Biosensors detect specific bio-analytes by generating a measurable signal from the interaction between the sensing element and the target molecule. Surface acoustic wave (SAW) biosensors offer unique advantages due to their high sensitivity, real-time response capability, and label-free detection. The typical SAW modes are the Rayleigh mode and the shear-horizontal mode. Both present pros and cons for biosensing applications and generally need different substrates and device geometries to be efficiently generated. This study investigates and characterizes ultra-high-frequency (UHF-) SAW resonator biosensors. It reveals the simultaneous presence of the two typical SAW modes, clearly separated in frequency, called slow and fast. The two modes are studied by numerical simulations and biosensing experiments with the glial-fibrillary-acidic-protein (GFAP) biomarker. The slow mode is generally more sensitive to changes in surface properties, such as temperature and mass changes, by a factor of about 1.4 with respect to the fast mode.

Glial fibrillary acidic protein (GFAP) is the major intermediate filament III protein of astroglia cells which is upregulated in traumatic brain injury (TBI). Here we reported that GFAP is truncated at both the C- and N-terminals by cytosolic protease calpain to GFAP breakdown products (GBDP) of 46-40K then 38K following pro-necrotic (A23187) and pro-apoptotic (staurosporine) challenges to primary cultured astroglia or neuron-glia mixed cells. In addition, with another pro-apoptotic challenge (EDTA) where caspases are activated but not calpain, GFAP was fragmented internally, generating a C-terminal GBDP of 20 kDa. Following controlled cortical impact in mice, GBDP of 46-40K and 38K were formed from day 3 to 28 post-injury. Purified GFAP protein treated with calpain-1 and -2 generates (i) major N-terminal cleavage sites between A-56 and A-75, and (ii) major C-terminal cleavage sites between T-383 and Q-388, producing a limit fragment of 38K. Caspase-6 treated GFAP was cleaved at D-78, R-79, D-266 and A-267, where GFAP was relatively resistant to caspase-3. We also derived a GBDP-38K N-terminal-specific antibody which only labels injured astroglia cell body in both cultured astroglia and mouse cortex and hippocampus after TBI. As a clinical translation, we observed that CSF samples collected from severe human TBI have elevated levels of GBDP-38K as well as two C-terminally released GFAP peptides (DGEVIKES and DGEVIKE). Thus, in addition to intact GFAP, both the GBDP-38K as well as unique GFAP released C-terminal proteolytic peptides species might have the potential in tracking brain injury progression.

Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) are two structurally-related immunosuppressive peptides. However, the underlying mechanisms through which these peptides regulate microglial activity are not fully understood. Using lipopolysaccharide (LPS) to induce an inflammatory challenge, we tested whether PACAP or VIP differentially affected microglial activation, morphology and cell migration. We found that both peptides attenuated LPS-induced expression of the microglial activation markers Iba1 and iNOS (###p<0.001), as well as the pro-inflammatory mediators IL-1β, IL-6, Itgam and CD68 (###p<0.001). In contrast, treatment with PACAP or VIP exerted distinct effects on microglial morphology and migration. PACAP reversed LPS-induced soma enlargement and increased the percentage of small-sized, rounded cells (54.09% vs 12.05% in LPS-treated cells), whereas VIP promoted a phenotypic shift towards cell subpopulations with mid-sized, spindle-shaped soma (48.41% vs 31.36% in LPS-treated). Additionally, PACAP was more efficient than VIP in restoring LPS-induced impairment of cell migration and the expression of urokinase plasminogen activator (uPA) in BV2 cells compared with VIP. These results suggest that whilst both PACAP and VIP exert similar immunosuppressive effects in activated BV2 microglia, each peptide triggers distinctive shifts towards phenotypes of differing morphologies and with differing migration capacities.

Background & Objective. Perinatal hypoxia acutely triggers the release of cytokines and chemokines from neurons, astrocytes and microglia. In response to hypoxia-ischemia resting/ramified microglia proliferate and undergo activation, with the production of proinflammatory molecules. The brain damage extension seems to be related with both the severity of hypoxia and the balance between pro and anti-inflammatory host response. Methods: In this preliminary study we compared in 10 neonates with hypoxic ischemic encephalopathy (HIE), during therapeutic hypothermia (TH), plasmatic cytokines and other inflammatory molecules levels: monocytic chemotactic-protein-1 (CCL2/MCP-1), CXCL8, glial fibrillary acidic protein (GFAP), Interferon gamma (IFN y), Interleukin 10 (IL-10), IL-18, IL-6, CCL3, ENOLASE2, Colony Stimulating Factor(GM-CSF), IL-1b, IL-12p70, IL-33, Tumor Necrosis Factor alpha(TNF), collected at four different time points during TH (24 hours, 25-48 hours, 49-72 hours) , and after the rewarming (7-10 days from birth). Five of enrolled babies had pathological brain MRI (“cases”) and 5 had a normal examination (“controls”). Cytokines were measured by Magnetic Luminex Assay (Luminex SV 013-17 (14), instrument Biorad Bio-Plex 100 s.n. LX 10005039304). MRI images were classified according to the Barkovich score. Results: Mean levels of all cytokines and molecules at time T1 were not significantly different in the two groups of patients. Comparing samples paired by day of collection, the greatest differences between cases and controls were found at times T2 and T3, during TH. After rewarming, some molecules showed an upward trend. At T4, levels tended to be close again (with the exception of IL-6, IL10 and IL18). Infants with worse MRI showed plasmatic GFAP levels higher than those with normal MRI, while their IL-18 was lower. Mean levels of CCL3MIP1alpha, GMCSF, IL1BETA overlapped throughout the observation period in both the groups of neonates. Conclusion. In children with worse brain MRI we found high levels of GFAP and of IL-10 at T4, considered respectively an early biomarker of brain damage and a predictor of adverse outcome, according to the literature, and a trend towards low IL-18 levels. We found the greatest, although not significant, difference between molecules levels in cases and controls at time points T2 and T3, during TH. With the rewarming some molecules showed an upward trend. We cannot exclude that the small sample size may prevent significance in the differences from being achieved.

Optic neuritis (ON) is the most common cause of vision loss in young adults. It manifests as acute or subacute vision loss, often accompanied by retrobulbar discomfort or pain on eye movements. Typical ON is associated with Multiple Sclerosis and is generally mild and steroid-responsive, whereas atypical forms are characterized by unusual features, such as optic disc edema, poor treatment response and bilateral involvement, and are often associated with autoantibodies against aquaporin-4 (AQP4) and Myelin Oligodendrocyte Glycoprotein (MOG). However, in rare cases AQP4 and MOG antibodies will come back negative, plunging the clinician in a diagnostic conundrum. Seronegative ON warrants a broad differential diagnosis, including autoantibody-associated, granulomatous, and systemic disorders. These rare forms need to be identified promptly, as their management and prognosis is greatly different. The scope of this review is to describe possible, rarer etiologies of ON when AQP4 and MOG antibodies are negative and discuss their diagnosis and treatment.