buffer solution. This behavior was attributed to the formation of more accessible adsorption sites (imprints) because of the non-covalent interactions between the template and network during formation in pH 4.0 buffer solution which is below of the isoelectric point (pI 6.8) of Hb. Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherm. Langmuir analysis showed that an equal class of adsorption was formed in the hydrogels. Moreover, batch adsorption equilibrium and selectivity studies were also performed by using two reference molecules as fibrinogen (Fb, MW 340 kDa) and myoglobin (Mb, MW 17 kDa). The imprinted hydrogels have 1.5-2.2 times higher adsorption capacity for Hb than the nonimprinted hydrogels prepared at the same pHs, and also have 2.0-3.1 times higher selectivity for the imprinted molecule.

pH/temperature - sensitive imprinted ionic poly(N-tert-butylacrylamide-co-acrylamide/maleic acid) hydrogels for bovine serum albumin.

In this study, we have prepared pH/temperature-sensitive imprinted ionic poly(N-tert-butylacrylamide-co-acrylamide/maleic acid) [P(TBA-co-AAm/MA)] hydrogels for bovine serum albumin (BSA) by using molecular imprinting method. BSA adsorption from aqueous BSA solutions was investigated with two types of hydrogel systems prepared by non-imprinted and imprinted methods. Hydrogels imprinted with BSA showed higher adsorption capacity and specificity for BSA than hydrogels prepared by the usual procedure. At all studied conditions, the highest BSA adsorption was observed in the hydrogel imprinted with 8.63 wt.-% BSA. In addition, the imprinted hydrogels exhibited both for good selectivity BSA and high adsorption rate depending on the number of BSA-sized cavities. Adsorption studies showed that other stimuli, such as pH, temperature and initial BSA concentration also influenced the BSA adsorption capacity of both non-imprinted and imprinted hydrogels.