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In this study, we present the fabrication and characterization of the kink-free electrospun small caliber (4 mm in internal diameter) vascular graft based on a blend of biocompatible poly(ethylene terephthalate) (PET) and highly elastomeric polyurethane (PU) and subsequently reinforced by additive manufacturing 3D printing. We also report the design and simulation of the grafts under various internal pressures. Long-length small-diameter grafts suffer from the kink and loop formation for electrospun tubes. We have seen that collector rotation speeds (from 50 to 200 rpm) yielded grafts with varied mechanical properties and kink resistance. By reinforcing electrospun vascular grafts with the help of 3D printing, we report the reduction of the kink radius from 2.30 to 0.45 cm and 0.57 cm, respectively, for poly(lactic acid) (PLA)- and PET-reinforced vascular graft.

Hemorrhagic blood loss from traumatic injury is the leading cause of death in severe accidents and combat injuries. Treating and stopping blood loss in a timely and effective manner is essential for the survival of the patient. Currently, QuikClot and dry fibrin sealant dressing are well-known approaches for hemostatic treatment. However, these dressings have limitations in slowing blood loss such as being brittle, low blood absorption, and a poor sealant of the injury site. Temperature-sensitive gels may have potential as a platform for delivery of coagulation factors to improve hemostasis and wound sealing in the treatment of traumatic injuries. Here, we developed a temperature-sensitive triblock copolymer (poly ethylene oxide (PEO)-poly propylene oxide (PPO)-poly ethylene oxide (PEO)) containing fibrinogen to promote blood coagulation through gel formation at body temperature. This temperature sensitive solution-to-gel (sol-gel) transition does not require cross-linking agents or UV photoinitiation. We determined that 22 wt % (weight percent) copolymers with and without fibrinogen was the maximum concentration for sol-gel transition at body temperature. Rheology results further confirmed this sol-gel transition of 22 wt % copolymers at body temperature. We showed that fibrinogen itself promoted blood coagulation. Additionally, 22 wt % copolymer with fibrinogen successfully demonstrated stable blood coagulation within the gel compared to 22 wt % copolymer without fibrinogen. Twenty-two weight percent copolymers with and without fibrinogen also exhibited excellent biocompatibility based on cell viability, proliferation, and morphology analysis. In addition, treatment of 22 wt % copolymers did not stimulate pro-inflammatory TNF-α production from differentiated human monocytes. Our results suggest that 22 wt % of a temperature-sensitive copolymer gel containing fibrinogen has great potential as a hemostatic agent stimulating coagulation and providing immediate wound coverage for protection through a sol-gel transition at body temperature.

Peptides with proper sequences are capable of self-assembling into well-defined nanostructures, which can subsequently grow and entangle into three-dimensional nanomatrices. In this study, hemopressin, a cannabinoid receptor-modulating peptide derived from the α-chain of hemoglobin known to self-assemble into nanofibrils, was examined for its potential applicability as a gelator. The results indicated that hemopressin’s gel formation was dependent on pH and salt concentration. Although hemopressin’s macroscopic states showed differences, its microscopic structure remained largely unchanged in which it consisted mainly of the antiparallel β-sheet conformation as confirmed by FTIR (C=O stretch peaks at 1630 and 1695 cm–1) and CD (β-sheet peak at 195 nm). The major difference between the gel and sol states was displayed in the fibril length in which the gelation at pH 7.4 resulted in 4 μm fibrils, whereas the solution at pH 5.0 showed 800 nm fibrils. The pH-dependent sol–gel phase transition property was the...

The field of nanomedicine has been expanding rapidly in the recent decades that opened the current century. Specifically, nanogels comprise an interesting subset of the nanomedicine design space. A brief overview of the general field of nanotechnology will be introduced and discussion on the role of nanogels. A brief state of the start for applications of magnetic and fluorescent properties and the combination of both are discussed specifically as applied to nanogels. Finally, opinions on the current challenges and future opportunities are discussed with regard to nanogel applications in nanomedicine. Herein, this chapter summarizes some of the important fundamental fields related to this topic and how nanogels intersect other important areas specifically targeting healthcare applications.

We report a novel and facile organosilane plasma polymerization method designed to improve the surface characteristics of poly(tetrafluoroethylene) (PTFE). We hypothesized that the polymerized silane coating would provide an adhesive surface for endothelial cell proliferation due to a large number of surface hydroxyl groups, while the large polymer networks on the surface of PTFE would hinder platelet attachment. The plasma polymerized PTFE surfaces were then systematically characterized via different analytical techniques such as FTIR, XPS, XRD, Contact angle, and SEM. The key finding of the characterization is the time-dependent deposition of an organosilane layer on the surface of PTFE. This layer was found to provide favorable surface properties to PTFE such as a very high surface oxygen content, high hydrophilicity and improved surface mechanics. Additionally, in vitro cellular studies were conducted to determine the bio-interface properties of the plasma-treated and untreated PTFE. The important results of these experiments were rapid endothelial cell growth and decreased platelet attachment on the plasma-treated PTFE compared to untreated PTFE. Thus, this new surface modification technique could potentially address the current challenges associated with PTFE for blood contact applications, specifically poor endothelial cell growth and risk of thrombosis.

We report a method to increase the efficiency of radio-frequency (RF) generated plasma for surface modification of electrospun biomaterials by introducing magnetization. The x-ray photoelectron spectroscopy (XPS) reveals the oxygen/carbon ratio is consistently higher for various exposure times for magnetized plasma than non-magnetized plasma. The principle demonstrated here supports the use of magnetic fields as an additional controllable parameter in plasma processing of biomaterials and is extendable to other plasma sources. The surface activation and functionalization of biomaterials has impact in the broader arena of tissue engineering applications in that magneto-plasma processing (MPP) enables us to tune the shape of plasma plume for selective enhanced functionalization of surface of scaffolds, which in turn has wide applications for basic cell-patterning science and in applied regenerative medicine.

This chapter describes the current approaches toward small-diameter tissue-engineered vascular grafts. The outstanding problem of failure for grafts smaller than 4 mm diameter remains a challenge and requires a multidisciplinary approach. The perspectives of tissue engineering, surface modification, bioengineering, and emerging technology are discussed. The unifying themes are to mimic the native extracellular matrix, provide a favorable surface for cell proliferation, and develop a functional and confluent blood-contact surface. Continued efforts to produce a demonstrably functional small-diameter vascular graft are desperately needed.

Superhydrophobic surfaces have gained increased attention due to the high water-repellency and self-cleaning capabilities of these surfaces. In the present study, we explored a novel hybrid method of fabricating superhydrophobic poly(tetrafluoroethylene) (PTFE) surfaces by combining the physical etching capability of oxygen plasma with the plasma-induced polymerization of a organic monomer methyl methacrylate (MMA). This novel hybrid combination of oxygen-MMA plasma has resulted in the generation of superhydrophobic PTFE surfaces with contact angle of 154°. We hypothesized that the generation of superhydrophobicity may be attributed to the generation of fluorinated poly(methyl methacrylate) (PMMA) moieties formed by the combined effects of physical etching causing de-fluorination of PTFE and the subsequent plasma polymerization of MMA. The plasma treated PTFE surfaces were then systematically characterized via XPS, FTIR, XRD, DSC and SEM analyses. The results have clearly shown a synergistic effect of the oxygen/MMA combination in comparison with either the oxygen plasma alone or MMA vapors alone. Furthermore, the reported new hybrid combination of Oxygen-MMA plasma has been demonstrated to achieve superhydrophobicity at lower power and short time scales than previously reported methods in the literature. Hence the reported novel hybrid strategy of fabricating superhydrophobic PTFE surfaces could have futuristic potential towards biointerface applications.

Boron-rich B-C compounds with high hardness have been recently synthesized by the chemical vapor deposition (CVD) method. In this paper, we present our successful efforts in the selective growth of microstructures of boron-carbon compounds on silicon substrates. This was achieved by combining microfabrication techniques such as maskless lithography and sputter deposition with the CVD technique. Our characterization studies on these B-C microstructures showed that they maintain structural and mechanical properties similar to that of their thin-film counterparts. The methodology presented here paves the way for the development of microstructures for microelectromechanical system (MEMS) applications which require custom hardness and strength properties. These hard B-C microstructures are an excellent choice as support structures in MEMS-based devices.

Traditional wet chemistry offers a great magnitude of methods for surface modification and surface coatings for nanostructured materials. However, most methods require solvents and purification steps, and generate waste and byproducts. An interesting alternative set of methods involves the use of nonthermal or low-temperature plasmas (LTP) toward making and modifying nanostructured biomaterials. In this current opinion piece, some of the recent literature in this area is highlighted, and current perspectives are given. Emphasis is noted for the role of LTP for surface modification of nanofibrous scaffolds and plasma electrolytic oxidation (PEO) for surface-nanostructuring of metallic implants. The morphological nanofeaturing in fibrous mats as an extracellular matrix mimicking scaffold is presented along with recent perspectives of using LTP and plasma electrolytic oxidation for surface structuring for enhanced biointegration via cell/surface interactions with plasma processed implants/scaffolds constructs.

For several decades, plasma processing has been employed in the areas of food processing, manufacturing, and agriculture. Plasma processing has also been recognized as greatly beneficial in the field of tissue engineering for the modification of biomaterials. Polyethylene terephthalate (PET) has been employed as a vascular graft material but fails in small diameter applications. In this work, a multifaceted approach combining electrospinning to produce nano- and microscale fibers from PET blended with polybutylene terephthalate (PBT) added for flexibility and plasma modification for enhancing the surface chemistry is demonstrated to be an efficient approach to increase the biocompatibility as evidenced by enhanced fibroblast growth. The analysis of the surface chemistry shows an increase in oxygenated surface functionality, while the bulk analysis shows no significant changes. Thus, an efficient methodology for producing PET/PBT-based grafts that are easily modified with low-temperature plasma and show enhanced biocompatibility for vascular tissue engineering applications is reported.

Atmospheric pressure plasma jet (APPJ) based modification as a facile method to modify the intimal surface of small caliber nanofibrous tubular tissue scaffolds for potential use as vascular-graft or spinal-cord conduit is reported here. Polycaprolactone, a biomaterial used in the US Food and Drug Administration approved scaffolds for various tissue regeneration and bioabsorbable suture applications, was electrospun into thin nano/microfibers to form seamless three-dimensional (3D) conduits of 4 mm intimal diameter. The 3D conduits were subjected to treatment with an APPJ produced by dielectric barrier discharge using controlled gas flow into ambient atmosphere. He/air or He/air/NH3 gas mixtures combined with 8.5 kV pulsed direct current signal proved effective in creating a sustained and reactive cold plasma jet to modify the intimal surface of tubular scaffolds without affecting its biomechanical properties. The treatment resulted in surface chemistry modification as indicated by enrichment of oxygenated functional groups. Surface chemistry was determined via x-ray photoelectron spectroscopy. Scanning electron microscopy and glycerol contact angle measurements were used to determine the surface morphology and surface wettability. The data support the conclusion that APPJ is as an effective, facile, and robust approach to modify the intimal surface of small-caliber (