# Floor modification of gold nanoparticles with neuron-targeted exosome for enhanced blood–mind barrier penetration

### Technology of cells transiently expressing Lamp2b fusion protein

Sub-confluent monolayer cultures of reworked human embryonic kidneys (HEK293T) have been cultured in serum free Dulbecco’s modified Eagle’s medium (DMEM) and transfected with pcDNA GNSTM-Three-RVG-10-Lamp2b-HA vector for expression of Lamp2b fusion proteins in mammalian cells by lipofectamine (Invitrogen). Exosomes have been harvested from the supernatant of transfected cells as beforehand described utilizing serial centrifugation13. Brieftly, the supernatant was spun at 300 × g for 10 min, 2,000 × g for 10 min, and 12,000 × g for 30 min to take away cells, cell particles, and apoptotic our bodies. Then, the supernatant have been spun 120,000 × g for 120 min utilizing ultracentrifuge (Beckman Coulter) to pellete exosomes. Exosome pellets have been washed in PBS and pelleted once more by way of ultracentrifugation earlier than performing experiment. Exosomes additionally produced from non-tranfected cells have been additionally ready and used as management exosomes. Western blotting was carried out for the evaluation of Lamp2b fusion protein expression utilizing the mouse monoclonal Anti-HA antibody (#H3663, Sigma). Main antibody was detected with horseradish peroxidase-conjugated anti-mouse (# 62–6520, Invitrogen) immunoglobulin G secondary antibody.

### Exosome/AuNPs particles fabrication and characterization

Gold nanoparticles (AuNPs) have been synthesized following Brown et al., 201021. Briefly, NaAuCl4·2H2O (zero.14 mmol) was dissolved in distilled water, after which the answer heated to 100 °C with steady stirring. Throughout boiling, sodium citrate (1% m/v) was added and boiled for 15 min earlier than cooling to room temperature. UV-visible spectra (λmax) 519–523 nm was employed to point the profitable formation of nanoparticles.

The AuNP coated exosome particles have been fabricated by a serial extrusion methodology. Briefly, the harvested exosomes from serial centrifugation have been blended with 200 µL of AuNPs at Abs 1.zero. The combination ratio was estimated based mostly on imply rely price of particles (DLS) and UV-VIS spectra of AuNPs. Each exosome and AuNPs have been incubated collectively in 2 mL phosphate buffered saline (PBS) pH 7.four at four °C for 30 min earlier than extrusion. Consequently, the combination of particles was then extruded serially via 400 nm, 200 nm and 100 nm polycarbonate porous membranes utilizing a mini extruder. The particles have been handed via the extruder repeatedly 10 occasions in every porous membrane to make sure that the AuNPs have been totally coated with exosome22,23. The combination of particles was centrifuged at 8000 rpm for 20 min to purify the exosome/AuNPs from an extra of exosomes. The pellets have been resuspended in 1 mL PBS, and the imply particle dimension measured earlier than and after the exosome coating.

Nanoparticle dimension (nm), polydispersity and floor cost (zeta potential, mV) have been measured by dynamic gentle scattering (DLS) utilizing a Malvern XP. Furthermore, your complete encapsulation of the exosome was noticed by the Raman spectra of malachite inexperienced on AuNPs utilizing Raman spectroscopy (Sierra Sequence Spectrometers (633 nm), Snowy Vary Devices, Laramie, WY, USA). As well as, the construction of the exosome/AuNPs was examined utilizing a transmission electron microscope.

For fluorescence labeling, the nanoparticles have been labeled with 1,1′-dioctadecyl-Three,Three,Three′,Three′-tetramethylindocarbocyanine perchlo-rate (DiI) dye. Dil labeling of exosome on nanoparticles, 1 mg/ml resolution of Dil was added to PBS (1:750) and incubated for 30 min earlier than eradicating extra dye by centrifugation. Dil-labeled particles have been resuspended in PBS and centrifuged at eight,000 rpm for 20 min. This process was repeated for 3 times to scrub extra dye away for additional experiments.

### Nanoparticle binding effectivity

Immortalized bEnd.Three mouse mind endothelial cell line, C6 rat glioma cells, or Hela cervical most cancers cells have been cultured have been cultured in Dulbecco’s modified Eagle’s medium (DMEM) with 10% fetal bovine serum (FBS), Three mM L-glutamine and 1% penicillin–streptomycin. All cell thpes have been maintained in a cell tradition incubator at 37 °C and with 5% CO2. All cell strains have been seeded in a 6-well plate until 90% of confluency over the underside of wells previous to an experiment. The in vitro circulation adhesion assay employed a parallel plate circulation chamber (PPFC) outfitted with silicon rubber gaskets forming the circulation channel (GlycoTech, Gaithersburg, MD, USA). Modified or unmodified AuNPs in PBS buffer (pH 7.four) was then added and allowed to circulation via the chamber as described in beforehand reported research24,25. Briefly, a single straight circulation channel (125 µm peak) was positioned over cultured cells and vacuum-seal to the circulation deck with the intention to arrange the circulation chamber. The wall shear price (γw;WSR) within the system was calculated from the adjustment of volumetric circulation price (Q) in response to

$$gamma _(s^)=frac6Q$$

the place h is the peak of channel (125 µm) and w is the channel width (1000 µm). The assays have been performed with laminar circulation via the channel at WSRs of 100 s−1.

Nanoparticles have been suspended in circulation buffer (1percentBSA in PBS) at a set focus of 6.5 × 106 particles/mL, after which launched into the circulation channel from an inlet reservoir at 100 s−1 operated by way of a syringe pump (ProSence NE-1000, Oosterhout, Netherland). After 10 minutes, the system was washed by circulation buffer and nanoparticle adhesion noticed on an Olympus IX71 inverted microscope fitted with a digital digicam (Olympus DP71). Particle binding density (#/mm2) was evaluated by manually counting of the variety of sure particles on cells after 10 min of circulation. This quantity was divided by the world of the sphere of view (20x magnification, A = zero.125 mm2) as described in a earlier research24. The information was collected at a continuing place alongside the size of the chamber for all experiments. Every knowledge level represents a mean of binding density from at the least three unbiased experiments and consists of at the least 10 fields of view per experiment.

### Permeability of gold nanoparticles via blood mind barrier mannequin (BBB mannequin)

The experimental process for build up the in vitro BBB mannequin is as in response to Li et al., 201026. To start with, the underside aspect of the Transwell filters (zero.four m pore sizes, PET, 6 or 12 properly; Corning, USA) have been coated with collagen kind I (eight g/cm2 in zero.02 N acetic acid) for 1 hr at room temperature (RT) to assist cell attachment. Then, the filters have been washed with PBS, and Astrocyte cells have been seeded onto the again of the Transwell filters at a density of two.44 × 104 cells/cm2. After Three h incubation, bEnd.Three cells have been seeded onto the highest aspect of the filters at a density of 105 cells/cm2 and co-cultured with astrocyte cells for Three days in DMEM with 10% fetal bovine serum, Three mM glutamine, and 1% PS. The BBB fashions have been characterised by detection of the tight junction proteins earlier than performing experiments, and trans-epithelial electrical resistance (TEER) was measured earlier than and after remedies of nanoparticles.

Transwells have been gently washed with PBS earlier than including nanoparticles stained with Dil in DMEM medium into the higher wells. The medium of decrease wells have been collected at 30 min, 1 hr, Three hr, 6 hr, 12 hr and 24 hr time factors. The focus of permeated particles was decided by measurement of fluorescene depth (SpectraMax). Permeability was evaluated in % as in comparison with complete quantity of nanoparticle added and remained in higher chamber.

### Murine mannequin and in vivo assay

Strategies have been carried out in accordance with animal ethics tips. All experimental protocols have been authorized by the Animal Ethics Committee of Thammasat College [017/2560]. Fifteen C57BL/6wild kind mice at eight–10 weeks previous have been used as animal fashions on this experiment. Mice have been randomly assigned into three teams of 5 animals, and AuNPs/exosome have been injected by way of the tail vein at a identical dosage in 200 μL in PBS /mouse. 1 hour after injection, mice have been anaesthetized with isoflurane. Then, mice have been perfused with ice-cold PBS and four% paraformaldehyde (PFA) in PBS, respectively. Mouse brains have been harvested and snap-frozen in liquid nitrogen. Consequently, they have been noticed utilizing an in vivo imaging instrument (Bruker). Subsequently, the brains have been washed Three occasions for 15 minutes with PBS earlier than being soaked in a single day with 20% sucrose. The mind was embedded in O.C.T. embedding medium and snap-frozen earlier than cryostat sectioned (Leica CM1950).

### Statistical evaluation

Important variations between teams have been analyzed by one-way or two-way evaluation of variance (ANOVA) adopted by Turkey’s a number of comparability post-tests. The statistical variations between two experimental teams have been analyzed by Scholar’s unpaired t-test. p-values < zero.05 have been thought-about vital.

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