Single-Particle Photothermal Circular Dichroism and Photothermal Magnetic Circular Dichroism Microscopy.

Recent advances in single-particle photothermal circular dichroism (PT CD) and photothermal magnetic circular dichroism (PT MCD) microscopy have shown strong promise for diverse applications in chirality and magnetism. Photothermal circular dichroism microscopy measures direct differential absorption of left- and right-circularly polarized light by a chiral nanoobject and thus can measure a pure circular dichroism signal, which is free from the contribution of circular birefringence and linear dichroism. Photothermal magnetic circular dichroism, which is based on the polar magneto-optical Kerr effect, can probe the magnetic properties of a single nanoparticle (of sizes down to 20 nm) optically. Single-particle measurements enable studies of the spatiotemporal heterogeneity of magnetism at the nanoscale. Both PT CD and PT MCD have already found applications in chiral plasmonics and magnetic nanomaterials. Most importantly, the advent of these microscopic techniques opens possibilities for many novel applications in biology and nanomaterial science.

Nanoscale Magneto-mechanical-genetics of Deep Brain Neurons Reversing Motor Deficits in Parkinsonian Mice.

Here, we introduce the magneto-mechanical-genetic (MMG)-driven wireless deep brain stimulation (DBS) using magnetic nanostructures for therapeutic benefits in the mouse model of Parkinson's disease (PD). Electrical DBS of the subthalamic nucleus (STN) is an effective therapy for mitigating Parkinson's motor symptoms. However, its broader application is hampered by the requirement for implanted electrodes and the lack of anatomical and cellular specificity. Using the nanoscale magnetic force actuators (m-Torquer), which deliver torque force under rotating magnetic fields to activate pre-encoded Piezo1 ion channels on target neurons, our system enables wireless and STN-specific DBS without implants, addressing key unmet challenges in the DBS field. In both late- and early-stage PD mice, MMG-DBS significantly improved locomotor activity and motor balance by 2-fold compared to untreated PD mice. Moreover, MMG-DBS enabled sustained therapeutic effects. This approach provides a non-invasive and implant-free DBS with cellular targeting capability for the effective treatment of Parkinsonian symptoms.

Innovative approach against cancer: Thymoquinone-loaded PHEMA-based magnetic nanoparticles and their effects on MCF-7 breast cancer.

Breast cancer is most common cancer among women in the World. Thymoquinone (TQ) exhibits a wide range of biological activities such as anticancer, antidiabetic, antimicrobial, analgesic, antioxidant, and anti-inflammatory effects. However, its effectiveness in cancer treatment is hindered by its poor bioavailability, attributed to its limited solubility in water. Hence, novel strategies are required to enhance the bioavailability of TQ, which possesses remarkable anticancer characteristics. The aim of this study is to prepare pHEMA-based magnetic nanoparticles carrying TQ (TQ-MNPs) to improve bioavailability, and therapeutic efficacy against breast cancer. For this purpose, TQ-MNPs were synthesized and characterized with Fourier transform infrared spectrophotometer (FTIR), scanning electron microscopy (SEM), dynamic light scattering (DLS), magnetic field using a vibrating sample magnetometer (VSM). The loading capabilities of synthesized magentic nanostructures were evaluated, and release investigations were conducted under experimental conditions that mimic the cellular environment. The findings of the studies indicated that the TQ carrying capacity of MNPs was deemed satisfactory, and the release efficiency was adequate. MNPs and TQ-MNPs showed biocompatibility against HDFa cells. TQ-MNPs showed stronger anti-proliferative activity against MCF-7 breast cancer cells compared to free TQ (p < 0.05). TQ-MNPs induced apoptosis in MCF-7 breast cancer cells.

Limits of Non-invasive Enzymatic Activation by Local Temperature Control.

Enzymatic activity depends on and can therefore be regulated by temperature. Selective modulation of the activity of different enzymes in one reaction pot would require temperature control local to each type of enzyme. It has been suggested previously that immobilization of enzyme on magnetic nanoparticles and exposing them to alternating magnetic field can enhance the reaction rate. This enhancement has been explained as being mediated by temperature increase caused by dissipation of the absorbed field energy in the form of heat. However, the possibility of spatially limiting this temperature increase on the microscale has been questioned. Here, it is investigated whether an activity enhancement of the enzyme sucrose phosphorylase immobilized on magnetic beads can be achieved, how this effect is related to the increase in temperature, and whether temperature differences within one reaction pot could be generated in this way. It is found that alternating magnetic field stimulation leads to increased enzymatic activity fully attributable to the increase of bulk temperature. Both theoretical analysis and experimental data indicate that no local heating near the particle surface takes place. It is further concluded that relevant increase of surface temperature can be obtained only with macroscopic, millimeter-sized, magnetic particles.

Magnetic nanoparticles fabricated/integrated with microfluidics for biological applications: A review.

Nanostructured materials have gained significant attention in recent years for their potential in biological applications, such as cell and biomolecular sorting, as well as early detection of metastatic cancer. Among these materials, magnetic nanoparticles (MNPs) stand out for their easy functionalization, high specific surface area, chemical stability, and superparamagnetic properties. However, conventional fabrication methods can lead to inconsistencies in MNPs' characteristics and performance, highlighting the need for a cost-effective, controllable, and reproducible synthesis approach. In this review, we will discuss the utilization of microfluidic technology as a cutting-edge strategy for the continuous and regulated synthesis of MNPs. This approach has proven effective in producing MNPs with a superior biomedical performance by offering precise control over particle size, shape, and surface properties. We will examine the latest research findings on developing and integrating MNPs synthesized through continuous microfluidic processes for a wide range of biological applications. By providing an overview of the current state of the field, this review aims to showcase the advantages of microfluidics in the fabrication and integration of MNPs, emphasizing their potential to revolutionize diagnostic and therapeutic methods within the realm of biotechnology.

Structure-Function Relationship of Iron Oxide Nanoflowers: Optimal Sizes for Magnetic Hyperthermia Depending on Alternating Magnetic Field Conditions.

Iron oxide nanoflowers (IONFs) that display singular magnetic properties can be synthesized through a polyol route first introduced almost 2 decades ago by Caruntu et al, presenting a multi-core morphology in which several grains (around 10 nm) are attached together and sintered. These outstanding properties are of great interest for magnetic field hyperthermia, which is considered as a promising therapy against cancer. Although of significantly smaller diameter, the specific adsorption rate (SAR) of IONFs reach values as large as for "magnetosomes" that are natural magnetic nanoparticles typically ~40 nm found in certain bacteria, which can be grown artificially but with much lower yield compared to chemical synthesis such as the polyol route. This work aims at better understanding the structure-property relationships, linking the internal IONF nanostructure as observed by HR-TEM to their magnetic properties. A library of mono- and multicore IONFs is presented, with diameters ranging from 11 to 30 nm in a narrow size distribution. More particularly, by relating their structural features to their magnetic properties investigated by utilizing AC magnetometry over a wide range of alternating magnetic field conditions, we showed that the SAR values of all synthesized batches vary with overall diameter and number of constituting cores.

Superparamagnetic Iron Oxide-Erastin-Polyethylene Glycol Nanotherapeutic Platform: A Ferroptosis-Based Approach for the Integrated Diagnosis and Treatment of Nasopharyngeal Cancer.

Erastin can induce ferroptosis in tumor cells as an effective small molecule inhibitor. However, its application is hampered by a lack of water solubility. This study investigated the effects of superparamagnetic iron oxide (SPIO)-erastin-polyethylene glycol (PEG) nanoparticles prepared by loading SPIO-PEG nanoparticles with erastin on ferroptosis. SPIO-erastin-PEG nanoparticles exhibited square and spherical shapes with good dispersibility. The zeta potential and hydrodynamic size of SPIO-erastin-PEG were measured as (-37.68 ± 2.706) mV and (45.75 ± 18.88) nm, respectively. On T2-weighted imaging, the nanosystem showed significant contrast enhancement compared to no-enhancement magnetic resonance imaging (MRI). SPIO-erastin-PEG induced ferroptosis by increasing reactive oxygen species and iron content and promoting the accumulation of lipid peroxides and the degradation of glutathione peroxidase 4. Pharmacokinetic experiments revealed a half-life of 1.25 ± 0.05 h for the SPIO-erastin-PEG solution in circulation. Moreover, significant antitumorigenic effects of SPIO-erastin-PEG have been demonstrated in 5-8F cells and mouse-bearing tumors. These results indicated that the synthesized SPIO-erastin-PEG nanoplatform could induce ferroptosis effects in vitro and in vivo while exhibiting favorable physical characteristics. This approach may provide a new strategy for theranostic nanoplatform for nasopharyngeal cancer.

Design of the distribution of iron oxide (Fe3O4) nano-particle drug in realistic cholangiocarcinoma model and the simulation of temperature increase during magnetic induction hyperthermia.

The prognosis for Cholangiocarcinoma (CCA) is unfavorable, necessitating the development of new therapeutic approach such as magnetic hyperthermia therapy (MHT) which is induced by magnetic nano-particle (MNPs) drug to bridge the treatment gap. Given the deep location of CCA within the abdominal cavity and proximity to vital organs, accurately predict the individualized treatment effects and safety brought by the distribution of MNPs in tumor will be crucial for the advancement of MHT in CCA. The Mimics software was used in this study to conduct three-dimensional reconstruction of abdominal computed tomography (CT) and magnetic reso-nance imaging images from clinical patients, resulting in the generation of a realistic digital geometric model representing the human biliary tract and its adjacent structures. Subsequently, The COMSOL Multiphysics software was utilized for modeling CCA and calculating the heat transfer law resulting from the multi-regional distribution of MNPs in CCA. The temperature within the central region of irregular CCA measured approximately 46°C, and most areas within the tumor displayed temperatures surpassing 41°C. The temperature of the inner edge of CCA is only 39 ∼ 41℃, however, it can be ameliorated by adjusting the local drug concentration through simulation system. For CCA with diverse morphologies and anatomical locations, the multi-regional distribution patterns of intratumoral MNPs and a slight overlap of drug distribution areas synergistically enhance intratumoral temperature while ensuring treatment safety. The present study highlights the practicality and imperative of incorporating personalized intratumoral MNPs distribution strategy into clinical practice for MHT, which can be achieved through the development of an integrated simulation system which incorporates medical image data and numerical calculations.

Anti-microbial, anti-biofilm, and efflux pump inhibitory effects of ellagic acid-bonded magnetic nanoparticles against Escherichia coli isolates.

The spread of microbial resistance is a threat to public health. In this study, the anti-microbial, anti-biofilm, and efflux pump inhibitory effects of ellagic acid-loaded magnetic nanoparticles (Fe3O4NPs@EA) against beta-lactamase producing Escherichia coli isolates have been investigated. The effects of Fe3O4 NPs@EA on the growth inhibition of E. coli isolates were determined by disc diffusion method and determining the minimum inhibitory concentration was done using broth micro-dilution method. The anti-biofilm effect of nanoparticles was investigated using the microplate method. The efflux pump inhibitory effect of nanoparticles was investigated using cart-wheel method and by investigating the effect of nanoparticles on acrB and tolC genes expression levels. Fe3O4 NPs@EA showed anti-bacterial effects against test bacteria, and the MIC of these nanoparticles varied from 0.19 to 1.56 mg/mL. These nanoparticles caused a 43-62% reduction in biofilm formation of test bacteria compared to control. Furthermore, efflux pump inhibitory effect of these nanoparticles was confirmed at a concentration of 1/8 MIC, and the expression of acrB and tolC genes decreased in bacteria treated with 1/4 MIC Fe3O4 NPs@EA. According to the results, the use of nanoparticles containing ellagic acid can provide a basis for the development of new treatments against drug-resistant E. coli. This substance may improve the concentration of antibiotics in the bacterial cell and increase their effectiveness by inhibiting the efflux in E. coli isolates.

Comparative evaluation of antimicrobial activity of spinel structured transition metal ferrites supported on reduced graphene oxide against pathogenic strains of bacteria and fungi.

One of the global challenges for living things is to provide pollution and harmful microbes-free environment. In this study, magnetically retrievable spinel-structured manganese zinc ferrite (Mn0.5Zn0.5Fe2O4) (MZF) was synthesized by a facile solvothermal method. Further, the MZF with different weight percentages (10 wt%, 50 wt%, and 80 wt%) were supported on reduced graphene oxide (rGO). The phase purity and morphology of MZF and MZF/rGO nanocomposite were confirmed by x-ray diffraction technique and scanning electron microscopy, respectively. The Fourier transform infrared spectroscopy, Raman, UV-visible spectroscopy, and thermogravimetric analyses of the as-synthesized nanocomposites were examined for the detection of various chemical groups, band gap, and thermal properties, respectively. The MZF/rGO nanocomposite exhibited significant antibacterial and antifungal activity againstEggerthella lenta, Enterococcus faecalis, Klebsiella pneumonia, Pseudomonas aeruginosa,andCandida albicanscompared to bare MZF and rGO. The high surface area of rGO plays a crucible role in antimicrobial analysis. Additionally, the antibacterial and antifungal activity is compared by synthesizing various metal ferrites such as MnFe2O4, ZnFe2O4, and Fe3O4. The 50 wt% MZF/rGO nanocomposite exhibits significantly high antibacterial activity. However, 10 wt% MZF/rGO nanocomposite shows good antifungal activity than Fe3O4, MnFe2O4, ZnFe2O4, MnZnFe2O4, 50 wt%, and 80 wt% MZF/rGO nanocomposites. These findings suggest that the prepared ferrite nanocomposites hold promise for microbial inhibition.

Low-temperature cluster spin glass transition in the single-domain NiCr2O4nanoparticles.

NiCr2O4nanoparticles with average particle size ∼15 nm, a single-domain size maintains the bulk canted antiferromagnetic ground state, were synthesized by a microwave combustion method. The magnetic behavior was carefully investigated by static and dynamic magnetic susceptibility measurements. In addition to a spin-glass-like behavior below paramagnetic-ferrimagnetic transition atTC, the NiCr2O4nanoparticles demonstrate a low-temperature cluster spin glass transition below the spin canting transitionTS, which manifests itself as a magnetic anomaly peak around ∼12 K (at 100 Oe) in the zero-field cooled magnetization with a relatively stronger field dependence in a 'de Almeida-Thouless' line for spin glasses. The AC susceptibility analyses in different approaches demonstrate a larger relative peak temperature variation per frequency decade and a longer characteristic relaxation time in the order of 0.04 and 10-7s, against 0.01 and 10-9s for the high-temperature blocking, indicating the slow spin dynamics for the low-temperature cluster glassy phase. A field-temperature magnetic phase diagram is proposed for the single-domain NiCr2O4nanoparticles.

Facile fabrication of Ti4+-immobilized magnetic nanoparticles by phase-transitioned lysozyme nanofilms for enrichment of phosphopeptides.

In this study, titanium (IV)-immobilized magnetic nanoparticles (Ti4+-PTL-MNPs) were firstly synthesized via a one-step aqueous self-assembly of lysozyme nanofilms for efficient phosphopeptide enrichment. Under physiological conditions, lysozymes readily self-organized into phase-transitioned lysozyme (PTL) nanofilms on Fe3O4@SiO2 and Fe3O4@C MNP surfaces with abundant functional groups, including -NH2, -COOH, -OH, and -SH, which can be used as multiple linkers to efficiently chelate Ti4+. The obtained Ti4+-PTL-MNPs possessed high sensitivity of 0.01 fmol µL-1 and remarkable selectivity even at a mass ratio of ß-casein to BSA as low as 1:400 for phosphopeptide enrichment. Furthermore, the synthesized Ti4+-PTL-MNPs can also selectively identify low-abundance phosphopeptides from extremely complicated human serum samples and their rapid separation, good reproducibility, and excellent recovery were also proven. This one-step self-assembly of PTL nanofilms facilitated the facile and efficient surface functionalization of various nanoparticles for proteomes/peptidomes.

Development of an innovative analytical method for forensic detection of cocaine, antidepressants, and metabolites in postmortem blood using magnetic nanoparticles.

Cocaine and antidepressants rank high globally in substance consumption, emphasizing their impact on public health. The determination of these compounds and related substances in biological samples is crucial for forensic toxicology. This study focused on developing an innovative analytical method for the determination of cocaine, antidepressants, and their related metabolites in postmortem blood samples, using unmodified commercial Fe3O4 nanoparticles as a sorbent for dispersive magnetic solid-phase extraction (m-d-SPE), coupled with liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) analysis. An aliquot of 100 µL of whole blood and 5 µL of the internal standard pool were added to 30 mg of nanoparticles. The nanoparticles were separated from the sample using a neodymium magnet inserted into a 3D-printed microtube rack. The liquid was then discarded, followed by desorption with 300 µL of 1/1/1 acetonitrile/methanol/ethyl acetate. The sample was vortexed and separated, and 1.5 µL of the organic supernatant was injected into the LC-MS/MS. The method was acceptably validated and successfully applied to 263 postmortem blood samples. All samples evaluated in this study were positive for at least one substance. The most frequent analyte was benzoylecgonine, followed by cocaine and cocaethylene. The most common antidepressants encountered in the analyzed samples were citalopram and fluoxetine, followed by fluoxetine's metabolite norfluoxetine. This study describes the first report of this sorbent in postmortem blood analysis, demonstrating satisfactory results for linearity, precision, accuracy, and selectivity for all compounds. The method's applicability was confirmed, establishing it as an efficient and sustainable alternative to traditional techniques for forensic casework.

Establishment of a multi-line immunochromatography based on magnetic nanoparticles for simultaneous screening of multiple biomarkers.

Biomarkers screening is a benefit approach for early diagnosis of major diseases. In this study, magnetic nanoparticles (MNPs) have been utilized as labels to establish a multi-line immunochromatography (MNP-MLIC) for simultaneous detection of carcinoembryonic antigen (CEA), carbohydrate antigen 199 (CA 19-9), and alpha-fetoprotein (AFP) in a single serum sample. Under the optimal parameters, the three biomarkers can be rapidly and simultaneously qualitative screening within 15 min by naked eye. As for quantitative detection, the MNP-MLIC test strips were precisely positioned and captured by a smartphone, and signals on the test and control lines were extracted by ImageJ software. The signal ratio of test and control lines has been calculated and used to plot quantitative standard curves with the logarithmic concentration, of which the correlation coefficients are more than 0.99, and the limit of detection for CEA, CA 19-9, and AFP were 0.60 ng/mL, 1.21 U/mL, and 0.93 ng/mL, respectively. The recoveries of blank serum were 75.0 ~ 112.5% with the relative standard deviation ranging from 2.5 to 15.3%, and the specificity investigation demonstrated that the MNP-MLIC is highly specific to the three biomarkers. In conclusion, the developed MNP-MLIC offers a rapid, simple, accurate, and highly specific method for simultaneously detecting multiple biomarkers in serum samples, which provides an efficient and accurate approach for the early diagnosis of diseases.

Chitosan decorated magnetic nanobiocatalyst of Bacillus derived α-amylase as a role model for starchy wastewater treatment, detergent additive and textile desizer.

In this study, Bacillus tequilensis TB5 α-amylase from rice-milled by-products (rice bran and de-oiled rice bran) was successfully immobilized onto biologically synthesized magnetic nanoparticles fabricated with chitosan (MNP-Ch) and characterized via different biophysical techniques. Furthermore, the study emphasized incorporating this nanostructure framework (MNP@2mgchitosan_DORB-amy and MNP@3mgchitosan_RB-amy) to offer diverse applications, including enzymatic desizing, cleaning starchy stains, and treating synthetic starchy wastewater. An enzyme loading of > 90 % for both enzymes indicated increased binding sites due to the functional moieties of chitosan on the MNP. The Km was 0.28 and 0.31 mg/mL for the immobilized and free forms of DORB-amy, respectively, and 0.18 and 0.27 mg/mL for the immobilized and free forms of RB-amy, respectively. A low Km indicated an increased affinity of MNP-Ch-immobilized forms of enzymes toward the substrate. The performance of both immobilized enzymes improved at a wide range of pH and temperature, which may be attributed to the covalent binding of the enzyme on to the MNP-Ch. The nanobiocatalysts in the detergent act synergistically to fade the starchy stains. Furthermore, an 8-9 TEGEWA scale rating with > 11 % of starch removal was obtained through the biodesizing of starch-sized cotton fabric. The nanobiocatalyst efficiently decomposed starch and liberated 650-670 mg/L of reducing sugar from the synthetic wastewater, therefore offering promising opportunities for its exploration in a wastewater treatment plant. Thus, the study recommends the potential exploration of sturdy matrices like MNP to offer remarkable applications with maximum operational stability, easier recovery, and higher efficiency.

Tri-layered core-shell structured deferoxamine magnetic particles promote Microcystis aeruginosa growth.

This experiment prepared magnetic composite siderophores (DMPs) with strong magnetism, excellent adsorption capacity, and high specific surface area. Exploring the synergistic effect of magnetic nanoparticles and siderophores on Microcystis aeruginosa growth under iron-deficient condition, by utilizing the characteristics of the three-layer core-shell structure of DMPs. This study elucidated the potential mechanism by which DMPs promote the cyanobacterial growth through physiological indicators and transcriptome analysis. On the experiment's final day, cell density in DMPs treatment group at 2, 4, and 8 mg/L were 1.10, 1.14 and 1.16 times higher than those in the control group (Ct), respectively. Similarly, chlorophyll and photosynthetic efficiency results showed improved algae growth with increasing DMPs dosage. The microcystin content in DMPs experimental groups at low, medium, and high concentration were 0.91, 0.86, and 0.83 times that of Ct, indicating alleviation of iron deficiency stress. Additionally, based on extracellular polymers, intracellular and extracellular siderophores, and visualization techniques, DMPs nanoparticles captured free iron sources in the environment, promoting algae growth by entering algal cells and facilitating the uptake and utilization of free iron ions from the solution. During the experiment, the iron uptake and transport genes (feoA and feoB) were significantly upregulated, whereas the algal siderophore synthesis gene (pchF) and the TonB-dependent transport system gene (TonB_C) were significantly downregulated, suggesting heightened activity in intracellular iron uptake and transport. This indicates an abundance of intracellular iron, eliminating the need for secrete siderophores to overcome iron deficiency. Microcystis aeruginosa increased iron bioavailability by using iron transported through DMPs in the environment while internalizing these DMPs. This study explored the mechanism of this synergistic effect to boost algal growth, and provided new ideas for elucidating the mechanism of cyanobacterial bloom outbreaks as well as the innovative application of biotechnology.

Magnetogenetics as a promising tool for controlling cellular signaling pathways.

Magnetogenetics emerges as a transformative approach for modulating cellular signaling pathways through the strategic application of magnetic fields and nanoparticles. This technique leverages the unique properties of magnetic nanoparticles (MNPs) to induce mechanical or thermal stimuli within cells, facilitating the activation of mechano- and thermosensitive proteins without the need for traditional ligand-receptor interactions. Unlike traditional modalities that often require invasive interventions and lack precision in targeting specific cellular functions, magnetogenetics offers a non-invasive alternative with the capacity for deep tissue penetration and the potential for targeting a broad spectrum of cellular processes. This review underscores magnetogenetics' broad applicability, from steering stem cell differentiation to manipulating neuronal activity and immune responses, highlighting its potential in regenerative medicine, neuroscience, and cancer therapy. Furthermore, the review explores the challenges and future directions of magnetogenetics, including the development of genetically programmed magnetic nanoparticles and the integration of magnetic field-sensitive cells for in vivo applications. Magnetogenetics stands at the forefront of cellular manipulation technologies, offering novel insights into cellular signaling and opening new avenues for therapeutic interventions.

The impact of heart valve and partial heart transplant models on the development of banking methods for tissues and organs: A concise review.

Cryopreserved human heart valves fill a crucial role in the treatment for congenital cardiac anomalies, since the use of alternative mechanical and xenogeneic tissue valves have historically been limited in babies. Heart valve models have been used since 1998 to better understand the impact of cryopreservation variables on the heart valve tissue components with the ultimate goals of improving cryopreserved tissue outcomes and potentially extrapolating results with tissues to organs. Cryopreservation traditionally relies on conventional freezing, employing cryoprotective agents, and slow cooling to sub-zero centigrade temperatures; but it is plagued by the formation of ice crystals and cell damage upon thawing. Researchers have identified ice-free vitrification procedures and developed a new rapid warming method termed nanowarming. Nanowarming is an emerging method that utilizes targeted application of energy at the nanoscale level to rapidly rewarm vitrified tissues, such as heart valves, uniformly for transplantation. Vitrification and nanowarming methods hold great promise for surgery, enabling the storage and transplantation of tissues for various applications, including tissue repair and replacement. These innovations have the potential to revolutionize complex tissue and organ transplantation, including partial heart transplantation. Banking these grafts addresses organ scarcity by extending preservation duration while preserving biological activity with maintenance of structural fidelity. While ice-free vitrification and nanowarming show remarkable potential, they are still in early development. Further interdisciplinary research must be dedicated to exploring the remaining challenges that include scalability, optimizing cryoprotectant solutions, and ensuring long-term viability upon rewarming in vitro and in vivo.

Development of a SERS aptasensor for the determination of L-theanine using a noble metal nanoparticle-magnetic nanospheres composite.

An ultrasensitive surface-enhanced Raman spectroscopy (SERS) aptamer sensor (aptasensor) using a noble metal nanoparticle-magnetic nanospheres composite was developed for L-theanine detection. It makes use of Fe3O4@Au MNPs and Au@Ag NPs embedded with the Raman reporter 4-mercaptobenzoic acid (4MBA). Au@4MBA@Ag NPs modified by aptamer and Fe3O4@Au MNPs modified by cDNA created the aptasensor with the strongest Raman signal of 4MBA through the specific binding of the aptamer. With the preferred binding of L-theanine aptamer to L-theanine, Au@4MBA@Ag NPs were released from Fe3O4@Au MNPs, causing a linear decrease in SERS intensity to achieve the SERS detection of the L-theanine. The SERS peak of 4MBA at 1078 cm-1 was used for quantitative determination. SERS intensity showed a good log-linear relationship within the range 10-10 to 10-6 M of L-theanine. The aptasensor has a high selectivity for L-theanine compared with other twelve tested analytes. Hence, this aptasensor is a promising analytical tool for L-theanine detection. The developed method was applied to the analysis of real samples, demonstrating excellent performance. The comparison with the standard liquid chromatography mass spectrometry method showed an error within 20%.

Mg2+- or Ca2+-regulated aptamer adsorption on polydopamine-coated magnetic nanoparticles for fluorescence detection of ochratoxin A.

It has been observed that polyvalent metal ions can mediate the adsorption of DNA on polydopamine (PDA) surfaces. Exploiting this, we used two divalent metal ions (Mg2+ or Ca2+) to promote the adsorption of fluorescence-labelled ochratoxin A (OTA) aptamers on PDA-coated magnetic nanoparticles (Fe3O4@PDA). Based on the different adsorption affinities of free aptamers and OTA-bound aptamers, a facile assay method was established for OTA detection. The aptamers adsorbed on Fe3O4@PDA were removed via simple magnetic separation, and the remaining aptamers in the supernatant exhibited a positive correlation with the OTA concentration. The concentrations of Mg2+ and Ca2+ were finely tuned to attain the optimal adsorption affinity and sensitivity for OTA detection. In addition, other factors, including the Fe3O4@PDA dosage, pH, mixing order, and incubation time, were studied. Finally, under optimized conditions, a detection limit (3σ/s) of 1.26 ng/mL was achieved for OTA. Real samples of spiked red wine were analysed with this aptamer-based method. This is the first report of regulating aptamer adsorption on the PDA surface with polyvalent metal ions for OTA detection. By changing the aptamers, the method can be easily extended to other target analytes.