We present a simple and effective method to obtain refined control of the molecular structure of silk biomaterials through physical temperature-controlled water vapor annealing (TCWVA). The silk materials can be prepared with control of crystallinity, from a low content using conditions at 4°C (alpha-helix dominated silk I structure), to highest content of ~60% crystallinity at 100°C (beta-sheet dominated silk II structure). This new physical approach covers the range of structures previously reported to govern crystallization during the fabrication of silk materials, yet offers a simpler, green chemistry, approach with tight control of reproducibility. The transition kinetics, thermal, mechanical, and biodegradation properties of the silk films prepared at different temperatures were investigated and compared by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), uniaxial tensile studies, and enzymatic degradation studies. The results revealed that this new physical processing method accurately controls structure, in turn providing control of mechanical properties, thermal stability, enzyme degradation rate, and human mesenchymal stem cell interactions. The mechanistic basis for the control is through the temperature controlled regulation of water vapor, to control crystallization. Control of silk structure via TCWVA represents a significant improvement in the fabrication of silk-based biomaterials, where control of structure-property relationships is key to regulating material properties. This new approach to control crystallization also provides an entirely new green approach, avoiding common methods which use organic solvents (methanol, ethanol) or organic acids. The method described here for silk proteins would also be universal for many other structural proteins (and likely other biopolymers), where water controls chain interactions related to material properties.

No abstract

Therapeutic, III.

Hepatocellular carcinoma (HCC) is the most common primary liver tumor and is currently the leading indication for liver transplantation in the United States. Liver transplantation may provide a curative option for patients with HCC, but some present outside of the transplant criteria. Additionally, as the criteria for liver transplant eligibility in HCC are expanded and the incidence of disease increases, waitlist times are becoming progressively longer, which increases the chance of a patient suffering from disease progression while awaiting an organ becoming ineligible for transplant. Multiple studies have demonstrated the successful use of locoregional therapies, including trans-arterial chemoembolization and trans-arterial radioembolization, in downstaging HCC to within transplant criteria, as well as in preventing progression of disease in patients already listed for transplant. Cirrhotic patients also commonly develop portal vein thrombosis (PVT), which is a contraindication to transplantation at many centers. PVT can lead to worsened outcomes after transplant depending on the type of portal venous reconstruction that is performed. The purpose of this article is to discuss the integral role of interventional radiology in the care of these patients, including the role of transarterial therapies in the pretransplant treatment of HCC and the use of endovascular techniques to recanalize thrombosed portal veins in order to establish or maintain transplant eligibility.

Chronic venous insufficiency is a common and treatable medical condition which has a high morbidity if left untreated, progressing to lower extremity edema, skin changes of lipodermatosclerosis, and venous ulceration. Treatment options have significantly expanded over the last several decades, shifting away from the traditional surgical approach to more minimally invasive procedures such as endoluminal venous laser ablation or radiofrequency ablation. Even more recently, several techniques using nonthermal methods to ablate varicose veins have been developed, which offer the advantage of not requiring labor-intensive and painful tumescent anesthesia to protect the surrounding tissues. These techniques include mechanochemical ablation, cyanoacrylate closure, or polidocanol microfoam injection and can be offered to a wider range of patients without the need for sedation while offering similar closure rates and improved postprocedure symptom profile. Furthermore, certain patient characteristics which might preclude or complicate the use of thermal ablation methods might not pose a problem with nonthermal nontumescent methods.