THE PERMEATION OF BIOMACROMOLECULES THROUGH HUMAN SKIN: AN INSIGHT INTO THE FAMILY OF GLYCOSAMINOGLYCANS

This Ph.D was aimed to elucidate the physicochemical parameters that rule the penetration of different classes of glycosaminoglycans (GAGs) through human skin, with particular focus on hyaluronan (HA) and heparins. The research activity involved: 1) the investigation of the influence of the main structural features (sequence, molecular weight (Mw), polarity, and conformational behavior) on the percutaneous absorption of HA, heparin (UFH) and low molecular weight heparins (LMWHs); 2) the fine-tuning of a suitable enhancement strategy to improve the permeation of UFH through human epidermis. The overall results confirmed that Mw represents a fundamental factor in determining the permeability properties also of such polysaccharides. Indeed, in in vitro studies performed by using HA having different chain lengths, the diffusion through the skin decreased increasing the polymer\u2019s molecular mass. Similarly, LMWHs sodium salts permeated to a larger extent with respect to UFH and their permeated amounts varied with Mw according to an exponential relationship. However, the key parameter driving the permeation of such macromolecules through the skin resulted to be the polymer flexibility. In fact, the introduction of sulfate groups on HA chains, causing the disruption of the helical motif, led to less ordered structures, which were able to cross the skin to higher extent compared to unsubstituted HA, despite their increased polarity. Accordingly, the presence of divalent cations in LMWHs solution, limiting the chain flexibility through the formation of intramolecular chelates, negatively affected the skin permeability properties of calcium nadroparin. Furthermore, both classes of polysaccharides in study demonstrated to interact with stratum corneum components, in particular keratins, as confirmed by confocal miscroscopy images (HA) and ATR-FTIR spectra (UFH). Since the physicochemical features of these polysaccharides (hydrophilicity, negative charge and high Mw) precluded a significant diffusion through the human epidermis, the phage display technique was exploited to screen a skin penetrating peptide which could enhance the skin permeation of such molecules, allowing their transdermal delivery. The in vitro screening allowed to identify a neutral peptide, DRTTLTN, which resulted to be able to increase the UFH flux of 34-fold after chemical conjugation. These results demonstrated the suitability of skin penetrating peptides to improve the skin delivery of polysaccharide macromolecules

New Sequential Methods for Detecting Portscanners

In this paper, we propose new sequential methods for detecting port-scan attackers which routinely perform random "portscans" of IP addresses to find vulnerable servers to compromise. In addition to rigorously control the probability of falsely implicating benign remote hosts as malicious, our method performs significantly faster than other current solutions. Moreover, our method guarantees that the maximum amount of observational time is bounded. In contrast to the previous most effective method, Threshold Random Walk Algorithm, which is explicit and analytical in nature, our proposed algorithm involve parameters to be determined by numerical methods. We have developed computational techniques such as iterative minimax optimization for quick determination of the parameters of the new detection algorithm. A framework of multi-valued decision for testing portscanners is also proposed.Comment: 11 pages, 5 figures, the mathematical theory of the detection algorithm has been presented in SPIE conference

Exact Methods for Multistage Estimation of a Binomial Proportion

We first review existing sequential methods for estimating a binomial proportion. Afterward, we propose a new family of group sequential sampling schemes for estimating a binomial proportion with prescribed margin of error and confidence level. In particular, we establish the uniform controllability of coverage probability and the asymptotic optimality for such a family of sampling schemes. Our theoretical results establish the possibility that the parameters of this family of sampling schemes can be determined so that the prescribed level of confidence is guaranteed with little waste of samples. Analytic bounds for the cumulative distribution functions and expectations of sample numbers are derived. Moreover, we discuss the inherent connection of various sampling schemes. Numerical issues are addressed for improving the accuracy and efficiency of computation. Computational experiments are conducted for comparing sampling schemes. Illustrative examples are given for applications in clinical trials.Comment: 38 pages, 9 figure

Square-free values of reducible polynomials

We calculate admissible values of r such that a square-free polynomial with integer coefficients, no fixed prime divisor and irreducible factors of degree at most 3 takes infinitely many values that are a product of at most r distinct primes.Comment: 18 pages; the new version of this article has been reformatted for Discrete Analysis but it is otherwise identical to the previous version, in Discrete Analysis 2016:

A glimpse in critical attributes to design cutaneous film forming systems based on ammonium methacrylate

A film forming system based on Eudragit\uae RL (EuRL) was designed aiming to evidence the relevance of formulative variables on the following critical attributes: film forming rate, outward stickiness, Young modulus (Y) and in vitro drug skin permeation. Different solvent mixtures (acetone and isopropanol in the range from 10:90 to 40:60 v/v), polymer concentrations (10-30 % w/w), and plasticizer types and concentrations (triacetin or tributyl citrate, up to 50% of EuRL) were evaluated. EuRL dissolved in 80/20 or 70/30 v/v isopropanol/acetone mixtures at the concentration of 20% and plasticized with tributyl citrate (20 or 30% with respect to polymer) gave films with negligible stickiness and Y lower than 3 MPa. This value should assure an intimate and prolonged contact with the skin since it was significantly lower than Y of human stratum corneum (55 MPa). The optimized formulations were able to sustain the skin permeation of ibubrofen, ketoprofen and flurbiprofen and evidenced the importance of each formulative variable. In particular, relatively slow solvent evaporation rate can determine an initial \u201cburst\u201d effect and can influence the drug permeation in the initial hours. Conversely, when the solvent evaporation rate is not discriminant, the thermodynamic activity remains the main parameter driving the skin permeation

Poly(methyl methacrylate) salt as film forming material to design orodispersible films

This work aims to evaluate the possible use of a poly(sodium methacrylate, methyl methacrylate) (NaPMM2) plasticized by PEG400 in design orodispersible films (ODF). Placebo ODF prepared by solvent casting were intended to study the impact of the polymer/plasticizer ratio and residual moisture on disintegration time, stickiness and mechanical properties. The drug loading capacity was assessed using ketoprofen and paracetamol. Placebo ODF containing PEG400 in the 10\u201330% w/w range and 10\u201315% of residual moisture content were easy-to-handle, packed without failures and completely dissolved within 30\u202fs. NaPMM2/PEG in 80/20 ratio allowed up to 70% of paracetamol loading, which appeared as the largest value described in literature. This ODF showed good mechanical properties and disintegration time. The same formulation loaded with 25% or 50% ketoprofen (pKa\u202f=\u202f4.45) swelled without disintegrating, because of a partial protonation of NaPPM2, as verified by ATR-FTIR spectroscopy. However, the addition of 5% surfactants allowed the formulation of ODF containing 25% ketoprofen that disintegrated within one minute and guaranteed the complete drug dissolution within 5\u202fmin. All the presented data, discussed in the framework of information available on such copolymer, highlighted its versatility in the design of orodispersible dosage forms

The manufacture and mechanical properties of a novel negative Poisson’s ratio 3-component composite

This paper was presented at the ICCM 20 Conference - 20th International Conference on Composite Materials in Copenhagen, 19-24 July 2015. Full conference proceedings are available via the link in this recordMaterials with a negative Poisson’s ratio known also as auxetic materials [1] exhibit unusual property of getting thicker when stretched and thinner when compressed. The helical auxetic yarn (HAY) is a recently invented auxetic reinforcing structure for composites [2]. A helical auxetic yarn (HAY) consists of two fibres: a low modulus elastomeric core and a high modulus wrap fibre in a double helix structure. When a tensile load is applied the core of the HAY becomes wider as the wrap straightens out, resulting in a lateral expansion of the core, and therefore a large negative Poisson’ ratio behaviour. The auxetic behaviour of the HAY can be tailored by altering fibre properties, the initial geometry and also the applied strain to comply with specific applications, such as composites [3, 4], blast mitigation, and filtration [5]. This paper introduces a further development to the current HAY by addition of a third component (a sheath). The presence of the sheath is expected to overcome problems such as slippage of the wrap and inconsistency in the initial wrap angle previously encountered during the manufacture of the HAY. The auxetic performance of conventional and novel systems is investigated and Poisson’s ratio data are presented.Engineering and Physical Sciences Research Council (EPSRC

The Actin Cortex: A Bridge between Cell Shape and Function

The cortical actin network controls many animal cell shape changes by locally modulating cortical tension. Recent work has provided insight into cortex components and regulators. However, how the network is reorganized in response to cellular signaling, and the role reorganization may play during cell state changes, remain to be determined