BackgroundThe potential medical applications of nanomaterials are shaping the landscape of the nanobiotechnology field and driving it forward. A key factor in determining the suitability of these nanomaterials must be how they interface with biological systems. Single walled carbon nanotubes (CNT) are being investigated as platforms for the delivery of biological, radiological, and chemical payloads to target tissues. CNT are mechanically robust graphene cylinders comprised of sp2-bonded carbon atoms and possessing highly regular structures with defined periodicity. CNT exhibit unique mechanochemical properties that can be exploited for the development of novel drug delivery platforms. In order to evaluate the potential usefulness of this CNT scaffold, we undertook an imaging study to determine the tissue biodistribution and pharmacokinetics of prototypical DOTA-functionalized CNT labeled with yttrium-86 and indium-111 (86Y-CNT and 111In-CNT, respectively) in a mouse model.Methodology and Principal FindingsThe 86Y-CNT construct was synthesized from amine-functionalized, water-soluble CNT by covalently attaching multiple copies of DOTA chelates and then radiolabeling with the positron-emitting metal-ion, yttrium-86. A gamma-emitting 111In-CNT construct was similarly prepared and purified. The constructs were characterized spectroscopically, microscopically, and chromatographically. The whole-body distribution and clearance of yttrium-86 was characterized at 3 and 24 hours post-injection using positron emission tomography (PET). The yttrium-86 cleared the blood within 3 hours and distributed predominantly to the kidneys, liver, spleen and bone. Although the activity that accumulated in the kidney cleared with time, the whole-body clearance was slow. Differential uptake in these target tissues was observed following intraveneous or intraperitoneal injection.ConclusionsThe whole-body PET images indicated that the major sites of accumulation of activity resulting from the administration of 86Y-CNT were the kidney, liver, spleen, and to a much less extent the bone. Blood clearance was rapid and could be beneficial in the use of short-lived radionuclides in diagnostic applications.
There has been considerable interest in recent years in using metal, semiconductor, and magnetic nanoparticles in biological applications. [1][2][3][4][5][6][7] A wide range of ligation and encapsulation methods have been developed to render the nanoparticles soluble in aqueous solution, to prevent aggregation, and to provide means by which functional molecules can be attached. Among these methods, encapsulation of nanoparticles by a polymer, [8,9] phospholipid, [10] or inorganic [11,12] shell is of particular interest to us, since these stable shells prevent dissociation of surface ligands and provide anchor points where biomolecules are unlikely to be lost once attached. This is a significant advantage over direct conjugation through surface ligands, since even strong thiol ligands can dissociate from or undergo exchange on gold surfaces, [13] let alone weaker ligands on the surfaces of quantum dots or magnetic nanoparticles. Stable attachment of biomolecules would be particularly important where only a few biomolecules are selectively attached to a nanoparticle, or when multiple types of singly functionalized nanoparticles are mixed.Stable functionalization of quantum dots remains a challenge. While biomolecules have been attached to quantum dots and used for biological studies, [4,5] a nondissociable ligand shell would be required for attachment of biomolecules selectively and with controlled valency. Recently, Taton et al. reported encapsulation of gold nanoparticles (AuNPs) [14,15] and magnetic nanoparticles (MagNPs) [16,17] by amphiphilic diblock copolymers. The resulting nanoparticles have a stable, well-defined core/shell structure impermeable to ionic species in aqueous solution. Such a polymer shell would be ideal for functionalization of quantum dots if a similar encapsulation methodology could be adopted. However, it was found that in this system small (d < 10 nm) AuNPs and MagNPs act as solutes in polymer micelles and are therefore prone to multiple inclusion on encapsulation. [14] In contrast, large AuNPs act as surface templates on which polymer molecules assemble into micellar shells that each encapsulate a single AuNP. Since most nanoparticles used for biological studies, particularly quantum dots, have diameters in the range of 2-9 nm, it is necessary that we develop new methods that can encapsulate single nanoparticles of sizes similar to quantum dots.Herein we report the encapsulation of single small AuNPs, in preparation for future work on quantum dots, since AuNPs are easier to handle and characterize. Diblock copolymers such as PS 108 PGA 108 , PS 132 PAA 72 , and PS 159 PAA 62 [PS: polystyrene, PGA: poly(glutamic acid), PAA: poly(acrylic acid)] were used to encapsulate AuNPs in "hairy" micelles (Figure 1 B); the resulting core/shell nanoparticles are stable in solution without chemical crosslinking. The long hydrophilic blocks of the polymers were initially chosen to help stabilize attached biomolecules, but were later found to allow encapsulation of single small AuNPs. The use of such po...
Cartilage repair presents a daunting challenge in tissue engineering applications due to the low oxygen conditions (hypoxia) affiliated in diseased states. Hence, the use of biomaterial scaffolds with unique variability is imperative to treat diseased or damaged cartilage. Thermosensitive hydrogels show promise as injectable materials that can be used as tissue scaffolds for cartilage tissue regeneration. However, uses in clinical applications are limited to due mechanical stability and therapeutic efficacy to treat diseased tissue. In this study, several composite hydrogels containing poly(N-vinylcaprolactam) (PVCL) and methacrylated hyaluronic acid (meHA) were prepared using free radical polymerization to produce PVCL-graft-HA (PVCL-g-HA) and characterized using Fourier transform infrared spectroscopy, nuclear magnetic resonance, and scanning electron microscopy. Lower critical solution temperatures and gelation temperatures were confirmed in the range of 33-34°C and 41-45°C, respectively. Using dynamic sheer rheology, the temperature dependence of elastic (G') and viscous (G″) modulus between 25°C and 45°C, revealed that PVCL-g-HA hydrogels at 5% (w/v) concentration exhibited the moduli of 7 Pa (G') to 4 Pa (G″). After 10 days at 1% oxygen, collagen production on PVCL-g-HA hydrogels was 153 ± 25 μg/mg (20%) and 106 ± 18 μg/mg showing a 10-fold increase compared to meHA controls. These studies show promise in PVCL-g-HA hydrogels for the treatment of diseased or damaged articular cartilage. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1863-1873, 2017.
Temperature‐responsive PVCL homopolymers and functional PVCL polymers containing carboxylic acids are prepared in organic and aqueous solutions. PVCL bulk polymers are characterized using 1H NMR, photometry, ATR‐FTIR, and thermal analysis. A finite phase transition at 37–40 °C occurs in aqueous solutions of PVCL and PVCL‐COOH. PVCL and PVCL‐COOH polymers are electrospun into fibers ranging from 100 to 2300 nm in diameter. PVCL/cellulose bi‐component films are obtained by electrospinning of CA and PVCL followed by alkaline hydrolysis. These tunable thermo‐responsive PVCL/cellulose nanofibers have potential applications in developing affinity membranes.
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