From biomass to nanomaterials: a green Layer-by-Layer strategy for developing multifunctional silica mesoporous-based nanoparticles with improved antioxidant properties for regenerative medicine

Posttraumatic stress disorder (PTSD) is a chronic debilitating dysfunction that may occur due to acute stress in the early aftermath of trauma. Not everyone who experiences a traumatic event will go on to develop acute or chronic dysfunction, lifetime prevalence of PTSD is estimated at around 3.9% worldwide. This syndrome is characterized by four symptom clusters, such as, intrusive thoughts, avoidance of reminders, feeling and thinking negatively, as well as arousal and reactive symptoms. Further biomarker studies found out how these psycho-behavioral abnormalities in immune indicators are jointly among patients. Results have shown higher levels of proinflammatory cytokines, namely, interleukin IL-1β, IL-6, tumour necrosis factor TNF-α, interferon gamma (IFN-ɣ), emphasising how inflammation is one potential dysregulated mechanism in PTSD. In particular, the most common underlying mechanisms implicated in PTSD-related inflammatory dysregulation are altered autonomic nervous system (ANS) activity and an impaired reaction of the hypothalamic–pituitary–adrenal (HPA) axis to perceived stress, resulting in a chronic low-grade pro-inflammatory state. In this context, this work aimed at engineering a natural polymer based nanocarrier system for the delivery of antioxidant extracts as an innovative approach to effectively target and reduce inflammation. To this purpose, layer by layer (LbL) deposition was adopted to build an antioxidant polyelectrolyte multilayer on the surface of spherical silica mesoporous nanoparticles (MNPs) of 200 nm. Pectin (PE) and chitosan (CH) are natural polymer with intrinsic biocompatibility and non-toxicity proprieties. Exploiting their opposite zeta potential, measured using dynamic light scattering (DLS), PE (-39 mV) and CH (+40 mV) were used as polyanion and polycation respectively in the alternated deposition. Due to their negative charge (-28 mV) MNPs were first immersed in CH solution followed by PE solution for a total of 5 layers. To impart the MNPs LbL coating with anti-inflammatory properties for targeting PTSD inflammation, green antioxidants were extracted from cocoa and coffee biowaste and added to the pectin solution. Antioxidants extraction parameters, namely, temperature (˚C), time (min) and liquid/solid ratio (mL/mg) were optimized through design of experiments (DOEs) and optimized ultrasound assisted extraction was performed both for cocoa and coffee biowaste using a 50% ethanol solution. Different active compounds were detected in the extracts through HPLC-mass spectroscopy, total phenolic content (TPC) was valuated using Folin-Ciocalteu reagent and antioxidant performance was evaluated with FRAP colorimetric methods. The highest TPC and antioxidant activity was performed by cocoa extract (3.7 GAE mg/mL and 996.7 µmol Fe/100g). The morphological and chemical characterization of synthesized MNPs, were carried out performing TEM and FTIR analysis which confirmed all polyelectrolyte presence. Moreover, the antibacterial activity of the green synthesized MNPs against bacterial strains of Klebsiella pneumoniae, Staphylococcus aureus and Streptococcus pyogenes was tested in terms of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) using Klebsiella pneumoniae, Staphylococcus aureus and Streptococcus pyogenes. MNPs systems cytocompatibility was tested trough Live&Dead and Alamar Blue assays, while MNPs antioxidant activity was tested on neuronal cells performing ROS test.