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Three-dimensional porous scaffolds prepared from regenerated silk fibroin using either an all aqueous process or a process involving an organic solvent, hexafluoroisopropanol (HFIP) have shown promise in cell culture and tissue engineering applications. However, their biocompatibility and in vivo degradation has not been fully established. The present study was conducted to systematically investigate how processing method (aqueous vs. organic solvent) and processing variables (silk fibroin concentration and pore size) affect the short-term (up to 2 months) and longterm (up to 1 year) in vivo behavior of the protein scaffolds in both nude and Lewis rats. The samples were analyzed by histology for scaffold morphological changes and tissue ingrowth, and by real-time RT-PCR and immunohistochemistry for immune responses. Throughout the period of implantation, all scaffolds were well-tolerated by the host animals and immune responses to the implants were mild. Most scaffolds prepared from the all aqueous process degraded to completion between two and six months, while those prepared from organic solvent (hexafluoroisopropanol (HFIP)) process persisted beyond one year. Due to widespread cellular invasion throughout the scaffold, the degradation of aqueous-derived scaffolds appears to be more homogeneous than that of HFIP-derived scaffolds. In general and especially for the HFIP-derived scaffolds, a higher original silk fibroin concentration (e.g. 17%) and smaller pore size (e.g. 100-200 µm) resulted in lower levels of tissue ingrowth and slower degradation. These results demonstrate that the in vivo behavior of the three-dimensional silk fibroin scaffolds is related to the morphological and structural features that resulted from different scaffold preparation processes. The insights gained in this study can serve as a guide for processing scenarios to match desired morphological and structural features and degradation time with tissue-specific applications.

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Peptide nanostructures are biodegradable and are suitable for many biomedical applications. However, to be useful imaging probes, the limited intrinsic optical properties of peptides must be overcome. Here we show the formation of tryptophan-phenylalanine dipeptide nanoparticles (DNPs) that can shift the peptide's intrinsic fluorescent signal from the ultraviolet to the visible range. The visible emission signal allows the DNPs to act as imaging and sensing probes. The peptide design is inspired by the red shift seen in the yellow fluorescent protein that results from π-π stacking and by the enhanced fluorescence intensity seen in the green fluorescent protein mutant, BFPms1, which results from the structure rigidification by Zn(II). We show that DNPs are photostable, biocompatible and have a narrow emission bandwidth and visible fluorescence properties. DNPs functionalized with the MUC1 aptamer and doxorubicin can target cancer cells and can be used to image and monitor drug release in real time.

Background-Phase 1 clinical trials of granulocyte-colony stimulating factor (G-CSF) treatment after myocardial infarction have indicated that G-CSF treatment is safe and may improve left ventricular function. This randomized, double-blind, placebo-controlled trial aimed to assess the efficacy of subcutaneous G-CSF injections on left ventricular function in patients with ST-elevation myocardial infarction. Methods and Results-Seventy-eight patients (62 men; average age, 56 years) with ST-elevation myocardial infarction were included after successful primary percutaneous coronary stent intervention Ͻ12 hours after symptom onset. Patients were randomized to double-blind treatment with G-CSF (10 g/kg of body weight) or placebo for 6 days. The primary end point was change in systolic wall thickening from baseline to 6 months determined by cardiac magnetic resonance imaging (MRI). An independent core laboratory analyzed all MRI examinations. Systolic wall thickening improved 17% in the infarct area in the G-CSF group and 17% in the placebo group (Pϭ1.0). Comparable results were found in infarct border and noninfarcted myocardium. Left ventricular ejection fraction improved similarly in the 2 groups measured by both MRI (8.5 versus 8.0; Pϭ0.9) and echocardiography (5.7 versus 3.7; Pϭ0.7). The risk of severe clinical adverse events was not increased by G-CSF.In addition, in-stent late lumen loss and target vessel revascularization rate in the follow-up period were similar in the 2 groups. Conclusions-Bone marrow stem cell mobilization with subcutaneous G-CSF is safe but did not lead to further improvement in ventricular function after acute myocardial infarction compared with the recovery observed in the placebo group.

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