Effect of the Mechanical Properties of Soft Counter-Faces on the Adhesive Capacity of Mushroom-Shaped Biomimetic Microstructures.

The effects of mechanical properties and contact environment conditions on the adhesiveness of the biomimetic adhesive mushroom-shaped micro-structure have been experimentally investigated. The idea is based on the adhesive micro-structures and surfaces inspired by nature after observing the abilities of some animals. Applications are proposed in various fields of engineering and technology. However, to enable unconventional uses of these biomimetic adhesion surfaces, such as in the biomedical field, it is necessary to adjust and optimize their tribological properties (friction, adhesion, and peeling strength) in contact with soft substrates that can simulate the mechanical features of biological tissues. Our work explores the effect of the combinations of the various parameters on the strength of adhesion. Under dry contact conditions, soft counter-faces lead to lower adhesion than hard counter-faces, whereas under wet conditions, soft counter-faces lead to higher adhesion than harder counter-faces.

Intrinsically Disordered Synthetic Polymers in Biomedical Applications.

In biology and medicine, intrinsically disordered synthetic polymers bio-mimicking intrinsically disordered proteins, which lack stable three-dimensional structures, possess high structural/conformational flexibility. They are prone to self-organization and can be extremely useful in various biomedical applications. Among such applications, intrinsically disordered synthetic polymers can have potential usage in drug delivery, organ transplantation, artificial organ design, and immune compatibility. The designing of new syntheses and characterization mechanisms is currently required to provide the lacking intrinsically disordered synthetic polymers for biomedical applications bio-mimicked using intrinsically disordered proteins. Here, we present our strategies for designing intrinsically disordered synthetic polymers for biomedical applications based on bio-mimicking intrinsically disordered proteins.

Lumbosacral zone features in individuals with nonspecific chronic low back pain are unique compared to controls and correlate with pain and dysfunction.

OBJECTIVES: To compare the lumbosacral nerve distances (LNDs) and sacroiliac joint (SIJ) morphology in individuals with nonspecific chronic low back pain (NSCLBP) and control and examine their correlations with pain and dysfunction in the former. MATERIALS AND METHODS: The sample includes 200 adult patients (ranging from 20 to 50 years old) referred for computerized abdominal tomography (CT): 100 individuals with NSCLBP (50 males and 50 females) and 100 individuals without NSCLBP (50 males and 50 females). CT scans were assessed for LNDs, degenerative sacroiliac changes, and joint bridging. Those factors were correlated to the outcomes of three self-reported questionnaires about pain and function (Oswestry, Fear-Avoidance, and Numerical Pain Rating Scale) in the NSCLBP group. RESULTS: Individuals with NSCLBP tend to have reduced LNDs from the sacral part of the SIJ compared to controls (males: right Δ = 5.8 mm, left Δ = 6.03 mm; females: right Δ = 7.9 mm, left Δ = 7.73 mm, two-way ANOVA, p < 0.01), with moderate significant negative correlations with all three questionnaires (-0.38 < Pearson's r < - 0.57, p < 0.02, i.e., reduced LNDs with greater disability and pain). The NSCLBP group had more significant SIJ degeneration severity that moderately correlated with two questionnaires (0.39 < Pearson's r < 0.66, p < 0.04, i.e., greater SIJ degeneration with greater disability and pain). In males, the existence of SIJ bridging strongly correlated with all three questionnaires (0.38 < Pearson's r < 0.78, p < 0.03), and in females, only the Fear-Avoidance Questionnaire and Numerical Pain Scale (0.29 < Pearson's r < 0.41, p < 0.04). CONCLUSION: Compared to controls, individuals with NSCLBP have reduced LNDs and worse SIJ degenerative changes that correlate with function and pain. KEY POINTS: • Individuals with nonspecific low back pain tend to have reduced lumbosacral nerve distances than healthy controls. This may be due to entrapments or inflammation of the nerves or surrounding tissues. • Individuals with nonspecific low back pain tend to have more severe degeneration of their sacroiliac joint than healthy controls. • The above findings significantly correlated with the scores of three self-reported questionnaires about pain and function, implicating that they may be of clinical significance.

Preparation and characterization of flexible furosemide-loaded biodegradable microneedles for intradermal drug delivery.

Transdermal drug delivery systems are a useful and minimally invasive alternative to other drug administration routes. Biodegradable polymeric microneedles (MNs) are widely used in controlled-release drug delivery due to their tunable properties and ease of patient self-administration. Polylactic-co-glycolic acid (PLGA) is often used for sustained drug release owing to special intrinsic properties including biocompatibility and biodegradability, which offer excellent applicability in preparing MNs. Congestive heart failure (CHF) is characterized by fluid overload during acute exacerbation, necessitating frequent patient hospitalization for continuous intravenous (i.v.) diuretic therapy. In the present study, we incorporated furosemide (FUR) as a model drug into flexible PLGA MN skin patches for potential intradermal delivery to overcome the limitations associated with i.v. diuresis. The MNs were fabricated by a casting-mold technique and consisted of two main parts, PLGA needle tips loaded with varying concentrations of FUR and a flexible backing layer comprising sodium alginate and glycerol. MN formulations were characterized by SEM and exhibited a uniform pyramidal shape. The measured surface pH of all samples suggested that no skin irritation is expected upon application. High encapsulation efficiency was obtained for FUR-MN formulations in which a decrease was noted as the FUR/PLGA ratio decreased. Drug loading content ranged from 19.1 ± 1% to 28.9 ± 1.4%. Successful insertion of MNs into a Parafilm® skin simulant model suggested that MNs will easily penetrate the skin's outermost layer, the stratum corneum, and will permit intradermal delivery of FUR. The MNs were further characterized by analytical methods. Finally, the MNs exhibited an initial burst release followed by a sustained release of FUR. Self-administered FUR-MNs can open new avenues to overcome i.v. drip limitations and increase patient compliance.

Biomimetic clotrimazole-loaded PLGA films with enhanced adhesiveness for controlled drug release.

Biomimetic adhesive surfaces have a number of potential applications in the pharmaceutical and biomedical fields. Fabrication techniques must be adapted to biocompatible and biodegradable materials required for controlled drug release applications. In this study biomimetic adhesive poly(lactic-co-glycolic acid) (PLGA) films loaded with different concentrations of clotrimazole (CTZ) were prepared without combining other adhesive excipients as a controlled release system for potential local oral drug delivery. The films were fully characterized from morphological point of view, and CTZ-loaded biomimetic films exhibited adequate surface pH values, high drug encapsulation efficiency, and loading content. The adhesion strength of the obtained films was significantly higher compared to a flat film reference under different contact conditions. Thermal analysis indicated a decrease of drug crystallinity upon incorporation into PLGA films. The in vitro release of CTZ from PLGA biomimetic films was tested in simulated saliva, and it exhibited an initial burst release, accompanied by a sustained release phase over 10 days. Finally, the mucoadhesive properties of the obtained films was studied using agar/mucin plate as a representative mucosal substrate, and the results demonstrated superior mucoadhesion potential of CTZ-loaded biomimetic film in comparison to its flat counterpart. Having demonstrated the ability to load CTZ into PLGA biomimetic films with enhanced adhesion capacity, the potential use in local oral drug delivery applications warrants further in vitro and in vivo investigations.

Effect of counterface roughness on the friction of bionic wall-shaped microstructures for gecko-like attachments.

Hairy adhesive systems involved in gecko locomotion have drawn the interest of many researchers regarding the development of bionic solutions for fast and reversible adhesive technologies. To date, despite extensive efforts to design gecko-inspired adhesive surfaces, adhesion and friction capacities are often evaluated using smooth and rigid counterfaces, in general glass, whereas most natural and artificial surfaces inevitably have a certain level of roughness. For that reason, in this study experiments tested the effects of the substrate roughness on the friction of bionic wale-shaped microstructures for gecko-like attachments. To this end, 12 substrates with different isotropic roughness were prepared using the same Epoxy material. Friction force was measured under various normal loads. It was concluded that classical roughness parameters, considered separately, are not appropriate to explain roughness-related variations in friction force. This has led us to develop a new integrative roughness parameter that combines characteristics of the surface. The parameter is capable of classifying the obtained experimental results in a readable way. An analytical model based on the experimental results has been developed to predict the variation of the friction force as a function of counterface roughness and applied normal load.

Biomimetic wall-shaped hierarchical microstructure for gecko-like attachment.

Most biological hairy adhesive systems involved in locomotion rely on spatula-shaped terminal elements, whose operation has been actively studied during the last decade. However, though functional principles underlying their amazing performance are now well understood, due to technical difficulties in manufacturing the complex structure of hierarchical spatulate systems, a biomimetic surface structure featuring true shear-induced dynamic attachment still remains elusive. To try bridging this gap, a novel method of manufacturing gecko-like attachment surfaces is devised based on a laser-micromachining technology. This method overcomes the inherent disadvantages of photolithography techniques and opens wide perspectives for future production of gecko-like attachment systems. Advanced smart-performance surfaces featuring thin-film-based hierarchical shear-activated elements are fabricated and found capable of generating friction force of several tens of times the contact load, which makes a significant step forward towards a true gecko-like adhesive.

Effect of counterface roughness on adhesion of mushroom-shaped microstructure.

In this study, the effect of the substrate roughness on adhesion of mushroom-shaped microstructure was experimentally investigated. To do so, 12 substrates having different isotropic roughness were prepared from the same material by replicating topography of different surfaces. The pull-off forces generated by mushroom-shaped microstructure in contact with the tested substrates were measured and compared with the pull-off forces generated by a smooth reference. It was found that classical roughness parameters, such as average roughness (Ra) and others, cannot be used to explain topography-related variation in pull-off force. This has led us to the development of an integrated roughness parameter capable of explaining results of pull-off measurements. Using this parameter, we have also found that there is a critical roughness, above which neither smooth nor microstructured surface could generate any attachment force, which may have important implications on design of both adhesive and anti-adhesive surfaces.