A facile strategy for tuning the density of surface-grafted biomolecules for melt extrusion-based additive manufacturing applications

Melt extrusion-based additive manufacturing(ME-AM)is a promising technique to fabricate porous scaffolds for tissue engi-neering applications.However,most synthetic semicrystalline polymers do not possess the intrinsic biological activity required to control cell fate.Grafting of biomolecules on polymeric surfaces of AM scaffolds enhances the bioactivity of a construct;however,there are limited strategies available to control the surface density.Here,we report a strategy to tune the surface density of bioactive groups by blending a low molecular weight poly(ε-caprolactone)5k(PCL5k)containing orthogonally reactive azide groups with an unfunctionalized high molecular weight PCL75k at different ratios.Stable porous three-dimensional(3D)scaf-folds were then fabricated using a high weight percentage(75 wt.%)of the low molecular weight PCL 5k.As a proof-of-concept test,we prepared films of three different mass ratios of low and high molecular weight polymers with a thermopress and reacted with an alkynated fluorescent model compound on the surface,yielding a density of 201-561 pmol/cm^(2).Subsequently,a bone morphogenetic protein 2(BMP-2)-derived peptide was grafted onto the films comprising different blend compositions,and the effect of peptide surface density on the osteogenic differentiation of human mesenchymal stromal cells(hMSCs)was assessed.After two weeks of culturing in a basic medium,cells expressed higher levels of BMP receptor II(BMPRII)on films with the conjugated peptide.In addition,we found that alkaline phosphatase activity was only significantly enhanced on films contain-ing the highest peptide density(i.e.,561 pmol/cm^(2)),indicating the importance of the surface density.Taken together,these results emphasize that the density of surface peptides on cell differentiation must be considered at the cell-material interface.Moreover,we have presented a viable strategy for ME-AM community that desires to tune the bulk and surface functionality via blending of(modified)polymers.Furthermore,the use of alkyne-azide“click”chemistry enables spatial control over bioconjugation of many tissue-specific moieties,making this approach a versatile strategy for tissue engineering applications.

Tunable ciprofloxacin delivery through personalized electrospun patches for tympanic membrane perforations

Approximately 740 million symptomatic patients are affected by otitis media every year.Being an inflammatory disease affecting the middle ear,it is one of the primary causes of tympanic membrane(TM)perforations,often resulting in impaired hearing abilities.Antibiotic therapy using broad-spectrum fluoroquinolones,such as ciprofloxacin(CIP),is frequently employed and considered the optimal route to treat otitis media.However,patients often get exposed to high dosages to compensate for the low drug concentration reaching the affected site.Therefore,this study aims to integrate tissue engineering with drug delivery strategies to create biomimetic scaffolds promoting TM regeneration while facilitating a localized release of CIP.Distinct electrospinning(ES)modalities were designed in this regard either by blending CIP into the polymer ES solution or by incorporating nanoparticles-based co-ES/electrospraying.The combination of these modalities was investigated as well.A broad range of release kinetic profiles was achieved from the fabricated scaffolds,thereby offering a wide spectrum of antibiotic concentrations that could serve patients with diverse therapeutic needs.Furthermore,the incorporation of CIP into the TM patches demonstrated a favorable influence on their resultant mechanical properties.Biological studies performed with human mesenchymal stromal cells confirmed the absence of any cytotoxic or anti-proliferative effects from the released antibiotic.Finally,antibacterial assays validated the efficacy of CIP-loaded scaffolds in suppressing bacterial infections,highlighting their promising relevance for TM applications.

Magnetically responsive nanofibrous ceramic scaffolds for on-demand motion and drug delivery

Smart biomaterials,featuring not only bioactivity,but also dynamic responsiveness to external stimuli,are desired for biomedical applications,such as regenerative medicine,and hold great potential to expand the boundaries of the modern clinical practice.Herein,a magnetically responsive three-dimensional scaffold with sandwich structure is developed by using hydroxyapatite(HA)nanowires and ferrosoferric oxide(Fe_(3)O_(4))nanoparticles as building blocks.The magnetic HA/Fe_(3)O_(4) scaffold is fully inorganic in nature,but shows polymeric hydrogel-like characteristics including a 3D fibrous network that is highly porous(>99.7%free volume),deformable(50%deformation)and elastic,and tunable stiffness.The magnetic HA/Fe3O4 scaffold has been shown to execute multimodal motion upon exposure to an external magnetic field including shape transformation,rolling and somersault.In addition,we have demonstrated that the magnetic scaffold can serve as a smart carrier for remotely controlled,on-demand delivery of compounds including an organic dye and a protein.Finally,the magnetic scaffold has exhibited good biocompatibility,supporting the attachment and proliferation of human mesenchymal stromal cells,thereby showing great potential as smart biomaterials for a variety of biomedical applications.

3D-printed bioactive scaffolds from nanosilicates and PEOT/PBT for bone tissue engineering

Additive manufacturing(AM)has shown promise in designing 3D scaffold for regenerative medicine.However,many synthetic biomaterials used for AM are bioinert.Here,we report synthesis of bioactive nanocomposites from a poly(ethylene oxide terephthalate)(PEOT)/poly(butylene terephthalate)(PBT)(PEOT/PBT)copolymer and 2D nanosilicates for fabricating 3D scaffolds for bone tissue engineering.PEOT/PBT have been shown to support calcification and bone bonding ability in vivo,while 2D nanosilicates induce osteogenic differentiation of human mesenchymal stem cells(hMSCs)in absence of osteoinductive agents.The effect of nanosilicates addition to PEOT/PBT on structural,mechanical and biological properties is investigated.Specifically,the addition of nanosilicate to PEOT/PBT improves the stability of nanocomposites in physiological conditions,as nanosilicate suppressed the degradation rate of copolymer.However,no significant increase in the mechanical stiffness of scaffold due to the addition of nanosilicates is observed.The addition of nanosilicates to PEOT/PBT improves the bioactive properties of AM nanocomposites as demonstrated in vitro.hMSCs readily proliferated on the scaffolds containing nanosilicates and resulted in significant upregulation of osteo-related proteins and production of mineralized matrix.The synergistic ability of nanosilicates and PEOT/PBT can be utilized for designing bioactive scaffolds for bone tissue engineering.