Ultrasensitive NIR fluorometric assay for inorganic pyrophosphatase detection via Cu2+-PPi interaction using bimetallic Au-Ag nanoclusters.

BACKGROUND: Inorganic pyrophosphatase (PPase) is key enzyme playing a key role in biochemical transformations such as biosynthesis of DNA and RNA, bone formation, metabolic pathways associated with lipid, carbohydrate and phosphorous. It has been reported that lung adenocarcinomas, colorectal cancer, and hyperthyroidism disorders can result from abnormal level of PPase. Therefore, it is of notable significance to develop simple and effective real time assay for PPase enzyme activity monitoring for screening of many metabolic pathways as well as for early disease diagnosis. RESULT: The fluorometric detection of PPase enzyme in near infrared region-1 (NIR-1) has been carried out using bimetallic nanoclusters (LA@AuAg NCs). The developed sensing strategy was based on quenching of fluorescence intensity of LA@AuAg NCs upon interaction with copper (Cu2+) ions. The off state of LA@AuAg_Cu2+ ensemble was turned on upon addition of pyrophosphate anion (PPi) due to strong binding interaction between PPi and Cu2+. The catalytic conversion of PPi into phosphate anion (Pi) in the presence of PPase led to liberation of Cu2+ ions, and again quenched off state was retrieved due to interaction of free Cu2+ with LA@AuAg NCs. The ultrasensitive detection of PPase was observed in the linear range of 0.06-250 mU/mL with LOD as 0.0025 mU/mL. The designed scheme showed good selectivity towards PPase enzyme in comparison to other bio-substrates, along with good percentage recovery for PPase detection in real human serum samples. SIGNIFICANCE: The developed NIR based assay is ultrasensitive, highly selective and robust for PPase enzyme and can be safely employed for other enzymes detection. This highly sensitive nature of biosensor was result of involvement of fluorescence-based technique and synergistic effect of dual metal in NIR based bimetallic NCs. Moreover, owing to the emission in NIR domain, in future, these nanoclusters can be safely employed for many biomedical applications for In vivo studies.

Chitosan functionalized doxorubicin loaded poly(methacrylamide) based copolymeric nanoparticles for enhanced cellular internalization and in vitro anticancer evaluation.

Doxorubicin (Dox), a chemotherapeutic agent, encounters challenges such as a short half-life, dose-dependent toxicity, and low solubility. In this context, the present study involved the fabrication of N-(2-hydroxypropyl)methacrylamide (HPMA) and N-(3-aminopropyl)methacrylamide (APMA) bearing P(HPMA-s-APMA) copolymeric nanoparticles (P(HPMA-s-APMA) NPs) and their investigation for efficient delivery of Dox. Furthermore, the synthesized nanoparticles (NPs) were coated with chitosan (Cht) to generate positively charged nanoformulations. The prepared formulations were evaluated for particle size, morphology, surface charge analysis, percentage encapsulation efficiency (EE%), and drug release studies. The anticancer activity of Cht-P(HPMA-s-APMA)-Dox NPs was assessed in the HeLa cancer cell line. The prepared P(HPMA-s-APMA)-Dox NPs exhibited an average particle size of 240-250 nm. Chitosan decorated P(HPMA-s-APMA)-Dox NPs displayed a significant increase in particle size, and the zeta potential shifted from negative to positive. The EE% for Cht-P(HPMA-s-APMA)-Dox NPs was calculated to be 68.06 %. The drug release studies revealed a rapid release of drug from Cht-P(HPMA-s-APMA)-Dox NPs at pH 4.8 than pH 7.4, demonstrating the pH-responsiveness of nanoformulation. Furthermore, the cell viability assay and internalization studies revealed that Cht-P(HPMA-s-APMA)-Dox NPs had a high cytotoxic response and significant cellular uptake. Hence, the Cht-P(HPMA-s-APMA)-Dox NPs appeared to be a suitable nanocarrier for effective, and safe chemotherapy.

Exploring the potential of radiolabeled duramycin as an infection imaging probe.

The continuous pursuit of designing an ideal infection imaging agent is a crucial and ongoing endeavor in the field of biomedical research. Duramycin, an antimicrobial peptide exerts its antimicrobial action on bacteria by specific recognition of phosphatidylethanolamine (PE) moiety present on most bacterial membranes, particularly Escherichia coli (E. coli). E. coli membranes contain more than 60% PE. Therefore, duramycin is an attractive candidate for the formulation of probes for in situ visualization of E. coli driven focal infections. The aim of the present study is to develop 99m Tc labeled duramycin as a single-photon emission computed tomography (SPECT)-based agent to image such infections. Duramycin was successfully conjugated with a bifunctional chelator, hydrazinonicotinamide (HYNIC). PE specificity of HYNIC-duramycin was confirmed by a dye release assay on PE-containing model membranes. Radiolabeling of HYNIC-duramycin with 99m Tc was performed with consistently high radiochemical yield (>90%) and radiochemical purity (>90%). [99m Tc]Tc-HYNIC-duramycin retained its specificity for E. coli, in vitro. SPECT and biodistribution studies showed that the tracer could specifically identify E. coli driven infection at 3 h post injection. While 99m Tc-labeled duramycin is employed for monitoring early response to cancer therapy and cardiotoxicity, the current studies have confirmed, for the first time, the potential of utilizing 99m Tc labeled duramycin as an imaging agent for detecting bacteria. Its application in imaging PE-positive bacteria represents a novel and promising advancement.

Investigating the Role of Classical Ayurveda-Based Incineration Process on the Synthesis of Zinc Oxide Based Jasada Bhasma Nanoparticles and Zn2+ Bioavailability.

Jasada bhasma (JB) is a zinc oxide-based Indian traditional Ayurveda-based herbo-metallic nanoparticle used for the treatment of zinc (Zn) deficiency and autoimmune and inflammatory disorders. JB is made by following the Ayurveda-based guidelines using zinc oxide (ZnO) as a raw material and going through 17 cycles of the high-temperature incineration and trituration process known as "Ma̅rana" in the presence of herbal decoctions prepared from the leaves ofAzadirachta indica andAloe vera gel. These cycles improve the purity of the parent material and transform its physicochemical properties, converting it into nanoparticles. However, there still exists a knowledge gap regarding the role of incineration in the physicochemical transformation of the Zn raw material into JB nanoparticles and the biological interaction of the final product. In the present study, the JB samples obtained during different Ma̅rana cycles were carefully studied for their physicochemical transformation using analytical methods such as powdered X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and dynamic light scattering (DLS). According to the XRD results, the Zn and oxygen molecules in hexagonal ZnO wurtzite crystals gradually realigned as a result of repeated heat treatments that caused lattice tension and crystal size reduction from 53.14 to 42.40 nm. A morphological transition from 1.5 µm rod shape to 31 nm in the JB particles can be seen using FESEM and SAXS analyses. The existence of 10 nm-sized nanoparticles in the finished product was confirmed by HRTEM. The presence of ZnO was confirmed in all samples by FTIR and Raman spectroscopies. Cell viability analysis showed an inhibitory concentration 50% of >1000 µg/mL for JB nanoparticles, revealing no adverse effects in human colon Caco-2 cells. A dose-dependent uptake and intracellular accumulation of JB nanoparticles were observed in Caco-2 cells using inductively coupled plasma-based mass spectroscopy (ICP-MS). Bioavailability of Zn2+ ions (6% w/w) through JB dissolution in acidic pH 4.0 was observed, representing the stomach and intracellular lysosomal physiological conditions. Therefore, the study showed that the repeated incineration cycles produced biocompatible JB nanoparticles through the physicochemical transformation at molecular levels capable of delivering bioavailable Zn2+ ions under physiological conditions. In conclusion, the medicinal properties of JB nanoparticles described in Ayurveda were found to originate from their small size and dissolution properties, formed through the classical incineration-based synthesis process.

Targeting bacterial biofilms using vancomycin and multivalent cell-penetrating peptide labeled quantum dots.

Bacterial biofilms are highly resilient microbial musters that are difficult to eradicate, driving the development of novel therapeutic strategies. The current study aims to investigate the therapeutic efficacy of cell-penetrating peptide-based targeted delivery of vancomycin functionalized quantum dots in eradicating biofilm formation in gram-positive and gram-negative bacterial strains. The conjugate was characterized using fluorimetry, UV-visible spectroscopy, gel electrophoresis, and zeta potential. The conjugate was then tested for antimicrobial and antibiofilm activity against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli, and it demonstrated excellent antimicrobial as well as antibiofilm activity against all the tested strains. The findings indicated that the conjugate was capable of overcoming bacterial resistance of bacteria in addition to the eradication of biofilms at effective concentrations.

Femtomolar detection of staphylococcal enterotoxin 'B' using a fluorescent quantum dot based hybrid Apta-immunosensor.

Food poisoning is a gastrointestinal illness caused by food-borne enterotoxin produced by the bacterium Staphylococcus aureus. The effective dose of Staphylococcal enterotoxin 'B' (SEB) is estimated to be 0.4 ng/kg of body weight, whereas the 50 % lethal dose is found to be 20 ng/kg of body weight for humans exposed by the inhalation route. The present report highlights the development of a fluorescence resonance energy transfer (FRET) based assay for the detection of Staphylococcal enterotoxin. Highly fluorescent, aqueous quantum dots were synthesized and conjugated with Staphylococcal enterotoxin 'B' specific bioreceptors. SEB specific aptamer and SEB antibody were labeled with fluorescent quantum dots for recognizing and binding two separate epitopes in the SEB. A combination of two probes against different epitopic regions in a homogeneous sandwich assay format enhanced the sensitivity and specificity of SEB detection. In the presence of the enterotoxin, both the aptamer and antibody came in close proximity with each other and FRET was observed. A linear decrease in the fluorescence at 562 nm and a corresponding increase in the signal at 644 nm was observed with increasing concentrations of SEB, when excited at the absorption maximum of quantum dots. The limit of detection for the developed assay obtained was less than 1 ng/ml. The method was employed in apple juice and quantitated using Enzyme-linked Immunosorbent Assay (ELISA). The designed assay was rapid and robust and can be extrapolated as a platform for the detection of various disease-causing agents of biomedical significance.

Ultrasensitive aptasensor for arsenic detection using quantum dots and guanylated Poly(methacrylamide).

The present study demonstrate the first time usage of poly (HPMA-s-GPMA) copolymer for the fabrication of three-component based aptasensor for simple, selective, rapid and label free detection of arsenite (As3+). For this purpose, guanidinium bearing poly (HPMA-s-GPMA) copolymer and MPA-CdTe@CdS quantum dots (QDs) was employed in conjunction with As3+ specific aptamer. This protocol utilizes the quenching phenomena displayed by QDs due to the competitive binding of As3+ ions and cationic copolymer to the aptamer. In particular, the As3+ bind to the specific aptamer, leaving poly (HPMA-s-GPMA) freely available for its electrostatic intercations with QDs, which quenches the fluorescent signal. Contrarily, in the absence of As3+ ions, the aptamer can electrostatically bind to poly (HPMA-s-GPMA); making copolymer inactive to affect the fluorescence signal of the QDs. The efficiency of the proposed fluorescence nanoprobe was further tested using linear calibration curves. The obtained data in the range of 0.01-100 nM showed excellent specificity for As3+ ions with the limit of detection (LOD) of 246.77 pM. Moreover, the "on-off" fluorescent aptasensor is highly selective for As3+ ions in the presence of other interfering metal ions by utilizing As3+ specific aptamer. Furthermore, the reported study showed outstanding applicability in the real-world samples (water, food and soil) containing preservatives, metal ions, minerals, and other moieties. The proposed sensing platform not only exhibits the trace level detection of As3+ ions in cost-effective manner but also opens a pathway for the development of state-of-art device fabrication for on-site detection of arsenic.

Reduced RBPMS Levels Promote Cell Proliferation and Decrease Cisplatin Sensitivity in Ovarian Cancer Cells.

Worldwide, the number of cancer-related deaths continues to increase due to the ability of cancer cells to become chemotherapy-resistant and metastasize. For women with ovarian cancer, a staggering 70% will become resistant to the front-line therapy, cisplatin. Although many mechanisms of cisplatin resistance have been proposed, the key mechanisms of such resistance remain elusive. The RNA binding protein with multiple splicing (RBPMS) binds to nascent RNA transcripts and regulates splicing, transport, localization, and stability. Evidence indicates that RBPMS also binds to protein members of the AP-1 transcription factor complex repressing its activity. Until now, little has been known about the biological function of RBPMS in ovarian cancer. Accordingly, we interrogated available Internet databases and found that ovarian cancer patients with high RBPMS levels live longer compared to patients with low RBPMS levels. Similarly, immunohistochemical (IHC) analysis in a tissue array of ovarian cancer patient samples showed that serous ovarian cancer tissues showed weaker RBPMS staining when compared with normal ovarian tissues. We generated clustered regularly interspaced short palindromic repeats (CRISPR)-mediated RBPMS knockout vectors that were stably transfected in the high-grade serous ovarian cancer cell line, OVCAR3. The knockout of RBPMS in these cells was confirmed via bioinformatics analysis, real-time PCR, and Western blot analysis. We found that the RBPMS knockout clones grew faster and had increased invasiveness than the control CRISPR clones. RBPMS knockout also reduced the sensitivity of the OVCAR3 cells to cisplatin treatment. Moreover, ß-galactosidase (ß-Gal) measurements showed that RBPMS knockdown induced senescence in ovarian cancer cells. We performed RNAseq in the RBPMS knockout clones and identified several downstream-RBPMS transcripts, including non-coding RNAs (ncRNAs) and protein-coding genes associated with alteration of the tumor microenvironment as well as those with oncogenic or tumor suppressor capabilities. Moreover, proteomic studies confirmed that RBPMS regulates the expression of proteins involved in cell detoxification, RNA processing, and cytoskeleton network and cell integrity. Interrogation of the Kaplan-Meier (KM) plotter database identified multiple downstream-RBPMS effectors that could be used as prognostic and response-to-therapy biomarkers in ovarian cancer. These studies suggest that RBPMS acts as a tumor suppressor gene and that lower levels of RBPMS promote the cisplatin resistance of ovarian cancer cells.

Iron Chelator Transmetalative Approach to Inhibit Human Ribonucleotide Reductase.

Efforts directed at curtailing the bioavailability of intracellular iron could lead to the development of broad-spectrum anticancer drugs given the metal's role in cancer proliferation and metastasis. Human ribonucleotide reductase (RNR), the key enzyme responsible for synthesizing the building blocks of DNA replication and repair, depends on Fe binding at its R2 subunit to activate the catalytic R1 subunit. This work explores an intracellular iron chelator transmetalative approach to inhibit RNR using the titanium(IV) chemical transferrin mimetic (cTfm) compounds Ti(HBED) and Ti(Deferasirox)2. Whole-cell EPR studies reveal that the compounds can effectively attenuate RNR activity though seemingly causing different changes to the labile iron pool that may account for differences in their potency against cells. Studies of Ti(IV) interactions with the adenosine nucleotide family at pH 7.4 reveal strong metal binding and extensive phosphate hydrolysis, which suggest the capacity of the metal to disturb the nucleotide substrate pool of the RNR enzyme. By decreasing intracellular Fe bioavailability and altering the nucleotide substrate pool, the Ti cTfm compounds could inhibit the activity of the R1 and R2 subunits of RNR. The compounds arrest the cell cycle in the S phase, indicating suppressed DNA replication, and induce apoptotic cell death. Cotreatment cell viability studies with cisplatin and Ti(Deferasirox)2 reveal a promising synergism between the compounds that is likely owed to their distinct but complementary effect on DNA replication.

Targeting Non-coding RNA for Glioblastoma Therapy: The Challenge of Overcomes the Blood-Brain Barrier.

Glioblastoma (GBM) is the most malignant form of all primary brain tumors, and it is responsible for around 200,000 deaths each year worldwide. The standard therapy for GBM treatment includes surgical resection followed by temozolomide-based chemotherapy and/or radiotherapy. With this treatment, the median survival rate of GBM patients is only 15 months after its initial diagnosis. Therefore, novel and better treatment modalities for GBM treatment are urgently needed. Mounting evidence indicates that non-coding RNAs (ncRNAs) have critical roles as regulators of gene expression. Long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) are among the most studied ncRNAs in health and disease. Dysregulation of ncRNAs is observed in virtually all tumor types, including GBMs. Several dysregulated miRNAs and lncRNAs have been identified in GBM cell lines and GBM tumor samples. Some of them have been proposed as diagnostic and prognostic markers, and as targets for GBM treatment. Most ncRNA-based therapies use oligonucleotide RNA molecules which are normally of short life in circulation. Nanoparticles (NPs) have been designed to increase the half-life of oligonucleotide RNAs. An additional challenge faced not only by RNA oligonucleotides but for therapies designed for brain-related conditions, is the presence of the blood-brain barrier (BBB). The BBB is the anatomical barrier that protects the brain from undesirable agents. Although some NPs have been derivatized at their surface to cross the BBB, optimal NPs to deliver oligonucleotide RNA into GBM cells in the brain are currently unavailable. In this review, we describe first the current treatments for GBM therapy. Next, we discuss the most relevant miRNAs and lncRNAs suggested as targets for GBM therapy. Then, we compare the current drug delivery systems (nanocarriers/NPs) for RNA oligonucleotide delivery, the challenges faced to send drugs through the BBB, and the strategies to overcome this barrier. Finally, we categorize the critical points where research should be the focus in order to design optimal NPs for drug delivery into the brain; and thus move the Oligonucleotide RNA-based therapies from the bench to the clinical setting.

Sensing platform for pico-molar level detection of ethyl parathion using Au-Ag nanoclusters based enzymatic strategy.

This work demonstrates a simple, cost effective and ultrasensitive detection of ethyl parathion, an organophosphorus (OPs) pesticide, using enzyme based fluorometric sensing strategy by employing bimetallic BSA@AuAg nanoclusters (NC). The sensing assay is based on the "quenched off" state of bimetallic NC with the addition of Cu2+ ions that can be "switched on" due to generation of thiocholine (TCh), a catalytic product of enzymatic reaction of acetylthiocholine (ATCh) using acetylcholinesterase (AChE) enzyme. The generated TCh preferably seize Cu2+ ions from BSA@AuAg NC-Cu2+ ensemble and recovered the fluorescence of BSA@AuAg NC. The presence of ethyl parathion can be monitored optically due to its inhibitory action towards AChE enzyme leading to suppression of thiocholine (TCh) formation and subsequently decreases TCh-Cu2+ interaction that ultimately retrieved quenched off state of bimetallic NC. The synthesized biosensor is appropriate for the ultrasensitive sensing of ethyl parathion in pM range, exhibiting 2.40 pM as lowest limit of detection (LOD) which is the least known so far. Further, the real sample analysis adds on for the appropriateness of the synthesized nanoprobe by depicting excellent reproducibility and robustness. The designed assay proved its specificity towards pesticides in general and ethyl parathion in particular when employed with other commonly used non-OPs pesticides.

Quantification of adsorbed and dangling citrate ions on gold nanoparticle surface using thermogravimetric analysis.

A novel approach involving thermo-gravimetricanalysis (TGA) for the quantification of citrate ions present on the surface of gold nanoparticles has been reported. TGA study was carried out on AuNPs in response to parameters such as concentration of tri-sodium citrate and pH of gold nanoparticles depicting that the number of citrate ion present on gold nanoparticles is highly pH dependent. In general, the citrate ions were observed to be higher in alkaline conditions contradicting earlier beliefs. These results also underline the significance of TGA as a novel tool for quantification of citrate molecules present on gold nanoparticle surface. Thus, the present approach not only provides with an insight into mechanistic details of gold nanoparticle synthesis but also opens the usage of TGA for understanding the nano range association of molecules.

Phenylalanine dimer assembly structure as the basic building block of an amyloid like photoluminescent nanofibril network.

A phenylalanine dimer assembly (Phe-DA) is reported as a basic constituent of a light emitting ß-amyloid type nanofibril network. The size and composition of the Phe-DA structure were characterized using various theoretical and experimental techniques. Further, the mechanism involved in the phenylalanine self-assembly process from Phe-DA to the nanofibril network was studied using optical spectroscopy and small angle X-ray scattering (SAXS). The discovery of Phe-DA and its unique optical properties may pave the way for design and development of novel theranostics against metabolite based pathalogical disorders. Further, the role of the Phe-DA structure as the elementary unit in the formation of a long range assembly structure may provide vital understanding for the development of functional materials using simple organic molecules.

Interplay of Self-Assembling Aromatic Amino Acids and Functionalized Gold Nanoparticles Generating Supramolecular Structures.

In the recent years, protein metabolite-based self-assembled supramolecular structures have been linked to various pathological disorders. The self-assembly of protein over nanoparticle surfaces can lead to the formation of corona aggregates that have gained much attention owing to biomedical healthcare relevance. However, limited studies are available at the interface of amyloid formation and nanoparticle surfaces. In this context, the present study demonstrated the effect of specifically functionalized gold nanoparticles on the potential amyloid formation by self-assembled aromatic amino acids. The coassembly of aromatic amino acids and gold nanoparticles was utilized to gain mechanistic insight into altered intermolecular interactions between amino acid monomers. The polymorphism, thermal stability, and morphological pattern of coassembled aromatic amino acids and gold nanoparticle (Co-AA:AuNP) structures were analyzed using X-ray diffraction, thermogravimetric analysis, and field emission scanning electron microscopy, respectively. Finally, amyloid like aggregation of Co-AA:AuNP structures were evaluated using thioflavin T fluorescence assay in solution as well as the deposited phase. The present work is crucial for the design and usage of nanoparticles in biomedical applications, which may trigger amyloid-like metabolite aggregation leading to pathological disorders.

Peptide- and Drug-Functionalized Fluorescent Quantum Dots for Enhanced Cell Internalization and Bacterial Debilitation.

This report illustrates a strategy for designing a nanoconjugate derived vector that efficiently delivers antimicrobial drug directly into bacterial cells. The nanoconjugate comprises of negatively charged CDTe@CdS quantum dots (QDs) with its surface functionalized using cationic BP-100 (KKLFKKILKYL-amide), a known cell-penetrating peptide (CPP), via electrostatic approach. The interactions between QD and CPP in QD-functionalized CPPs (QD-CPP) have been well analyzed using fluorescence spectroscopy, gel electrophoresis, and ζ-potential analysis. The QD-CPP conjugate was internalized into Gram negative (Escherichia coli) as well as Gram positive (Staphylococcus aureus) bacterial strains with confocal studies exhibiting a strong signal in tested microorganisms. Further, to check the applicability of QD-CPP conjugate as a delivery vector for generating an effective therapeutics, ampicillin molecules were conjugated on QD-CPP surface to generate QD-CPP-Amp conjugate. The CPP and drug molecules on the surface of QDs were well quantified using high-performance liquid chromatography (HPLC) data. It was observed that the internalization and bacterial debilitation of the QD-CPP-Amp conjugate is 2- to 4-fold effective as compared to that of bare ampicillin. The morphological changes to the bacterial cells upon the treatment with QD-CPP-Amp conjugates were noted with no cytotoxic effect on tested mammalian cell lines. The results inferred that the proposed QD-CPP vector provides a targeted and proficient approach for cellular internalization of cargo (drug) in bacterial cells with effective tracking through florescent QDs.

Enhanced and selective adsorption of cationic dyes using novel biocompatible self-assembled peptide fibrils.

Herein, bio-compatible self-assembled peptide fibrils have been developed for adsorption of organic pollutants for water remediation with high adsorption capacity. The different morphological motifs of self-assembled dipeptide Fmoc-FW-OMe was formulated using solvent modulation which was characterized by optical microscopy, SEM, XRD and FT-IR. Specifically, the fibril structures were used for selective adsorption of cationic dyes from aqueous solutions with exceptional adsorption capacity noted for crystal violet (625 mg/g). To understand the mechanism of dye adsorption, kinetics studies and adsorption isotherm studies were carried out which proved that the adsorption follows second order kinetics and Langmuir adsorption isotherm. The pH studies suggested that the adsorption of dye is much higher in alkaline conditions as compared to acidic conditions. The self-assembled peptide fibrils showed high reusability over five cycles with negligible effect on the dye adsorption capacity. Notably, this is the first report that discusses the application of self-assembled short peptide based fibrils for removal of dyes from waste water and in particular, it demonstrates the highest adsorption capacity reported for crystal violet dye so far. In general, this efficient capturing of dye pollutants with minimum usage of biocompatible adsorbents presents a simple and cost effective method for water remediation.

Optical pico-biosensing of lead using plasmonic gold nanoparticles and a cationic peptide-based aptasensor.

A novel biosensor for the rapid detection of lead ions employing the optical properties of AuNPs, a lead-specific aptamer and a cationic peptide has been demonstrated. The limit of detection of the biosensor was 98.7 pM, the lowest so far obtained using colorimetry.

Fueling a Hot Debate on the Application of TiO2 Nanoparticles in Sunscreen.

Titanium is one of the most abundant elements in the earth's crust and while there are many examples of its bioactive properties and use by living organisms, there are few studies that have probed its biochemical reactivity in physiological environments. In the cosmetic industry, TiO2 nanoparticles are widely used. They are often incorporated in sunscreens as inorganic physical sun blockers, taking advantage of their semiconducting property, which facilitates absorbing ultraviolet (UV) radiation. Sunscreens are formulated to protect human skin from the redox activity of the TiO2 nanoparticles (NPs) and are mass-marketed as safe for people and the environment. By closely examining the biological use of TiO2 and the influence of biomolecules on its stability and solubility, we reassess the reactivity of the material in the presence and absence of UV energy. We also consider the alarming impact that TiO2 NP seepage into bodies of water can cause to the environment and aquatic life, and the effect that it can have on human skin and health, in general, especially if it penetrates into the human body and the bloodstream.

Insights into cell penetrating peptide conjugated gold nanoparticles for internalization into bacterial cells.

Gold nanoparticles (AuNPs) functionalized with different biomolecules find extensive application in therapy, clinical diagnosis and biomedical imaging. Herein, two derivatives of TAT peptide with sequences YGRKKRRQRRR and YGRKKRRQRRR-(ß-ala)3-Cys-amide were conjugated with tannic acid capped gold nanoparticles which acted as a carrier for cell penetrating peptides (CPPs) into the bacterial cells. The interaction of YGRKKRRQRRR peptide with AuNPs was non-covalent in nature whereas YGRKKRRQRRR-(ß-ala)3-Cys-amide interacted covalently with the AuNPs due to presence of thiol group in cysteine which bind strongly to gold nanoparticles surface. Further, tannic acid functionalised AuNPs conjugated CPPs constructs were duly characterized using critical flocculation essay test, UV-visible and TEM. FITC was tagged over AuNPs-CPPs in order to study the intracellular distribution using confocal microscopy. The confocal results revealed that nanoconjugates (AuNP-CPPs) of 5 nm diameter exhibited strong fluorescent signal in Gram positive and Gram negative bacterial strains. The present method can also be used for the killing of bacterial cells using photo-thermal therapy and therefore can be highly useful for targeting multi-drug resistant bacteria.

A Facile Approach for Synthesis and Intracellular Delivery of Size Tunable Cationic Peptide Functionalized Gold Nanohybrids in Cancer Cells.

Peptide-based drug delivery systems have become a mainstay in the contemporary medicinal field, resulting in the design and development of better pharmaceutical formulations. However, most of the available reports employ tedious multiple reaction steps for the conjugation of bioactive cationic peptides with drug delivery vehicles. To overcome these limitations, the present work describes a one-step approach for facile and time efficient synthesis of highly cationic cell penetrating peptide functionalized gold nanoparticles and their intracellular delivery. The nanoconstruct was synthesized by the reduction of gold metal ions utilizing cell penetrating peptide (CPP), which facilitated the simultaneous synthesis of metal nanoparticles and the capping of the peptide over the nanoparticle surface. The developed nanoconstruct was thoroughly characterized and tested for intracellular delivery into HeLa cells. Intriguingly, a high payload of cationic peptide over gold particles was achieved, in comparison to conventional conjugation methods. Moreover, this method also provides the ability to control the size and peptide payload of nanoparticles. The nanoconstructs produced showed enhanced cancer cell penetration (µM) and significant cytotoxic effect compared to unlabeled gold nanoparticles. Therefore, this novel approach may also have significant future potential to kill intracellular hidden dreaded pathogens like the human immunodeficiency virus, Mycobacterium tuberculosis, and so forth.