The emergence of additive manufacturing has afforded the ability to fabricate intricate, high resolution, and patient‐specific polymeric implants. However, the availability of biocompatible resins with tunable resorption profiles remains a significant hurdle to clinical translation. In this study, 3D scaffolds are fabricated via stereolithographic cDLP printing of poly(propylene fumarate) (PPF) and assessed for bone regeneration in a rat critical‐sized cranial defect model. Scaffolds are printed with two different molecular mass resin formulations (1000 and 1900 Da) with narrow molecular mass distributions and implanted to determine if these polymer characteristics influence scaffold resorption and bone regeneration in vivo. X‐ray microcomputed tomography (µ‐CT) data reveal that at 4 weeks the lower molecular mass polymer degrades faster than the higher molecular mass PPF and thus more new bone is able to infiltrate the defect. However, at 12 weeks, the regenerated bone volume of the 1900 Da formulation is nearly equivalent to the lower molecular mass 1000 Da formulation. Significantly, lamellar bone bridges the defect at 12 weeks with both PPF formulations and there is no indication of an acute inflammatory response.
Immobilizing zwitterionic molecules on material surfaces has been a promising strategy for creating antifouling surfaces. Herein, we show the ability to surface derivatize an allylether-functionalized thermoplastic polyurethane (TPU) with a zwitterionic thiol in a radically induced thiol−ene reaction. The thermoplastic polyurethane was synthesized to have an allyl-ether side functionality using a modified chain extender molecule. The zwitterion surface functionalization was achieved via thiol−ene reaction in aqueous conditions. The presence of chemically tethered zwitterion moieties on the TPU surface was confirmed using X-ray photoelectron spectroscopy (XPS). Protein adsorption experiments via quartz crystal microbalance (QCM) show reduced fibrinogen attachment for the zwitterion-derivatized TPU when compared to its nonfunctionalized controls. The Zwitterion-TPU also showed a log scale reduction in bacterial adherence. For Pseudomonas aeruginosa and Staphylococcus epidermidis, the Zwitterion-TPU resulted in around a 40 and 50% lower bacterial biomass accumulation, respectively, over the time scale of the experiment. The fibroblast cell viability of TPU remained unaffected by functionalization with zwitterion thiol. The results from our model experiments suggest that a zwitterion-modified TPU is a promising candidate for antifouling catheters.
Poly(propylene fumarate) (PPF) has shown potential for the treatment of bone defects as it can be 3D printed into scaffolds to suit patient-specific needs with strength comparable to that of bone. However, the lack of specific cell attachment and osteogenic signaling moieties have limited their utility as it is necessary to provide these signals to aid in bone tissue formation. To address this issue and provide a platform for functionalization, Bioglass (∼1−2 μm) microparticles have been incorporated into PPF to create a 3D printable resin with concentrations ranging from 0 to 10 wt %. The zero-shear viscosity of PPF-Bioglass resins increased proportionally from 0 to 2.5 wt % Bioglass, with values of 0.22 and 0.34 Pa•s, respectively. At higher Bioglass concentrations, 5 and 10 wt %, the resin viscosity increased to 0.44 and 1.31 Pa•s, exhibiting a 2-and 6-fold increase from the 0 wt % Bioglass resin. Despite this increase in viscosity, all resins remained printable with no print failures. In addition, the surface available Bioglass can tether catechol containing molecules for postprinting functionalization. Analysis of PPF-Bioglass functionalization using a catechol dye analyte shows functionalization increases with Bioglass concentration, up to 157 nmol/ cm 2 , and demonstrates it is possible to modulate functionalization. This presents a versatile and highly translationally relevant strategy to functionalize 3D printed scaffolds post printing with a diverse array of functional species.
The use of polymers as excipients for drug delivery has afforded stable formulations that reliably control the release of active pharmaceutical ingredients (APIs). While many materials are available and used, few polymers exhibit the numerous advantages, including amorphous characteristics, noninflammatory properties, and resorbable degradation products, like those of poly(ester urea)s (PEUs). Furthermore, stability issues that arise in various APIs can make formulation optimization difficult. Herein, a series of PEUs were synthesized that vary by the fraction of l-phenylalanine monomer incorporated into the copolymerization. The various PEUs and entecavir monohydrate were dry-mixed at different weight percentages (15, 30, and 50%). Filaments of the PEU formulations were extruded and analyzed quantitatively for drug loading and content uniformity by using μ-CT and UPLC analysis. Drug dissolution profiles from filament segments were monitored over a 4-week period and ultimately showed that the controlled release of entecavir was influenced by the incorporation of the l-phenylalanine within the polymer.
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