Prospective clinical and radiographic evaluation of an allogeneic bone matrix containing stem cells (Trinity Evolution® Viable Cellular Bone Matrix) in patients undergoing two-level anterior cervical discectomy and fusion.

BACKGROUND: Trinity Evolution® (TE), a viable cellular bone allograft, previously demonstrated high fusion rates and no safety-related concerns after single-level anterior cervical discectomy and fusion (ACDF) procedures. This prospective multicenter clinical study was performed to assess the radiographic and clinical outcomes of TE in subjects undergoing two-level ACDF procedures. METHODS: In a prospective, multicenter study, 40 subjects that presented with symptomatic cervical degeneration at two adjacent vertebral levels underwent instrumented ACDF using TE autograft substitute in a polyetherethereketone (PEEK) cage. At 12 months, radiographic fusion status was evaluated by dynamic motion plain radiographs and thin cut CT with multiplanar reconstruction by a panel that was blinded to clinical outcome. Fusion success was defined by angular motion (≤4°) and the presence of bridging bone across the adjacent vertebral endplates. Clinical pain and function assessments included the Neck Disability Index (NDI), neck and arm pain as evaluated by visual analog scales (VAS), and SF-36 at both 6 and 12 months. RESULTS: At both 6 and 12 months, all clinical outcome scores (SF-36, NDI, and VAS pain) improved significantly (p < 0.05) compared to baseline values. There were no adverse events or infections that were attributed to the graft material, no subjects that required revisions, and no significant decreases to mean neurological evaluations at any time as compared to baseline. At 12 months, the per subject and per level fusion rate was 89.4 and 93.4%, respectively. Subgroup analysis of subjects with risk factors for pseudoarthrosis (current or former smokers, diabetic, or obese/extremely obese) compared to those without risk factors demonstrated no significant differences in fusion rates. CONCLUSIONS: Patients undergoing two-level ACDF with TE in combination with a PEEK interbody spacer and supplemental anterior fixation had a high rate of fusion success without any serious adverse events related to the graft material. TRIAL REGISTRATION: Trinity Evolution in Anterior Cervical Disectomy and Fusion (ACDF) NCT00951938.

A prospective clinical and radiographic 12-month outcome study of patients undergoing single-level anterior cervical discectomy and fusion for symptomatic cervical degenerative disc disease utilizing a novel viable allogeneic, cancellous, bone matrix (trinity evolution™) with a comparison to historical controls.

PURPOSE: This multicenter clinical study was performed to assess the safety and effectiveness of Trinity Evolution(®) (TE), a viable cellular bone allograft, in combination with a PEEK interbody spacer and supplemental anterior fixation in patients undergoing anterior cervical discectomy and fusion (ACDF). METHODS: In a prospective, multi-center study, 31 patients that presented with symptomatic cervical degeneration at one vertebral level underwent ACDF with a PEEK interbody spacer (Orthofix, Inc., Lewisville, TX, USA) and supplemental anterior fixation. In addition all patients had the bone graft substitute, Trinity Evolution (Musculoskeletal Transplant Foundation, Edison, NJ, USA), placed within the interbody spacer. At 6 and 12 months, radiographic fusion was evaluated as determined by independent radiographic review of angular motion (≤4°) from flexion/extension X-rays combined with presence of bridging bone across the adjacent endplates on thin cut CT scans. In addition other metrics were measured including function as assessed by the Neck Disability Index (NDI), and neck and arm pain as assessed by individual Visual Analog Scales (VAS). RESULTS: The fusion rate for patients using a PEEK interbody spacer in combination with TE was 78.6 % at 6 months and 93.5 % at 12 months. When considering high risk factors, 6-month fusion rates for patients that were current or former smokers, diabetic, overweight or obese/extremely obese were 70 % (7/10), 100 % (1/1), 70 % (7/10), and 82 % (9/11), respectively. At 12 months, the fusion rates were 100 % (12/12), 100 % (2/2), 100 % (11/11) and 85 % (11/13), respectively. Neck function, and neck/arm pain were found to significantly improve at both time points. No serious allograft related adverse events occurred and none of the 31 patients had subsequent additional cervical surgeries. CONCLUSIONS: Patients undergoing single-level ACDF with TE in combination with a PEEK interbody spacer and supplemental anterior fixation had a high rate of fusion success without serious allograft-related adverse events.

Inhibitory effects of a phage-derived peptide on Au nanocrystal nucleation and growth.

Peptides have been shown to mediate the reduction and clustering of inorganic ions during biomineralization processes to build nanomaterials with well-defined shape, size, and composition. This precise control has been linked to specific amino acid sequence; however, there is a lack of information about the role of peptides during mineralization. Here, we investigate the nucleation and growth behavior of Au nanocrystals that are mediated by the engineered peptide AYSSGAPPMPPF. Unlike other nanocrystal synthesis schemes, this peptide produces Au nanocrystals from Au(III) ions at very low relative peptide concentrations, at ambient temperature, and in water at neutral pH. Our data show that (i) the peptide AYSSGAPPMPPF actually inhibits nucleation and growth of nanocrystals, (ii) HEPES plays an active chemical role as the reducing agent, and (iii) HAuCl4 accelerates the kinetics of nanoparticle nucleation and growth. Herein, we propose empirical rate laws for nucleation and growth of Au nanocrystals and compare kinetic rate laws for this peptide, citrate, and various other polymer ligands. We find that the peptide belongs to a unique class of nonreducing inhibitor ligands regulating the surface-reaction-limited growth of nanocrystals.

SERS not to be taken for granted in the presence of oxygen.

Oxidation of the Ag nanoparticle surface has a dramatic effect on the adsorption, orientation, and SERS detection limit of nitroaromatic molecules in aqueous solutions. Ultrasensitive SERS detection of p-nitrophenol can be achieved when oxidation of surface-immobilized Ag nanoparticles is inhibited by replacing the oxygen dissolved in water with argon gas. The presence of silver oxide at the nanoparticle surface hinders charge transfer between the aromatic ring and the underlying Ag metal surface and drastically decreases the overall detection sensitivity.

Langmuir adsorption study of the interaction of CdSe/ZnS quantum dots with model substrates: influence of substrate surface chemistry and pH.

We investigate the utility of Langmuir adsorption measurements for characterizing nanoparticle-substrate interactions. Spherical CdSe/ZnS core-shell nanoparticles were chosen as representative particles because of their widespread use in biological labeling measurements and their relatively monodisperse dimensions. In particular, the quantum dots were functionalized with 11-mercaptoundecanoic acid, and we utilized an amine-terminated self-assembled monolayer (SAM) as a model substrate. SAMs with different end-groups (-CH(3) and -COOH) were also considered to contrast with the adsorption behavior on the amine-terminated SAM substrates. We followed the kinetics of nanoparticle adsorption on the aminosilane layer by quartz crystal microgravimetry (QCM) over a range of particle concentrations and determined the corresponding Langmuir adsorption isotherms. Analysis of both equilibrium adsorption and kinetic adsorption data allowed us to determine a consistent value of the Langmuir adsorption equilibrium constant for the amine-terminated SAM at room temperature (K(L) approximately 2.7 (micromol/L)(-1)), providing a useful characterization of the nanoparticle-substrate interaction. The effect of varying solution pH on Langmuir adsorption was also investigated in order to gain insight into the role of electrostatic interactions on nanoparticle adsorption. The equilibrium extent of adsorption was found to be maximum at about pH 7. These changes of nanoparticle adsorption were further quantified and validated by X-ray photoelectron spectroscopy (XPS) and confocal fluorescence microscopy measurements. We conclude that Langmuir adsorption measurements provide a promising approach for quantifying nanoparticle-substrate interactions.

Flexion-extension response of the thoracolumbar spine under compressive follower preload.

STUDY DESIGN: The authors conducted an in vitro biomechanical flexibility study of T2-S1 specimens in flexion-extension under compressive follower preloads of physiological magnitudes. OBJECTIVES: The objectives of this study were to test the hypotheses that 1) the thoracolumbar spine will support compressive preloads of in vivo magnitudes and 2) allow physiological mobility under flexion-extension moments if the preload is applied along an optimized follower load path that approximates the kypholordotic curve of the thoracolumbar spine. SUMMARY OF BACKGROUND DATA: In the absence of muscle forces, the ligamentous thoracolumbar spine specimens cannot support the compressive loads expected in vivo. As a result, the flexibility of the thoracolumbar spine in flexion-extension has not been studied in vitro under physiological compressive preloads. METHODS: Seven human thoracolumbar spines (T2-sacrum) were subjected to flexion and extension moments (up to 8 and 6 Nm, respectively) under compressive preloads from 0 to 800 N applied along an optimized follower preload path. The experimental technique applied the compressive preload such that: 1) it minimized the internal shear forces and bending moments resulting from the preload application, 2) made the internal force resultant compressive, and 3) caused the preload path to approximate the tangent to the curve of the thoracolumbar spine. The range of motion was measured in the T2-sacrum, T2-T11, T11-L1, and L1-sacrum regions. RESULTS: All thoracolumbar specimens supported the compressive follower preload up to 800 N without damage or instability. At 800 N preload, the total flexion-extension range of motion of the T2-sacrum region decreased by 22%, from a mean of 73 degrees to 57 degrees (P < 0.05). The range of motion of the T2-T11 and L1-sacrum regions decreased from the baseline value by 23% and 30%, respectively, at a preload of 800 N. The sagittal mobility of the thoracolumbar junction (T11-L1) was not affected by the preload. The follower preload did not significantly affect the proportion of the total T2-sacrum flexion-extension range of motion contributed by the T2-T11 and L1-sacrum regions of the thoracolumbar spine. CONCLUSIONS: The optimized follower preload vector minimizes the effects of artifact moment and shear force on the range of motion of the thoracolumbar spine in flexion-extension. This model allows the entire thoracolumbar spine to be investigated under physiological loading for different clinical applications.