3D additive manufactured composite scaffolds with antibiotic-loaded lamellar fillers for bone infection prevention and tissue regeneration

Bone infections following open bone fracture or implant surgery remain a challenge in the orthopedics field.In order to avoid high doses of systemic drug administration,optimized local antibiotic release from scaffolds is required.3D additive manufactured(AM)scaffolds made with biodegradable polymers are ideal to support bone healing in non-union scenarios and can be given antimicrobial properties by the incorporation of antibiotics.In this study,ciprofloxacin and gentamicin intercalated in the interlamellar spaces of magnesium aluminum layered double hydroxides(MgAl)andα-zirconium phosphates(ZrP),respectively,are dispersed within a thermoplastic polymer by melt compounding and subsequently processed via high temperature melt extrusion AM(~190◦C)into 3D scaffolds.The inorganic fillers enable a sustained antibiotics release through the polymer matrix,controlled by antibiotics counterions exchange or pH conditions.Importantly,both antibiotics retain their functionality after the manufacturing process at high temperatures,as verified by their activity against both Gram+and Gram-bacterial strains.Moreover,scaffolds loaded with filler-antibiotic do not impair human mesenchymal stromal cells osteogenic differentiation,allowing matrix mineralization and the expression of relevant osteogenic markers.Overall,these results suggest the possibility of fabricating dual functionality 3D scaffolds via high temperature melt extrusion for bone regeneration and infection prevention.

Astrocytes and retrograde degeneration of nigrostriatal dopaminergic neurons in Parkinson’s disease:removing axonal debris

Objective:The dopaminergic nigrostriatal neurons(DA cells)in healthy people present a slow degeneration with aging,which produces cellular debris throughout life.About 2%-5%of people present rapid cell degeneration of more than 50%of DA cells,which produces Parkinson's disease(PD).Neuroinflammation accelerates the cell degeneration and may be critical for the transition between the slow physiological and the rapid pathological degeneration of DA cells,particularly when it activates microglial cells of the medial forebrain bundle near dopaminergic axons.As synaptic debris produced by DA cell degeneration may trigger the parkinsonian neuroinflammation,this study investigated the removal of axonal debris produced by retrograde degeneration of DA cells,paying particular attention to the relative roles of astrocytes and microglia.Methods:Rats and mice were injected in the lateral ventricles with 6-hydroxydopamine,inducing a degeneration of dopaminergic synapses in the striatum which was not accompanied by non-selective tissue damage,microgliosis or neuroinflammation.The possible retrograde degeneration of dopaminergic axons,and the production and metabolization of DA-cell debris were studied with immunohistochemical methods and analyzed in confocal and electron microscopy images.Results:The selective degeneration of dopaminergic synapses in the striatum was followed by a retrograde degeneration of dopaminergic axons whose debris was found within spheroids of the medial forebrain bundle.These spheroids retained mitochondria and most(e.g.,tyrosine hydroxylase,the dopamine transporter protein,and amyloid precursor protein)but not all(e.g.,α-synuclein)proteins of the degenerating dopaminergic axons.Spheroids showed initial(autophagosomes)but not late(lysosomes)components of autophagy(incomplete autophagy).These spheroids were penetrated by astrocytic processes of the medial forebrain bundle,which provided the lysosomes needed to continue the degradation of dopaminergic debris.Finally,dopaminergic proteins were observed in the cell somata of astrocytes.No microgliosis or microglial phagocytosis of debris was observed in the medial forebrain bundle during the retrograde degeneration of dopaminergic axons.Conclusions:The present data suggest a physiological role of astrocytic phagocytosis of axonal debris for the medial forebrain bundle astrocytes,which may prevent the activation of microglia and the spread of retrograde axonal degeneration in PD.