Increase In Hydrodynamic Diameter Research Articles

Synthesis of gold nanoparticles coated with glucose oxidase using PVP as passive adsorption linkage

Gold nanoparticles (AuNPs) have great potential as biosensors for glucose detection due to their high sensitivity, as well as their extraordinary physical and chemical properties that improve compatibility with different biorecognition molecules, such as glucose oxidase (GOx). In this work the D-glucose quantification was determined by using the traditional technique based on biochemical reaction of GOx and AuNPs functionalized with polyvinylpirrolidone (PVP) polymer and the enzyme. The AuNPs-PVP-GOx nanocomplexes were characterized by ultraviolet-visible (UV-Visible), Infrared (FTIR), and Raman spectroscopies, as well as scanning electron microscopy (SEM), Z potential, dynamic light scattering (DLS), and thermogravimetry analysis (TGA). In general, these techniques showed significant differences after each functionalization stage with PVP and GOx, for instance it was observed: the presence of different functional groups, an increase of hydrodynamic diameter from 48.60 to 198.77 nm, a shift of the band absorption to larger wavelength, a change in the surface potential and weight loss, and in the morphology of the nanocomplex, which confirm the functionalization. In addition, the enzymatic activity of the AuNPs-PVP-GOx was confirmed through the detection of triiodide ions by UV-Visible spectrophotometry, coming from the oxidation reaction of iodide ions in the presence of H2O2. Furthermore, the nanocomplex synthesized by passive adsorption was evaluated as a possible biosensor for the quantification of D-glucose using a colorimetric assay, obtaining greater sensitivity than the traditional method. These findings indicate that PVP can be used as a linkage medium between AuNPs and GOx, which in turn can be used as a biosensor for the detection of D-glucose at low concentrations in biological fluids.

Thermoresponsive Core-cross-linked Nanoparticles from HA-b-ELP Diblock Copolymers.

Stabilization against the dilution-dependent disassembly of self-assembled nanoparticles is a requirement for in vivo application. Herein, we propose a simple and biocompatible cross-linking reaction for the stabilization of a series of nanoparticles formed by the self-assembly of amphiphilic HA-b-ELP block copolymers, through the alkylation of methionine residues from the ELP block with diglycidyl ether compounds. The core-cross-linked nanoparticles retain their colloidal properties, with a spherical core-shell morphology, while maintaining thermoresponsive behavior. As such, instead of a reversible disassembly when non-cross-linked, a reversible swelling of nanoparticles' core and increase of hydrodynamic diameter are observed with lowering of the temperature.

Hyaluronic acid functionalized citric acid dendrimer/UiO-66-COOH as a stable and biocompatible platform for daunorubicin delivery

This work aimed to prepare a new system for daunorubicin (DNR) delivery to improve therapeutic efficiency and decrease unwanted side effects. Typically, at first, a carboxylic acid functional group containing metal-organic framework (UiO-66-COOH) was synthesized in a simple way. Then, a third generation of citric acid dendrimer (CAD G3) was grown on it (UiO-66-COOH-CAD G3). Finally, the system was functionalized with pre-modified hyaluronic acid (UiO-66-COOH-CAD-HA). SEM analysis displayed that the synthesized particles have a spherical shape with an average particle size ranging from 260 to 280 nm. An increase in hydrodynamic diameter from 223 nm for UiO-66-COOH to 481 nm for UiO-66-COOH-CAD-HA is a sign of success in the performed reactions. Also, the average pore size was calculated at about 4.04 nm. The DNR loading efficiency of UiO-66-COOH-CAD-HA was evaluated at ∼74 % (DNR@UiO-66-COOH-CAD-HA). It was observed that the drug release rate at a lower pH is more than higher pH. The maximum hemolysis of <3 % means that the UiO-66-COOH-CAD-HA is hemocompatible. The use of DNR-loaded UiO-66-COOH-CAD-HA led to cell-killing of 77.9 % for MDA-MB 231. These results specified the great potential of UiO-66-COOH-CAD-HA for tumor drug delivery, so it could be proposed as a new carrier for anticancer agents to minimize adverse effects and improve therapeutic efficacy.

Controlling cisplatin release by synergistic action of silver-cisplatin on monodispersed spherical silica for targeted anticancer and antibacterial activities

Recently, metal-based nanoformulations have been explored for targeted cancer therapeutics. In this study, synergistic therapeutic action of silver (Ag)-cisplatin nanoparticles loaded on monodispersed spherical silica (MSS) was investigated to evaluate anti-cancer (HCT-116 and HeLa cells) and antibacterial activity (P.aeruginosa, and S.aureus). Four different wt% of Ag (1, 2, 4 and 6 wt%) was loaded on MSS using a wet impregnation method. Characterization using XRD revealed the cubic phase of Ag nanoparticles with (111), (200) and (220) plane on MSS. The chemical state, dispersion of Ag and synergistic cohabitation with cisplatin (Cpt) was identified using diffuse reflectance UV–visible spectroscopy (DR-UV Vis), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy/energy-dispersive X-ray spectrometry (SEM-EDS) and High-resolution transmission electron microscopy (HR-TEM). Zeta potential analysis indicated an increase in hydrodynamic diameter with high colloidal stability (–23.3 to −28.5 mV). The percentage cumulative Cpt release was studied using automated Franz cell and dialysis membrane technique. The effect of Cpt release on 4 wt%Ag impregnated on different shaped supports was investigated using cubic SBA-16 (Santa Barbara Amorphous), MFI type Ti-ZSM-5 (Zeolite Socony Mobil #5), hexagonal mesosilicalite, nanotube halloysite, and Ag-silicalite, respectively. Drug release study indicates that Ag loading controls the Cpt release. The kinetics of drug release for the different formulations was examined using Korsmeyers-Peppas model. Release constant (k) and release exponent (n) were utilized for the rate of drug release and diffusion mechanisms, respectively. The in vitro study revealed an efficient interaction of nanoformulations promoting both antibacterial and anticancer activities.

Pr3+ Ion-Substituted Ni-Co Nano-Spinel Ferrites: Their Synthesis, Characterization, and Biocompatibility for Colorectal Cancer and Candidaemia.

Nanotherapeutics have attracted tremendous research interest in the modern pharmaceutical and biomedical industries due to their potential for drug development, targeted delivery, and therapeutic applications. Therefore, the current study underpins the synthesis of praseodymium ion (Pr3+)-substituted Ni0.5Co0.5Fe2O4 nano-spinel ferrites, (Co0.5Ni0.5PrxFe2-xO4 (0.0 ≤ x ≤ 0.10) NSFs, CoNiPr (x ≤ 0.10) NSFs) via the sonochemical route for its application as a nanotherapeutic treatment option. The synthesized nanomaterial was characterized using various analytical techniques, including scanning/transmission electron microscopy (SEM) and X-ray powder diffractometry (XRD). After substitution with Pr (x = 0.08), the particle size, polydispersity index, and zeta potential analysis indicated an increase in hydrodynamic diameter, with an average zeta potential value of -10.2 mV. The investigation of CoNiPr (x ≤ 0.10) NSFs on colorectal cancer (HCT-116) cells demonstrated a significant effect on cancer cell viability. The inhibitory concentration (IC50) of CoNiPr (x ≤ 0.10) NSFs was between 46 ± 0.91 and 288 ± 8.21 for HCT-116 cells. The effect of CoNiPr (x ≤ 0.10) NSFs on normal human embryonic kidney (HEK-293) cells showed a reduction in the HEK-293 cell viability; however, the cell viability was better than HCT-116. The NSFs treatment also showed morphological changes in cancer cell nuclei, as revealed by DAPI (4',6-diamidino-2-phenylindole), nuclear disintegration, and chromatic fragmentation, which are signs of apoptosis or programmed cell death. To examine the potential antifungal effects of CoNiPr NSFs on Candida albicans, known to cause candidemia among cancer patients, the viability of the cells was assessed post treatment with CoNiPr (x ≤ 0.10) NSFs. The increasing ratio of dopant had a moderate impact on the percentage of cell viability loss of 42, 44, and 43% with x = 0.06, 0.08, and 0.10, respectively. These results reinforce that increased dopant significantly impacts the antifungal properties of the synthesized nanomaterial. These findings support the idea that NSFs might be useful in pharmaceuticals.

Lyophilized Lipid Liquid Crystalline Nanoparticles as an Antimicrobial Delivery System.

Lipid liquid crystalline nanoparticles (LCNPs) are unique nanocarriers that efficiently deliver antimicrobials through biological barriers. Yet, their wide application as an antimicrobial delivery system is hindered by their poor stability in aqueous dispersions. The production of dried LCNP powder via lyophilization is a promising approach to promote the stability of LCNPs. However, the impact of the process on the functionality of the loaded hydrophobic cargoes has not been reported yet. Herein, we investigated the potential of lyophilization to produce dispersible dry LCNPs loaded with a hydrophobic antimicrobial compound, gallium protoporphyrin (GaPP). The effect of lyophilization on the physicochemical characteristics and the antimicrobial activity of rehydrated GaPP-LCNPs was studied. The rehydrated GaPP-LCNPs retained the liquid crystalline structure and were monodisperse (PDI: 0.27 ± 0.02), with no significant change in nanoparticle concentration despite the minor increase in hydrodynamic diameter (193 ± 6.5 compared to 173 ± 4.2 prior to freeze-drying). Most importantly, the efficacy of the loaded GaPP as an antimicrobial agent and a photosensitizer was not affected as similar MIC values were obtained against S. aureus (0.125 µg/mL), with a singlet oxygen quantum yield of 0.72. These findings indicate the suitability of lyophilization to produce a dry form of LCNPs and pave the way for future studies to promote the application of LCNPs as an antimicrobial delivery system.

Expression, Purification, and Biological Evaluation of XTEN-GCSF in a Neutropenic Rat Model.

Granulocyte colony-stimulating factor (GCSF) stimulates the proliferation of neutrophils but it has low serum half-life. Therefore, the present study was done to investigate the effect of XTENylation on biological activity, pharmacokinetics, and pharmacodynamics of GCSF in a neutropenic rat model. XTEN tag was genetically fused to the N-terminal region of GCSF-encoding gene fragment and subcloned into pET28a expression vector. The cytoplasmic expressed recombinant protein was characterized through intrinsic fluorescence spectroscopy (IFS), dynamic light scattering (DLS), and size exclusion chromatography (SEC). In vitro biological activity of the XTEN-GCSF protein was evaluated on NFS60 cell line. Hematopoietic properties and pharmacokinetics were also investigated in a neutropenic rat model. An approximately 140kDa recombinant protein was detected on SDS-PAGE. Dynamic light scattering and size exclusion chromatography confirmed the increase in hydrodynamic diameter of GCSF molecule after XTENylation. GCSF derivatives showed efficacy in proliferation of NFS60 cell line among which the XTEN-GCSF represented the lowest EC50 value (100.6pg/ml). Pharmacokinetic studies on neutropenic rats revealed that XTEN polymer could significantly increase protein serum half-life in comparison with the commercially available GCSF molecules. PEGylated and XTENylated GCSF proteins were more effective in stimulation of neutrophils compared to the GCSF molecule alone. XTENylation of GCSF represented promising results in in vitro and in vivo studies. This approach can be a potential alternative to PEGylation strategies for increasing serum half-life of protein.

Interaction of Colloidal Gold Nanoparticles with Urine and Saliva Biofluids: An Exploratory Study.

The use of gold nanoparticles for drug delivery, photothermal or photodynamic therapy, and biosensing enhances the demand for knowledge about the protein corona formed on the surface of nanoparticles. In this study, gold nanospheres (AuNSs), gold nanorods (AuNRs), and gold nanoflowers (AuNFs) were incubated with saliva or urine. After the interaction, the surface of gold nanoparticles was investigated using UV-VIS spectroscopy, zeta potential, and dynamic light scattering. The shifting of the localized surface plasmon resonance (LSPR) band, the increase in hydrodynamic diameter, and the changes in the surface charge of nanoparticles indicated the presence of biomolecules on the surface of AuNSs, AuNRs, and AuNFs. The incubation of AuNFs with saliva led to nanoparticle aggregation and minimal protein adsorption. AuNSs and AuNRs incubated in saliva were analyzed through liquid chromatography with tandem mass spectrometry (LC-MS/MS) to identify the 96 proteins adsorbed on the surface of the gold nanoparticles. Among the 20 most abundant proteins identified, 14 proteins were common in both AuNSs and AuNRs. We hypothesize that the adsorption of these proteins was due to their high sulfur content, allowing for their interaction with gold nanoparticles via the Au-S bond. The presence of distinct proteins on the surface of AuNSs or AuNRs was also investigated and possibly related to the competition between proteins present on the external layers of corona and gold nanoparticle morphology.

Influence of ultrasound on the mechanism of conjugation between epigallocatechin gallate and β‐lactoglobulin for function improvement

SummaryEpigallocatechin‐3‐gallate (EGCG) can improve functional properties of β‐Lactoglobulin (βLg) by conjugation. The effects of ultrasound, a useful tool in improving the conjugation efficiency, on the various functional properties of βLg‐EGCG conjugates were investigated in this study. Results revealed βLg‐EGCG conjugates transformed from cross‐linked state to fragments of various forms with ultrasound treatment with increased of binding affinity. Meanwhile, ultrasound increased secondary structural changes in βLg in the conjugated state. Functionally, ultrasound decreased the immunoglobulin E (IgE) combing capacity of βLg and enhanced its antioxidant properties by promoting the interaction between EGCG and βLg. Moreover, ultrasound induced an increase in hydrodynamic diameter and lowered the absolute zeta potential of βLg‐EGCG conjugates, resulting in an increase in digestibility, as well as foaming and emulsification abilities, while, a decrease in thermal stability. The results provide valuable information for obtaining βLg with better functional properties for industrial production by ultrasound‐assisted covalent binding of EGCG with βLg.

Scalable manufacturing platform for the production of PEGylated heme albumin.

Cell-free heme, which was previously shown to have adverse effects on the innate immune system, does not induce inflammation when bound to a protein carrier via overexpression of the enzyme heme-oxygenase 1 (HO-1). Studies in mouse macrophage cell culture and human endothelial cells have confirmed HO-1 catalyzed breakdown of protein bound heme into biliverdin, iron, and carbon monoxide (CO), which elicits anti-inflammatory effects. However, to fully realize the anti-inflammatory therapeutic effects of heme, a colloidally stable heme protein carrier must be developed. To accomplish this goal, we incorporated multiple heme molecules into human serum albumin (HSA) via partial unfolding of HSA at basic pH followed by refolding at neutral pH, and subsequently conjugated the surface of the heme-HSA complex with polyethylene glycol (PEG) to stabilize heme-HSA. Quantification studies confirmed that a maximum of 5-6 hemes could be bound to HSA without precipitation or degradation of heme-HSA. Dynamic light scattering, size exclusion-high performance liquid chromatography (SEC-HPLC), and matrix-assisted laser desorption/ionization time-of-flight(MALDI-TOF) mass spectrometry confirmed the increase in hydrodynamic diameter and molecular weight (MW), respectively, upon PEGylation of heme-HSA. Furthermore, PEG-heme-HSA was stable upon exposure to different pH environments, freeze-thaw cycles, and storage at 4°C. Taken together, we devised a synthesis and purification platform for the production of PEGylated heme-incorporated HSA that can be used to test the potential anti-inflammatory effects of heme in vivo.

X-Ray Photon Correlation Spectroscopy Towards Measuring Nanoparticle Diameters in Biological Environments Allowing for the In Situ Analysis of their Bio-Nano Interface.

X-ray photon correlation spectroscopy (XPCS), a synchrotron source-based technique to measure sample dynamics, is used to determine hydrodynamic diameters of gold nanoparticles (Au NPs) of different sizes in biological environments. In situ determined hydrodynamic diameters are benchmarked with values obtained by dynamic light scattering. The technique is then applied to analyze the behavior of the Au NPs in a biological environment. First, a concentration-dependent agglomeration in the presence of NaCl is determined. Second, concentration-dependent increase in hydrodynamic diameter of the Au NPs upon the presence of proteins is determined. As X-rays in the used energy range are barely scattered by biological matter, dynamics of the Au NPs can be also detected in situ in complex biological environments, such as blood. These measurements demonstrate the possibility of XPCS for insitu analytics of nanoparticles (NPs) in biological environments where similar detection techniques based on visible light would severely suffer from scattering, absorption, and reflection effects.

Production and stability of food-grade liposomes containing microbial carotenoids from Rhodotorula mucilaginosa

We demonstrated the technical feasibility of obtaining carotenoids-loaded liposomes from soybean lecithins using an ethanol injection technique. We evaluated the influence of three lecithin-types with different phosphatidylcholine content and microbial carotenoids produced by yeast Rhodotorula mucilaginosa on liposome properties. The liposomal systems were characterized by average hydrodynamic diameter, polydispersity index, ζ-potential, and stability under different pH and heat temperature conditions commonly observed in food processing. The lecithin type and concentration used to produce liposomes significantly influence the hydrodynamic diameter, polydispersity index, and ζ-potential. In general, we observed the presence of liposomes with diameters ranging from 150 to 221 nm and a polydispersity index of approximately 0.300 when Lipoid S45 was used. The incorporation of microbial carotenoids promoted a significant increase in hydrodynamic diameter and ζ-potential, while carotenoid-loaded liposomes showed a lower polydispersity index. The carotenoid-loaded liposomes submitted to pH 3 presented a visual phase separation, while liposomes submitted at 70 °C for 15 min showed degradation of carotenoids equal to control assay (without treatment). We concluded that it is possible to incorporate microbial carotenoids in food-grade liposomal systems, allowing for further studies aimed at their application as an encapsulating and/or delivery system to be used in aqueous food products.

A robust post-insertion method for the preparation of targeted siRNA LNPs

Targeted delivery of nucleic acids is gaining momentum due to improved efficacy, selectivity, increased circulation time and enhanced tissue retention in target cells. Using nucleic acid-based therapies previously undruggable targets have proven now to be amenable for treatment. Currently, several methods for preparing targeted or labelled delivery vehicles for nucleic acids are based on liposomal formulations. Lipid nanoparticles (LNPs) are structurally different from liposomes and these methods should therefore be evaluated before being translated to siRNA LNPs preparation protocols. Here, we describe a robust and facile method for the preparation of targeted or fluorescently labelled siRNA LNPs. Using a copper free strain-promoted azide-alkyne cycloaddition (SPAAC) we demonstrate that post-insertion of ligand-lipid conjugates into preformed LNPs is superior to direct-surface modification because it preserves the physicochemical parameters of the LNPs. We found that the time point of solvent removal by dialysis is critical and affects the hydrodynamic diameter of the LNPs; post-insertion after dialysis shows the smallest increase in hydrodynamic diameter and polydispersity index (PDI). The post-insertion of ligand-lipid conjugates also proceeded with rapid kinetics and high efficacy over a wide temperature range. Using this optimised protocol, we generated siRNA LNPs containing both targeting and fluorescent tracking ligands allowing us to monitor siRNA LNP uptake kinetics in dependence of the targeting ligand. In aggregate, we describe a robust approach for the generation of targeted and labelled siRNA LNPs that allows their controlled and facile decoration with ligand combinations.

Structural and Functional Characterization of Covalently Modified Proteins Formed By a Glycating Agent, Glyoxal.

Glycation, the main consequence of hyperglycemia, is one of the major perpetrators of diabetes and several other conditions, including coronary and neurodegenerative complications. Such a hyperglycemic condition is represented by a large increase in levels of various glycation end products including glyoxal, methylglyoxal, and carboxymethyl-lysine among others. These glycation end products are known to play a crucial role in diabetic complications due to their ability to covalently modify important proteins and enzymes, specifically at lysine residues (a process termed as glycation), making them non-functional. Previous studies have largely paid attention on characterization and identification of these reactive glycating agents. Structural and functional consequences of proteins affected by glycation have not yet been critically investigated. We have made a systematic investigation on the early conformational changes and functional alterations brought about by a glycating agent, glyoxal, on different proteins. We found that the early event in glycation includes an increase in hydrodynamic diameter, followed by minor structural alterations sufficient to impair enzyme activity. The study indicates the importance of glyoxal-induced early structural alteration of proteins toward the pathophysiology of hyperglycemia/diabetes and associated conditions.

Poly acrylic acid stabilized magnetic nanoemulsions for visual defect detection: Effect of pH on detection sensitivity and colloidal stability

Magnetic field assisted tunable colour contrast in magnetic nanoemulsions is exploited for visual detection of defects in ferromagnetic components. We demonstrate an enhanced defect detection sensitivity by stabilizing oil-in-water magnetic nanoemulsion with poly acrylic acid (PAA) at varying pH. In this detection technique, the variation of magnetic permeability, in the vicinity of the defects, causes magnetic flux leakage, which results in a distinct colour contrast on the magnetic nanoemulsion sensor due to the formation of anisotropic periodic structures, parallel to the external field direction, where the inter-droplet spacing within the linear chains depends on the effective magnetic flux. By exploiting this colour and magnetic flux dependence, severity of the defects is assessed by observing the colour contrast. Our studies indicate that defect detection sensitivity decreases with increasing pH due to globule-to-coil conformational transition of the interfacial PAA molecules. With increasing pH, the PAA network swells due to mobile counter-ions induced osmotic pressure and electrostatic repulsion between the charged monomer units, leading to a solvated coil-like configuration, which is confirmed from the increase in hydrodynamic diameter and zeta potential. The inter-droplet force measurements show an increase in decay length by ~3.5 times, when pH is increased from ~1.5 to ~4.0. The lower decay length at pH ~ 1.5 indicates the formation of linear chain-like structures with smaller inter-droplet spacing near the defect edges, where the magnetic flux leakage is maximum. This results in a fewer number of randomly oriented droplets at the defect centre, thereby enhancing the defect detection sensitivity at lower pH. However, nanoemulsions stabilized at pH > 3 show increased colloidal stability, as compared to pH ~ 1.5. Our studies indicate that nanoemulsions at pH ~ 3.5 exhibit an optimum colloidal stability with good defect detection sensitivity. The obtained results are beneficial for developing high sensitivity, reliable and reusable magnetic nanoemulsion sensors for naked eye visualization of defects in ferromagnetic components.

Protein-stabilized silver nanoparticles encapsulating gentamycin for the therapy of bacterial biofilm infections.

Aim: An antibiotic-conjugated protein-stabilized nanoparticle hybrid system was developed to combat the challenges faced during the treatment of drug-resistant bacterial biofilm-associated infections. Materials & methods: Biocompatible silver nanoparticles were synthesized using intracellular protein and gentamycin was attached. The resulting nanohybrid was characterized and its antibacterial efficiency was assessed against Gram-positive, Gram-negative and drug-resistant bacteria. Results: Spectroscopic and electron microscopic analysis revealed that the nanoparticles were spherical with a diameter of 2-6nm. Red-shifting of the surface plasmon peak and an increase in hydrodynamic diameter confirmed attachment of gentamycin. The nanohybrid exhibited antibacterial efficiency against a range of bacteria with the ability to inhibit and disrupt bacterial biofilm. Conclusion: A unique nanohybrid was designed that has potential to be used to control drug-resistant bacterial infections in the future.

Scale-up of microreactor: Effects of hydrodynamic diameter on liquid–liquid flow and mass transfer

To examine the scalability of a microreactor to the milli-scale, the liquid–liquid two-phase flow and mass transfer in a capillary reactor system were investigated. The flow pattern gradually transformed from a surface-force-controlled flow into a gravity-force-controlled flow with an increase of hydrodynamic diameter. In the T-mixer, the volumetric mass-transfer coefficient decreased and increased with an increase in the capillary diameter at low and high superficial liquid velocities, respectively. Because of the different mass-transfer mechanisms in the T-mixer and capillary, this scale-up effect became weaker in the capillary reactor system, particularly at a high superficial liquid velocity. A minimum 18% of mass was transferred in the T-mixer even at the milli-scale, suggesting the significant contribution of the T-mixer to mass transfer in the capillary reactor system. Empirical equations for predicting the volumetric mass-transfer coefficient of the T-mixer and the capillary reactor system in the hydrodynamic diameter range of 0.8–3.0 mm were formulated.

MRI Relaxivity Changes of the Magnetic Nanoparticles Induced by Different Amino Acid Coatings.

In this study, we analysed the physico-chemical properties of positively charged magnetic fluids consisting of magnetic nanoparticles (MNPs) functionalised by different amino acids (AAs): glycine (Gly), lysine (Lys) and tryptophan (Trp), and the influence of AA–MNP complexes on the MRI relaxivity. We found that the AA coating affects the size of dispersed particles and isoelectric point, as well as the zeta potential of AA–MNPs differently, depending on the AA selected. Moreover, we showed that a change in hydrodynamic diameter results in a change to the relaxivity of AA–MNP complexes. On the one hand, we observed a decrease in the relaxivity values, r1 and r2, with an increase in hydrodynamic diameter (the relaxivity of r1 and r2 were comparable with commercially available contrast agents); on the other hand, we observed an increase in r2* value with an increase in hydrodynamic size. These findings provide an interesting preliminary look at the impact of AA coating on the relaxivity properties of AA–MNP complexes, with a specific application in molecular contrast imaging originating from magnetic nanoparticles and magnetic resonance techniques.

Layer-by-layer pH-sensitive nanoparticles for drug delivery and controlled release with improved therapeutic efficacy in vivo

In this work, a pH-sensitive liposome–polymer nanoparticle (NP) composed of lipid, hyaluronic acid (HA) and poly(β-amino ester) (PBAE) was prepared using layer-by-layer (LbL) method for doxorubicin (DOX) targeted delivery and controlled release to enhance the cancer treatment efficacy. The NP with pH-sensitivity and targeting effect was successfully prepared by validation of charge reversal and increase of hydrodynamic diameter after each deposition of functional layer. We further showed the DOX-loaded NP had higher drug loading capacity, suitable particle size, spherical morphology, good uniformity, and high serum stability for drug delivery. We confirmed that the drug release profile was triggered by low pH with sustained release manner in vitro. Confocal microscopy research demonstrated that the NP was able to effectively target and deliver DOX into human non-small cell lung carcinoma (A549) cells in comparison to free DOX. Moreover, the blank NP showed negligible cytotoxicity, and the DOX-loaded NP could efficiently induce the apoptosis of A549 cells as well as free DOX. Notably, in vivo experiment results showed that the DOX-loaded NPs effectively inhibited the growth of tumor, enhanced the survival of tumor-bearing mice and improved the therapeutic efficacy with reduced side-effect comparing with free drug. Therefore, the NP could be a potential intelligent anticancer drug delivery carrier for cancer chemotherapy, and the LbL method might be a useful strategy to prepare multi-functional platform for drug delivery.

Quantitative atomic force microscopy provides new insight into matrix vesicle mineralization

Matrix vesicles (MVs) are a class of extracellular vesicles that initiate mineralization in cartilage, bone, and other vertebrate tissues by accumulating calcium ions (Ca2+) and inorganic phosphate (Pi) within their lumen and forming a nucleation core (NC). After further sequestration of Ca2+ and Pi, the NC transforms into crystalline complexes. Direct evidence of the existence of the NC and its maturation have been provided solely by analyses of dried samples. We isolated MVs from chicken embryo cartilage and used atomic force microscopy peak force quantitative nanomechanical property mapping (AFM-PFQNM) to measure the nanomechanical and morphological properties of individual MVs under both mineralizing (+Ca2+) and non-mineralizing (–Ca2+) fluid conditions. The elastic modulus of MVs significantly increased by 4-fold after incubation in mineralization buffer. From AFM mapping data, we inferred the morphological changes of MVs as mineralization progresses: prior to mineralization, a punctate feature, the NC, is present within MVs and this feature grows and stiffens during mineralization until it occupies most of the MV lumen. Dynamic light scattering showed a significant increase in hydrodynamic diameter and no change in the zeta potential of hydrated MVs after incubation with Ca2+. This validates that crystalline complexes, which are strongly negative relative to MVs, were forming within the lumen of MVs. These data were substantiated by transmission electron microscopy energy dispersive X-ray and Fourier transform infrared spectroscopic analyses of dried MVs, which provide evidence that the complexes increased in size, crystallinity, and Ca/P ratio within MVs during the mineralization process.