Multifactor,Sequentially Releasing Scaffolds for Tissue Engineering:Fabrication Using Solvent/Nonsolvent Sintering Technology

Biodegradable constructs, providing both mechanical support to growing tissues and timed release of biological agents, are highly desired in tissue engineering. This study aimed to develop a platform technology that responds to these challenges. Accordingly, we report herein on model systems in which microspheres of poly(suberic anhydride), containing all-trans retinoic acid (atRA), and poly(d,l -lactic acid-co-glycolic acid), containing bovine serum albumin (BSA), were co-sintered at room temperature, using a solvent/nonsolvent mixture. These scaffolds release about 60% of atRA and negligible amounts of BSA within the first five days, followed by slower and steady release of BSA. They have pores of 150–500 μm and a compressive modulus of 200 kPa. Myoblasts and fibroblasts were seeded on the loaded scaffolds and both showed enhanced proliferation rates. Based on sound thermodynamic principles of polymer science, this technology demonstrates an as yet unachieved degree of versatility. It allows for the tailoring of “intelligent” scaffolds that preserve the integrity of the incorporated agents and of advanced modalities to release various drugs in a scheduled manner.     

Continuous separation of particles from macromolecules in split-flow thin (SPLITT) cells

A split-flow thin (SPLITT) cell with a perpendicular driving force of one gravity has been utilized for the rapid separation of micron-sized particles from macromolecules. The procedure involves the simultaneous use of two transport mechanisms and thus two operating modes: a sedimentation process controls the displacement of the particles across the thickness of the thin channel, while diffusion controls the displacement of macromolecules. The theoretical equations for these two operating modes are summarized and it is shown how the two modes can be combined to yield specified recovery factors. The theory was tested on a mixture of 10 μm polystyrene latex beads and three different proteins. The observed separation was in excellent agreement with theory. Attempts to fractionate red blood cells and plasma proteins from whole blood were only partially successful as a consequence of the weak sedimentation of red blood cells. Various remedies to this problem are suggested, the most promising of which is the use of a SPLITT cell subject to mild centrifugal forces.     

Good looks may help: Effects of helper's physical attractiveness and sex of helper on males' and females' help-seeking behavior.

96 19–21 yr old Ss were asked to solve a detective story and were under the impression that correct solutions could be obtained only after a specified number of preliminary questions were answered correctly. Some of these questions were unanswerable, and Ss could ask another S for help. In line with past research (E. Bercheid and E. Walster, 1974; A. Nadler, see PA, Vol 66:5817; H. Sigall and E. Aronson, PA, Vol 43:8310; S. Stokes and L. Bickman, PA, Vol 54:3045), data indicate that for same-sex others, Ss tended to seek less help from physically attractive than unattractive helpers. In cases of cross-sex helping (a) males sought less help from a physically attractive female than an unattractive female and (b) females sought more help from a physically attractive than an unattractive male. Findings are discussed in terms of a self-presentation approach to interpersonal help-seeking behavior. A model of help-seeking and self-presentation is presented. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adjustable spiral phase plate

A spiral phase retarder phi(r, theta) = mtheta has been constructed with use of a deformed cracked plexiglass plate. By changing the degree of deformation, the retarder can be adjusted for use at any wavelength, and the value of the phase step 2pim at theta = 2pi can be chosen.     

Stabilizing RNA by the sonochemical formation of RNA nanospheres

Biological macromolecules, including DNA, RNA, and proteins, have intrinsic features that make them potential building blocks for the bottom-up fabrication of nanodevices. Unlike DNA, RNA is a more versatile molecule whose range in the cell is from 21 to thousands of nucleotides and is usually folded into stem and loop structures. RNA is unique in nanoscale fabrication due to its diversity in size, function, and structure. Because gene expression analysis is becoming a clinical reality and there is a need to collect RNA in minute amounts from clinical samples, keeping the RNA intact is a growing challenge. RNA samples are notoriously difficult to handle because of their highly labile nature and tendency to degrade even under controlled RNase-free conditions and maintenance in the cold. Silencing the RNA that induces the RNA interference is viewed as the next generation of therapeutics. The stabilization and delivery of RNA to cells are the major concerns in making siRNAs usable drugs. For the first time, ultrasonic waves are shown to convert native RNA molecules to RNA nanospheres. The creation of the nanobubbles is performed by a one-step reaction. The RNA nanospheres are stable at room temperature for at least one month. Additionally, the nanospheres can be inserted into mammalian cancer cells (U2OS). This research achieves: 1) a solution to RNA storage; and 2) a way to convert RNA molecules to RNA particles. RNA nanosphere formation is a reversible process, and by using denaturing conditions, the RNA can be refolded into intact molecules.     

Field-Flow Fractionation (FFF) and Related Techniques for the Separation of Particles,Colloids and Macromolecules

Thin-channel flow techniques can be used for the separation of samples ranging over 15 orders of magnitude in molecular weight, namely, macromolecules, colloids, and particles. The first part describes the group of field-flow fractionation techniques. Flow system components are illustrated and described, as well as mode of operation and theory behind retention in the thin channel. An update of current topics under research is given, namely, normal retention mode of Brownian particles (under 1 μm in diameter) as compared to the steric retention mode of non-Brownian particles (above 1 μm in diameter). Optimization of the separation by field programming is briefly discussed. Another group of thin-channel techniques for small-scale processing, the split-flow thin (SPLITT) cells, in which fractionation is based on mass transport across the channel thickness, is presented in the second part. Principles of separation in this technology as well as possible applications are illustrated and discussed.     

Encapsulation of RNA Molecules in BSA Microspheres and Internalization into Trypanosoma Brucei Parasites and Human U2OS Cancer Cells

RNA was encapsulated in bovine serum albumin (BSA) microspheres using a one‐step sonochemical process from an water–oil solvent biphasic system. Confocal microcoscopy and fluorescence‐activated cell sorting indicate that a CY3‐RNA (RNA labeled with red fluorescent indocarbocyanine Cy3 dye) sphere is encapsulated in the BSA outer sphere. The diameter of the sphere depends on the number of nucleotides of the RNA, ranging from 0.63 to 2.74 μm. Total RNA (t‐RNA) was used as a prototype for the future small interfering RNA (siRNA) delivery. A very broad size distribution characterizes the RNA spheres and therefore, among the loaded BSA spheres, there were sufficiently small spheres to be successfully introduced into trypanosoma brucei parasites and human osteosarcoma U2OS cancer cells.     

The Role of Biomaterials in Peripheral Nerve and Spinal Cord Injury: A Review

Peripheral nerve and spinal cord injuries are potentially devastating traumatic conditions with major consequences for patients’ lives. Severe cases of these conditions are currently incurable. In both the peripheral nerves and the spinal cord, disruption and degeneration of axons is the main cause of neurological deficits. Biomaterials offer experimental solutions to improve these conditions. They can be engineered as scaffolds that mimic the nerve tissue extracellular matrix and, upon implantation, encourage axonal regeneration. Furthermore, biomaterial scaffolds can be designed to deliver therapeutic agents to the lesion site. This article presents the principles and recent advances in the use of biomaterials for axonal regeneration and nervous system repair.     

Engineered Vascularized Flaps,Composed of Polymeric Soft Tissue and Live Bone,Repair Complex Tibial Defects

Functional regeneration of complex large-scaled defects requires both soft- and hard-tissue grafts. Moreover, bone constructs within these grafts require an extensive vascular supply for survival and metabolism during the engraftment. Soft-tissue pedicles are often used to vascularize bony constructs. However, extensive autologous tissue-harvest required for the fabrication of these grafts remains a major procedural drawback. In the current work, a composite flap is fabricated using synthetic soft-tissue matrices and decellularized bone, combined in vivo to form de novo composite tissue with its own vascular supply. Pre-vascularization of the soft-tissue matrix using dental pulp stem cells (DPSCs) and human adipose microvascular endothelial cells (HAMECs) enhances vascular development within decellularized bones. In addition, osteogenic induction of bone constructs engineered using adipose derived mesenchymal stromal cells positively affects micro-capillary organization within the mineralized component of the neo-tissue. Eventually, these neo-tissues used as axial reconstructive flaps support long-term bone defect repair, as well as muscle defect bridging. The composite flaps described here may help eliminate invasive autologous tissue-harvest for patients in need of viable grafts for transplantation.     

sFasL—The Key to a Riddle: Immune Responses in Aging Lung and Disease

By dint of the aging population and further deepened with the Covid-19 pandemic, lung disease has turned out to be a major cause of worldwide morbidity and mortality. The condition is exacerbated when the immune system further attacks the healthy, rather than the diseased, tissue within the lung. Governed by unremittingly proliferating mesenchymal cells and increased collagen deposition, if inflammation persists, as frequently occurs in aging lungs, the tissue develops tumors and/or turns into scars (fibrosis), with limited regenerative capacity and organ failure. Fas ligand (FasL, a ligand of the Fas cell death receptor) is a key factor in the regulation of these processes. FasL is primarily found in two forms: full length (membrane, or mFasL) and cleaved (soluble, or sFasL). We and others found that T-cells expressing the mFasL retain autoimmune surveillance that controls mesenchymal, as well as tumor cell accumulation following an inflammatory response. However, mesenchymal cells from fibrotic lungs, tumor cells, or cells from immune-privileged sites, resist FasL⁺ T-cell-induced cell death. The mechanisms involved are a counterattack of immune cells by FasL, by releasing a soluble form of FasL that competes with the membrane version, and inhibits their cell death, promoting cell survival. This review focuses on understanding the previously unrecognized role of FasL, and in particular its soluble form, sFasL, in the serum of aged subjects, and its association with the evolution of lung disease, paving the way to new methods of diagnosis and treatment.