Gold nanoparticles-doped MXene heterostructure for ultrasensitive electrochemical detection of fumonisin B1 and ampicillin.

Early transition metal carbides (MXene) hybridized by precious metals open a door for innovative electrochemical biosensing device design. Herein, we present a facile one-pot synthesis of gold nanoparticles (AuNPs)-doped two-dimensional (2D) titanium carbide MXene nanoflakes (Ti3C2Tx/Au). Ti3C2Tx MXene exhibits high electrical conductivity and yields synergistic signal amplification in conjunction with AuNPs leading to excellent electrochemical performance. Thus Ti3C2Tx/Au hybrid nanostructure can be used as an electrode platform for the electrochemical analysis of various targets. We used screen-printed electrodes modified with the Ti3C2Tx/Au electrode and functionalized with different biorecognition elements to detect and quantify an antibiotic, ampicillin (AMP), and a mycotoxin, fumonisin B1 (FB1). The ultralow limits of detection of 2.284 pM and 1.617 pg.mL-1, which we achieved respectively for AMP and FB1 are far lower than their corresponding maximum residue limits of 2.8 nM in milk and 2 to 4 mg kg-1 in corn products for human consumption set by the United States Food and Drug Administration. Additionally, the linear range of detection and quantification of AMP and FB1 were, respectively, 10 pM to 500 nM and 10 pg mL-1 to 1 µg mL-1. The unique structure and excellent electrochemical performance of Ti3C2Tx/Au nanocomposite suggest that it is highly suitable for anchoring biorecognition entities such as antibodies and oligonucleotides for monitoring various deleterious contaminants in agri-food products.

LSPR-based colorimetric biosensing for food quality and safety.

Ensuring consistently high quality and safety is paramount to food producers and consumers alike. Wet chemistry and microbiological methods provide accurate results, but those methods are not conducive to rapid, onsite testing needs. Hence, many efforts have focused on rapid testing for food quality and safety, including the development of various biosensors. Herein, we focus on a group of biosensors, which provide visually recognizable colorimetric signals within minutes and can be used onsite. Although there are different ways to achieve visual color-change signals, we restrict our focus on sensors that exploit the localized surface plasmon resonance (LSPR) phenomenon of metal nanoparticles, primarily gold and silver nanoparticles. The typical approach in the design of LSPR biosensors is to conjugate biorecognition ligands on the surface of metal nanoparticles and allow the ligands to specifically recognize and bind the target analyte. This ligand-target binding reaction leads to a change in color of the test sample and a concomitant shift in the ultraviolet-visual absorption peak. Various designs applying this and other signal generation schemes are reviewed with an emphasis on those applied for evaluating factors that compromise the quality and safety of food and agricultural products. The LSPR-based colorimetric biosensing platform is a promising technology for enhancing food quality and safety. Aided by the advances in nanotechnology, this sensing technique lends itself easily for further development on field-deployable platforms such as smartphones for onsite and end-user applications.

Integrating Electrochemical Immunosensing and Cell Adhesion Technologies for Cancer Cell Detection and Enumeration.

We have successfully integrated techniques for controlling cell adhesion and performing electrochemical differential pulse voltammetry (DPV) through the use of digitally controlled microfluidics and patterned transparent indium tin oxide electrode arrays to enable rapid and sensitive enumeration of cancer cells in a scalable microscale format. This integrated approach leverages a dual-working electrode (WE) surface to improve the specificity of the detection system. Here, one of the WE surfaces is functionalized with anti-Melanocortin 1 Receptor antibodies specific to melanoma cancer cells, while the other WE acts as a control (i.e., without antibody), for detecting non-specific interactions between cells and the electrode. The method is described and shown to provide effective detection of melanoma cells at concentrations ranging between 25 to 300 cells per 20 µL sample volume after a 5 min incubation and 15 s of DPV measurements. The estimated limit of detection was ~17 cells. The sensitivity and specificity of the assay were quantified using addition of large fractions of non-target cells and resulted in a detection reproducibility of ~97%. The proposed approach demonstrates a unique integration of electrochemical sensing and microfluidic cell adhesion technologies with multiple advantages such as label-free detection, short detection times, and low sample volumes. Next steps for this platform include testing with patient samples and use of other cell-surface biomarkers for detection and enumeration of circulating tumor cells in prostate, breast, and colon cancer.

Use of cationic polymers to reduce pathogen levels during dairy manure separation.

Various separation technologies are used to deal with the enormous amounts of animal waste that large livestock operations generate. When the recycled waste stream is land applied, it is essential to lower the pathogen load to safeguard the health of livestock and humans. We investigated whether cationic polymers, used as a flocculent in the solid/liquid separation process, could reduce the pathogen indicator load in the animal waste stream. The effects of low charge density cationic polyacrylamide (CPAM) and high charge density cationic polydicyandiamide (PDCD) were investigated. Results demonstrated that CPAM was more effective than PDCD for manure coagulation and flocculation, while PDCD was more effective than CPAM in reducing the pathogen indicator loads. However, their combined use, CPAM followed by PDCD, resulted in both improved solids separation and pathogen indicator reduction.

Determining the gelation temperature of ß-lactoglobulin using in situ microscopic imaging.

Evolution of microstructure during heat-induced gelation of ß-lactoglobulin (ß-LG) was investigated in situ using confocal laser scanning microscopy at various gel-preparation conditions: pH=2, 5, and 7; protein content=5, 10, and 15%; and salt (NaCl) content=0, 0.1, and 0.3 M. The number and area of evolving ß-LG clusters were observed as a function of time and temperature and the data were fitted to a log-normal model and sigmoid model, respectively. The gelation temperature (Tgel) of the ß-LG system was determined from both the number (Tgel/N) and total area (Tgel/A) of ß-LG clusters versus temperature data. The range of Tgel/N and Tgel/A values for all the cases was 68 to 87°C. The effect of pH was the most dominant on Tgel/N and Tgel/A, whereas the effects of ß-LG and salt contents were also statistically significant. Therefore, the combined effect of protein concentration, pH, and salt content is critical to determine the overall gel microstructure and Tgel. The Tgel/N and Tgel/A generally agreed well with Tgel determined by dynamic rheometry (Tgel/R). The correlations between Tgel/N and Tgel/A versus Tgel/R were 0.85 and 0.72, respectively. In addition, Tgel/N and Tgel/A values compared well with Tgel/R values reported in the literature. Based on these results, Tgel/N determined via in situ microscopy appears to be a fairly good representative of the traditionally measured gelation temperature, Tgel/R.

Nanozymatic degradation and simultaneous colorimetric detection of tetracycline.

Tetracycline (TC) is a broad-spectrum antibiotic that can enter and accumulate in the human body via the food chain. Even in small concentrations, TC can cause several malignant health effects. We developed a system to simultaneously degrade the presence of TC in food matrices using titanium carbide MXene (FL-Ti3C2Tx). The FL-Ti3C2Tx exhibited biocatalytic property that activates hydrogen peroxide (H2O2) molecules in 3, 3', 5, 5'-tetramethylbenzidine (TMB environment. During the FL-Ti3C2Tx reaction, the catalytic products released turn the color of the H2O2/TMB system bluish-green. However, when TC is present, the bluish-green color does not appear. Via quadrupole time-of-flight mass spectrometry, we found that the TC is degraded by FL-Ti3C2Tx / H2O2 in preference to H2O2/TMB redox reaction, which intervenes in the color change. Hence, we developed a colorimetric assay to detect TC with a LOD of 615.38 nM and proposed two TC degradation pathways that facilitate the highly sensitive colorimetric bioassay.

MXene-Based Nucleic Acid Biosensors for Agricultural and Food Systems.

MXene is a two-dimensional (2D) nanomaterial that exhibits several superior properties suitable for fabricating biosensors. Likewise, the nucleic acid (NA) in oligomerization forms possesses highly specific biorecognition ability and other features amenable to biosensing. Hence the combined use of MXene and NA is becoming increasingly common in biosensor design and development. In this review, MXene- and NA-based biosensors are discussed in terms of their sensing mechanisms and fabrication details. MXenes are introduced from their definition and synthesis process to their characterization followed by their use in NA-mediated biosensor fabrication. The emphasis is placed on the detection of various targets relevant to agricultural and food systems, including microbial pathogens, chemical toxicants, heavy metals, organic pollutants, etc. Finally, current challenges and future perspectives are presented with an eye toward the development of advanced biosensors with improved detection performance.

Emulsion gels loaded with pancreatic lipase: Preparation from spontaneously made emulsions and assessment of the rheological, microscopic and cargo release properties.

Emulsion gels are solidified emulsions, which can be used for delivery of both hydrophilic and lipophilic substances. In this research, at first fish oil-in-water (O/W; 10% w/w) emulsions were prepared through the spontaneous emulsification technique. As emulsifier, a blend of the small-molecule surfactant tween 80, and either low-acyl (LaG) or high-acyl (HaG) gellan was used. For making fully stable (100% stability index) emulsions, a 10-fold higher concentration of LaG than HaG in the emulsion aqueous phase was required. The difference in gellan concentration resulted in a bigger mean drop size, as well as lesser consistency coefficient and yield stress for HaG emulsion than LaG emulsion. Subsequently, the fully stable HaG and LaG emulsions were gelled by CaCl2 addition. LaG emulsion gel was self-supporting and had a dense microstructure (as observed by electron microscopy), whereas HaG emulsion gel was not self-supporting. Loading lipase into the emulsions before ionotropic gelation did not lead to unacceptable acid values for fish oil during the emulsion gels storage. When the lipase-loaded fish O/W emulsion gels were immersed in an acid solution which imitated the gastric fluid (yet without digestive enzymes) oil droplets flocculated (as observed by confocal microscopy). The acid immersion also increased the dynamic moduli of the gels. Lipase was not released into the surrounding acid solution from LaG emulsion gel. A subsequent immersion within an alkaline solution imitating the small intestine fluid (yet without digestive enzymes) reduced the dynamic moduli of both kinds of emulsion gels. The alkaline immersion also caused extensive crack propagation in LaG emulsion gel network, which was found associated with diminished value of tan δ (G''/G') as an index of gel energy dissipation. Lipase was released form LaG emulsion gel into the alkaline solution, however, it took a remarkable period of time to begin.

Self-assembled tetrahedral DNA nanostructures-based ultrasensitive label-free detection of ampicillin.

Antibiotics are widely used for improving the living conditions of livestock. However, residual antibiotics present in animal products induce several human diseases. Therefore, a simple, rapid, and cost-effective system for detecting and monitoring the presence of antibiotics in foods is in great demand to alleviate safety concerns. In this study, a highly sensitive and selective aptameric electrochemical sensing platform was designed based on nanomaterial modification and DNA nanotechnology. Electrochemically reduced graphene oxide and gold nanoparticles were used to modify the working surface of a screen-printed electrode to enhance electrical conductivity and biocompatibility. The electrode surface was further modified with self-assembled tetrahedral DNA nanostructures (TDN) to improve the detection sensitivity. The TDN allowed controlling the nano-spacing of aptamers immobilized on the electrode surface and placing aptamers in a solution-phase-like detecting environment to improve the target-binding efficiency without signal amplification modules. Differential pulse voltammetry was employed to measure electrical signals in proportion to the amount of ampicillin, the target antibiotic, present in buffer and spiked milk samples. The designed aptasensor was able to detect and measure the target ampicillin in less than 30 min over a wide concentration range of 10 pM to 1 mM, with a limit of detection of 1 pM, which is 100 times better than when using the same sensing probe without TDN modification. The aptasensor was reusable by simply rinsing with deionized water, remained stable during 15-day storage, and yielded reproducible results.

Oxygen-terminated few-layered Ti3C2Tx MXene nanosheets as peroxidase-mimic nanozyme for colorimetric detection of kanamycin.

Nanomaterials-based bioinspired enzyme mimics are gaining increased attention as alternatives to biocatalysts. Herein, we report synthesizing oxygen-terminated few-layered titanium-based MXene nanosheets (OFL-Ti-MN). OFL-Ti-MN possesses horseradish peroxidase (HRP) activity in catalyzing the oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2), which turns the solution color bluish-green. The solution color fades quickly when kanamycin (KAN) is added to this system. This reaction indicates that KAN can prevent color change in the OFL-Ti-MN/TMB-H2O2 system. Based on this strategy, we developed an OFL-Ti-MN-based colorimetric sensor to detect and quantify KAN. The sensor exhibited a dynamic range from 15.28 nM to 46.14 µM and a calculated limit of detection (LOD) of 15.28 nM. From the insight gained from the peroxidase-mimic property of OFL-Ti-MN, we proposed a mechanism for the inhibition effect of KAN on peroxidase and peroxidase-mimic enzymes. The proposed mechanism can potentially help elucidate the reasons for the antibacterial function of KAN and its side effects in humans.

Cranberry proanthocyanidins composite electrospun nanofibers as a potential alternative for bacterial entrapment applications.

The interaction between A-type interflavan bonds from cranberry proanthocyanidins (PAC) and surface virulence factors of extra-intestinal pathogenic Escherichia coli (ExPEC) was studied. Electrospun nanofibers (ESNF) were fabricated using PAC and polycaprolactone (PCL) solutions and their physical and chemical properties were characterized. The ability of PAC:PCL composite ESNF to interact with and entrap ExPEC strain 5011 (ExPEC-5011) was evaluated in vitro by plate culturing and when formulated as a biofilter and nanocoating. As a biofilter, the PAC:PCL ESNF exhibited a dose-dependent ability to entrap ExPEC-5011. Images from scanning electron and fluorescent microscopies revealed that ESNF sections with higher amounts of PAC led to higher bacterial entrapment. The effectiveness PAC:PCL ESNF to bind ExPEC when applied as a nanocoating was studied using ESNF-coated polyvinyl chloride intermittent catheter. Results indicate that ExPEC-5011 was entrapped well into the PAC:PCL ESNF coating on the catheter. Overall, our results suggest that incorporating the biomolecule PAC in ESNF is a potential means for applications requiring bacterial entrapment, such as biofunctionalization, biofiltration, and surface coating, among others.

Cranberry Proanthocyanidins-PANI Nanocomposite for the Detection of Bacteria Associated with Urinary Tract Infections.

Consumption of cranberries is associated with the putative effects of preventing urinary tract infections (UTIs). Cranberry proanthocyanidins (PAC) contain unusual double A-type linkages, which are associated with strong interactions with surface virulence factors found on UTI-causing bacteria such as extra-intestinal pathogenic Escherichia coli (ExPEC), depicting in bacterial agglutination processes. In this work, we demonstrated the efficacy of cranberry PAC (200 µg/mL) to agglutinate ExPEC (5.0 × 108 CFU/mL) in vitro as a selective interaction for the design of functionalized biosensors for potential detection of UTIs. We fabricated functionalized screen-printed electrodes (SPEs) by modifying with PAC-polyaniline (PANI) nanocomposites and tested the effectiveness of the PAC-PANI/SPE biosensor for detecting the presence of ExPEC in aqueous suspensions. Results indicated that the PAC-PANI/SPE was highly sensitive (limit of quantification of 1 CFU/mL of ExPEC), and its response was linear over the concentration range of 1-70,000 CFU/mL, suggesting cranberry PAC-functionalized biosensors are an innovative alternative for the detection and diagnosis of ExPEC-associated UTIs. The biosensor was also highly selective, reproducible, and stable.

Comparative efficacy of biogenic zinc oxide nanoparticles synthesized by Pseudochrobactrum sp. C5 and chemically synthesized zinc oxide nanoparticles for catalytic degradation of dyes and wastewater treatment.

Discharge of untreated textile wastewaters loaded with dyes is not only contaminating the soil and water resources but also posing a threat to the health and socioeconomic life of the people. Hence, there is a need to devise the strategies for effective treatment of such wastewaters. The present study reports the catalytic potential of biogenic ZnO nanoparticles (ZnO NPs) synthesized by using a bacterial strain Pseudochrobactrum sp. C5 for degradation of dyes and wastewater treatment. The catalytic potential of the biogenic ZnO NPs for degradation of dyes and wastewater treatment was also compared with that of the chemically synthesized ones. The characterization of the biogenic ZnO NPs through FT-IR, XRD, and field emission scanning electron microscopy (FESEM) indicated that these are granular agglomerated particles having a size range of 90-110 nm and zeta potential of -27.41 mV. These catalytic NPs had resulted into almost complete (> 90%) decolorization of various dyes including the methanol blue and reactive black 5. These NPs also resulted into a significant reduction in COD, TDS, EC, pH, and color of two real wastewaters spiked with reactive black 5 and reactive red 120. The findings of this study suggest that the biosynthesized ZnO NPs might serve as a potential green solution for treatment of dye-loaded textile wastewaters.

FEAST of biosensors: Food, environmental and agricultural sensing technologies (FEAST) in North America.

We review the challenges and opportunities for biosensor research in North America aimed to accelerate translational research. We call for platform approaches based on: i) tools that can support interoperability between food, environment and agriculture, ii) open-source tools for analytics, iii) algorithms used for data and information arbitrage, and iv) use-inspired sensor design. We summarize select mobile devices and phone-based biosensors that couple analytical systems with biosensors for improving decision support. Over 100 biosensors developed by labs in North America were analyzed, including lab-based and portable devices. The results of this literature review show that nearly one quarter of the manuscripts focused on fundamental platform development or material characterization. Among the biosensors analyzed for food (post-harvest) or environmental applications, most devices were based on optical transduction (whether a lab assay or portable device). Most biosensors for agricultural applications were based on electrochemical transduction and few utilized a mobile platform. Presently, the FEAST of biosensors has produced a wealth of opportunity but faces a famine of actionable information without a platform for analytics.

Ultrathin quasi-hexagonal gold nanostructures for sensing arsenic in tap water.

Monodispersed colloidal gold nanoparticles (AuNPs) were synthesized by an easy, cost-effective, and eco-friendly method. The AuNPs were mostly quasi-hexagonal in shape with sizes ranging from 15 to 18 nm. A screen-printed electrode modified with AuNPs (AuNPs/SPE) was used as an electrochemical sensor for the detection of As(iii) in water samples. The mechanistic details for the detection of As(iii) were investigated and an electrochemical reaction mechanism was proposed. Under the optimal experimental conditions, the sensor was highly sensitive to As(iii), with a limit of detection of 0.11 µg L-1 (1.51 nM), which is well below the regulatory limit of 10 µg L-1 established by the United States Environmental Protection Agency and the World Health Organization. The sensor responses were highly stable, reproducible, and linear over the As(iii) concentration range of 0.075 to 30 µg L-1. The presence of co-existing heavy metal cations such as lead, copper, and mercury did not interfere with the sensor response to As(iii). Furthermore, the voltammogram peaks for As(iii), lead, copper, and mercury were sufficiently separate for their potential simultaneous measurement, and at very harsh acidic pH it may be possible to detect As(v). The AuNPs/SPE could detect As(iii) in tap water samples at near-neutral pH, presenting potential possibilities for real-time, practical applications.

Ultrasensitive electrochemical genosensor for detection of CaMV35S gene with Fe3O4-Au@Ag nanoprobe.

We report an attomolar sensitive electrochemical genosensor for the detection of cauliflower mosaic virus 35S (CaMV35S) gene. The sandwich-type genosensor uses gold-silver core-shell (Au@Ag)-loaded iron oxide (Fe3O4) nanocomposite (Fe3O4-Au@Ag) as label of signal DNA probe (sDNA). Electrochemical sensing is accomplished at interface of electrodeposited AuNPs and carboxylated multiwalled carbon nanotubes-modified glassy carbon electrode through the specific interaction between the capture probe and target CaMV35S (tDNA), and tDNA and the labeled sDNA. The detection sensitivity was improved by the amplified reduction signal of hydrogen peroxide (H2O2), which takes advantage of the enhanced electrocatalytic activity of Fe3O4-Au@Ag. Under the optimal experimental conditions, an ultralow limit of detection was calculated to be 1.26 × 10-17 M (S/N = 3), and the blank value subtracted reduction signal of H2O2 of the sensor increased linearly with the logarithm of CaMV35S concentration over a wide range (1 × 10-16 M to 1 × 10-10 M). This genosensor displayed excellent stability, selectivity and reproducibility, and was successful in detecting the target CaMV35S in genetically modified tomato samples.

Experimental data on the production and characterization of biochars derived from coconut-shell wastes obtained from the Colombian Pacific Coast at low temperature pyrolysis.

Biochars are emerging eco-friendly products showing outstanding properties in areas such as carbon sequestration, soil amendment, bioremediation, biocomposites, and bioenergy. These interesting materials can be synthesized from a wide variety of waste-derived sources, including lignocellulosic biomass wastes, manure and sewage sludge. In this work, abundant data on biochars produced from coconut-shell wastes obtained from the Colombian Pacific Coast are presented. Biochar synthesis was performed varying the temperature (in the range: 280 °C-420 °C) and O2 feeding (in the range: 0-5% v/v) in the pyrolysis reaction. Production yields and some biochar properties such as particle size, Zeta Potential, elemental content (C, N, Al, B, Ca, Cu, Fe, K, Li, Mg, Mn, Na, P, S, Ti, Zn), BET surface area, FT-IR spectrum, XRD spectrum, and SEM morphology are presented. This data set is a comprehensive resource to gain a further understanding of biochars, and is a valuable tool for addressing the strategic exploitation of the multiple benefits they have.

Dual-channel ITO-microfluidic electrochemical immunosensor for simultaneous detection of two mycotoxins.

Due to the widely occurring co-contamination of mycotoxins in raw food materials, simultaneous monitoring of multiple mycotoxins is needed. Herein, we report the design and fabrication of an electrochemical immunosensor for simultaneous detection of two mycotoxins, fumonisin B1 (FB1) and deoxynivalenol (DON), in a single test. A dual-channel three-electrode electrochemical sensor pattern was etched on a transparent indium tin oxide (ITO)-coated glass via photolithography and was integrated with capillary-driven polydimethylsiloxane (PDMS) microfluidic channel. The two working electrodes were functionalized with gold nanoparticles and anti-FB1 and anti-DON antibodies. Tests were performed by incubating the working electrodes in a sample solution introduced in the PDMS channel. The formation of toxin-antibody immunocomplexes on the working electrode surface produced electrochemical signal responses, which were recorded and compared with control signal to quantify individual mycotoxin concentrations. Using this dual-channel ITO-microfluidic electrochemical immunosensor we achieved limits of detection (LODs) of 97 pg/mL and 35 pg/mL, respectively for FB1 and DON, and their corresponding linear ranges of detection were 0.3-140 ppb and 0.2-60 ppb. The sensor performance, which remained stable for two weeks under proper storage, was validated by testing with ground corn extract used as a real food matrix.

Atomic force microscopy-based cancer diagnosis by detecting cancer-specific biomolecules and cells.

Atomic force microscopy (AFM) has recently attracted much attention due to its ability to analyze biomolecular interactions and to detect certain biomolecules, which play a crucial role in disease expression. Despite recent studies reporting AFM imaging for the analyses of biomolecules, the application of AFM-based cancer-specific biomolecule/cell detection has remained largely underexplored, especially for the early diagnosis of cancer. In this paper, we review the recent attempts, including our efforts, to analyze and detect cancer-specific biomolecules and cancer cells. We particularly focus on two AFM-based cancer diagnosis techniques: (i) AFM imaging-based biomolecular and cellular detection, (ii) AFM cantilever-based biomolecular sensing and cell analysis. It is shown that AFM-based biomolecular detection has been applied for not only early diagnosing cancer, by measuring the minute amount of cancer-specific proteins, but also monitoring of cancer progression, by correlating the amount of cancer-specific proteins with the progression of cancer. In addition, AFM-based cell imaging and detection have been employed for diagnosing cancer, by detecting cancerous cells in tissue, as well as understanding cancer progression, by characterizing the dynamics of cancer cells. This review, therefore, highlights AFM-based biomolecule/cell detection, which will pave the way for developing a fast and point-of-care diagnostic system for biomedical applications.

Synthesis of Positively and Negatively Charged CeO2 Nanoparticles: Investigation of the Role of Surface Charge on Growth and Development of Drosophila melanogaster.

Monodispersed cerium oxide nanoparticles (CeO2 NPs) with positive and negative surface potential were synthesized by co-precipitation method using hexamethylenetetramine (HMT) and poly(vinylpyrrolidone) (PVP), respectively, as precipitating agents. Synthesized NPs were characterized with scanning electron microscopy (SEM), UV-Visible (UV-Vis) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, and powder X-ray diffraction (XRD). Positively charged NPs of about 30 ± 10 nm in size formed within 5 h, aggregated in number, and resulted in larger-sized NPs as a function of time. The CeO2 NPs were administered to Drosophila as a part of their diet to study the effects on the growth and development of Drosophila. While the positively charged NPs did not affect the growth of the third instar larvae, the negatively charged NPs delayed the growth of larvae by about 7 days. It required 7 more days to reach the stage of adult fly. TEM imaging of the larvae gut showed that positively charged NPs were found to be smaller, whereas the size of negatively charged NPs remained unchanged. This biodegradability could be the reason for the delayed larvae growth in the case of negatively charged particles. The distance covered by such second instar larvae fed with diet containing negatively charged CeO2 NPs was significantly lower, and their size was significantly smaller when compared to the crawling activity and size of the third instar larvae of the control group. Such positively charged NPs have high potential for use as drug delivery carriers for the treatment of disease, and negatively charged NPs may play a rather detrimental role.