Development of a Fully Synthetic Corneal Stromal Construct via Supramolecular Hydrogel Engineering

Recent advances in the field of ophthalmology show great potential in the design of bioengineered constructs to mimic the corneal stroma. Hydrogels based on synthetic supramolecular polymers, are attractive synthetic mimics of the natural highly hydrated corneal stroma. Here, a fully synthetic corneal stromal construct is developed via engineering of an injectable supramolecular hydrogel based on ureido-pyrimidinone (UPy) moieties. The hydrogel displays a dynamic and tunable behavior, which allows for control of biochemical and mechanical cues. Two hydrogels are developed, a fully synthetic hydrogel functionalized with a bioactive cyclic arginine-glycine-aspartate UPy (UPy-cRGD) additive, and a hybrid hydrogel based on UPy-moieties mixed with collagen type I fibers. Both hydrogels supported cell encapsulation and associated cellular deposition of extracellular matrix (ECM) proteins after 21 days. Excitingly, the hydrogels support the activation of isolated primary keratocytes into stromal fibroblasts as well as the differentiation toward more quiescent corneal stromal keratocytes, demonstrated by their characteristic long dendritic protrusions and a substantially diminished cytokine secretion. Furthermore, cells survive shear stresses during an injectability test. Together, these findings highlight the development of an injectable supramolecular hydrogel as a synthetic corneal stromal microenvironment able to host primary keratocytes.</p

Enhanced Secrecy in Optical Communication using Speckle from Multiple Scattering Layers

We study the secrecy of an optical communication system with two scattering layers, to hide both the sender and receiver, by measuring the correlation of the intermediate speckle generated between the two layers. The binary message is modulated as spatially shaped wavefronts, and the high number of transmission modes of the scattering layers allows for many uncorrelated incident wavefronts to send the same message, making it difficult for an attacker to intercept or decode the message and thus increasing secrecy. We collect 50,000 intermediate speckle patterns and analyze their correlation distribution using Kolmogorov-Smirnov (K-S) test. We search for further correlations using the K-Means and Hierarchical unsupervised classification algorithms. We find no correlation between the intermediate speckle and the message, suggesting a person-in-the-middle attack is not possible. This method is compatible with any digital encryption method and is applicable for codifications in optical wireless communication (OWC)

Theoretical Study of Fast Light with Short sech Pulses in Coherent Gain Media

We investigate theoretically the phenomenon of so-called fast light in an unconventional regime, using pulses sufficiently short that relaxation effects in a gain medium can be ignored completely. We show that previously recognized gain instabilities, including superfluorescence, can be tolerated in achieving a pulse peak advance of one full peak width.Comment: 7 pages, 8 figures; Replaced with revised version accepted by JOSA

Development of an Antimicrobial Peptide SAAP-148-Functionalized Supramolecular Coating on Titanium to Prevent Biomaterial-Associated Infections

Titanium implants are widely used in medicine but have a risk of biomaterial-associated infection (BAI), of which traditional antibiotic-based treatment is affected by resistance. Antimicrobial peptides (AMPs) are used to successfully kill antibiotic-resistant bacteria. Herein, a supramolecular coating for titanium implants is developed which presents the synthetic antimicrobial and antibiofilm peptide SAAP-148 via supramolecular interactions using ureido-pyrimidinone supramolecular units (UPy-SAAP-148GG). Material characterization of dropcast coatings shows the presence of UPy-SAAP-148GG at the surface. The supramolecular immobilized peptide remains antimicrobially active in dropcast polymer films and can successfully kill (antibiotic-resistant) Staphylococcus aureus, Acinetobacter baumannii, and Escherichia coli. Minor toxicity for human dermal fibroblasts is observed, with a reduced cell attachment after 24 h. Subsequently, a dipcoat coating on titanium implants is developed and tested in vivo in a subcutaneous implant infection mouse model with S. aureus administered locally on the implant before implantation to mimic contamination during surgery. The supramolecular coating containing 5 mol% of UPy-SAAP-148GG significantly prevents colonization of the implant surface as well as of the surrounding tissue, with no signs of toxicity. This shows that supramolecular AMP coatings on titanium are eminently suitable to prevent BAI.</p

Spinor condensates and light scattering from Bose-Einstein condensates

These notes discuss two aspects of the physics of atomic Bose-Einstein condensates: optical properties and spinor condensates. The first topic includes light scattering experiments which probe the excitations of a condensate in both the free-particle and phonon regime. At higher light intensity, a new form of superradiance and phase-coherent matter wave amplification were observed. We also discuss properties of spinor condensates and describe studies of ground--state spin domain structures and dynamical studies which revealed metastable excited states and quantum tunneling.Comment: 58 pages, 33 figures, to appear in Proceedings of Les Houches 1999 Summer School, Session LXXI