Andrea Merlettini

Thixotropic Peptide-Based Physical Hydrogels Applied to Three-Dimensional Cell Culture

Pseudopeptides containing the d-Oxd or the d-pGlu [Oxd = (4R,5S)-4-methyl-5-carboxyl-oxazolidin-2-one, pGlu = pyroglutamic acid] moiety and selected amino acids were used as low-molecular-weight gelators to prepare strong and thixotropic hydrogels at physiological pH. The addition of calcium chloride to the gelator solutions induces the formation of insoluble salts that get organized in fibers at a pH close to the physiological one. Physical characterization of hydrogels was carried out by morphologic evaluation and rheological measurements and demonstrated that the analyzed hydrogels are thixotropic, as they have the capability to recover their gel-like behavior. As these hydrogels are easily injectable and may be used for regenerative medicine, they were biologically assessed by cell seeding and viability tests. Human gingival fibroblasts were embedded in 2% hydrogels; all of the hydrogels allow the growth of encapsulated cells with a very good viability. The gelator toxicity may be correlated with their tendency to self-assemble and is totally absent when the hydrogel is formed.

Pseudopeptide‐Based Hydrogels Trapping Methylene Blue and Eosin Y

We present herein the preparation of four different hydrogels based on the pseudopeptide gelator Fmoc-l-Phe-d-Oxd-OH (Fmoc=fluorenylmethyloxycarbonyl), either by changing the gelator concentration or adding graphene oxide (GO) to the water solution. The hydrogels have been analysed by rheological studies that demonstrated that pure hydrogels are slightly stronger compared to GO-loaded hydrogels. Then the hydrogels efficiency to trap the cationic methylene blue (MB) and anionic eosin Y (EY) dyes has been analyzed. MB is efficiently trapped by both the pure hydrogel and the GO-loaded hydrogel through π-π interactions and electrostatic interactions. In contrast, the removal of the anionic EY is achieved in less satisfactory yields, due to the unfavourable electrostatic interactions between the dye, the gelator and GO.

Self-healing hydrogels triggered by amino acids

Nine amino acids with different chemical properties have been chosen to promote the formation of hydrogels based on the bolamphiphilic gelator A: three basic amino acids (arginine, histidine and lysine), one acidic amino acid (aspartic acid), two neutral aliphatic amino acids (alanine and serine) and three neutral aromatic amino acids (phenylalanine, tyrosine and tryptophan). Although hydrogels are obtained under any conditions, strong and thermoreversible hydrogels are formed by the addition of Arg to the bolamphiphilic gelator. These hydrogels have physiological pH and self-healing properties and may be used for regenerative medicine applications.

Facile fabrication of shape memory poly(ε-caprolactone) non-woven mat by combining electrospinning and sol–gel reaction

Poly(e-caprolactone)-based non-woven fibrous mats showing excellent one-way shape memory properties were obtained through a straightforward approach by combining electrospinning process and sol–gel reaction. A solution of partially crosslinked α,ω-triethoxysilane-terminated poly(e-caprolactone) was used to obtain bead-free fibers through electrospinning. Non-woven mats with different crosslinking degrees have been prepared and the effect of the different crosslinking extent and of the microfibrous structure were correlated to the mechanical and shape memory properties of the material. The evolution of fiber architecture within the non-woven mat following deformation and shape memory cycles was also investigated.

Antibody immobilization on poly(L-lactic acid) nanofibers advantageously carried out by means of a non-equilibrium atmospheric plasma process

In the present study, the comparison between a conventional wet-chemical method and a non-equilibrium atmospheric pressure plasma process for the conjugation of biomolecules on the surface of poly(L-lactic acid) (PLLA) electrospun fibers is reported. Physico-chemical and morphological characteristics of chemically and plasma functionalized mats are studied and compared with those of pristine mats. The efficiency in biomolecules immobilization is assessed by the covalent conjugation of an antibody (anti-CD10) on the functionalized PLLA fibers. The achieved results highlight that the proposed plasma process enables antibodies to be successfully immobilized on the surface of PLLA fibers, demonstrating that non-equilibrium atmospheric pressure plasma can be an effective, highly flexible and environmentally friendly alternative to the still widely employed wet-chemical methods for the conjugation of biomolecules onto biomaterials.

Two-Way Shape Memory Behavior of Electrospun Non-Woven Mats Prepared from Sol-Gel Crosslinked Poly(ε-Caprolactone)

Non-woven fibrous mats based on semicrystalline networks were prepared starting from poly(ε-caprolactone) and by combining electrospinning process and sol-gel crosslinking reaction. The mats were subjected to proper thermo-mechanical cycles to investigate their two-way shape memory capabilities (i.e. the possibility to change between two distinguished shapes upon heating and cooling), and an improvement of the two-way behaviour was researched through the application of a training cycle. An ex-situ SEM analysis described the microstructural evolution accompanying the two-way shape memory cyclic response.

Advances in multidrug delivery from electrospun nanomaterials

Abstract Multidrug delivery systems are attracting increasing interest nowadays given their great potential as a novel therapeutic combination for different diseases, including cancer. Many different approaches have been explored to create a library of multidrug systems with controlled release kinetics, able to fulfill most medical demands. In this context electrospinning, due to its versatility, represents a valuable technique to load multiple active agents into polymeric nano–microfibers. A broad range of synthetic and natural polymers can be processed into electrospun fibers, allowing the development of drug delivery systems with a broad spectrum of different chemical and physical properties. In this chapter three main methods, (1) monolithic electrospun fibers, (2) core-sheath fibers, and (3) electrospun fibers loaded with nanocarriers, will be discussed in detail, underlining the pros and cons of each technique and discussing the most representative examples reported in literature.

Shape memory electrospun nonwovens based on crosslinked poly(ε-caprolactone) for multifunctional biological applications

In this work we have explored the capabilities of an electrospun mat, realized in crosslinked poly(e-caprolactone), to be employed as a scaffold for specific biological applications. Its shape memory behavior was here exploited to easily control fiber orientation and to guide cellular alignment. Randomly oriented mats were transformed in a stable shape with various degrees of fiber alignment by simply varying the maximum strain applied throughout proper thermo-mechanical cycles. The effect of fiber alignment was investigated both on mechanical properties and on cell culture, through biological characterization done by using Neural Stem Cells derived from human iPSCs (induced Pluripotent Stem Cells). Further, thanks to the thermal stability of the microfibrous structure, it was possible to transfer, through inkjet printing on the electrospun, a biocompatible sensing element, which successfully allowed to monitor cell adhesion (L6 Myoblast) in an innovative way under dynamic conditions.In this work we have explored the capabilities of an electrospun mat, realized in crosslinked poly(e-caprolactone), to be employed as a scaffold for specific biological applications. Its shape memory behavior was here exploited to easily control fiber orientation and to guide cellular alignment. Randomly oriented mats were transformed in a stable shape with various degrees of fiber alignment by simply varying the maximum strain applied throughout proper thermo-mechanical cycles. The effect of fiber alignment was investigated both on mechanical properties and on cell culture, through biological characterization done by using Neural Stem Cells derived from human iPSCs (induced Pluripotent Stem Cells). Further, thanks to the thermal stability of the microfibrous structure, it was possible to transfer, through inkjet printing on the electrospun, a biocompatible sensing element, which successfully allowed to monitor cell adhesion (L6 Myoblast) in an innovative way under dynamic conditions.

Carbon on poly(ε-caprolactone) (PCL) Ink-jet Printed Sensor for Monitoring Cell Cultures of Myoblasts

Nowadays techniques for sensitive non-invasive, real-time monitoring of cell differentiation and maturation are highly demanded. In light of this, the development of electrochemical printed sensors impedance-based could represent a promising tool. In the present work, we developed 2D ink-jet printed sensors for myoblasts adhesion monitoring, using carbon-based ink on a substrate consisting in non-woven electrospun mats made in crosslinked poly(e-caprolactone) (PCL). First of all, sensors printability was optimized and the biocompatibility tested. In order to determine the possibility to employ the prepared systems as scaffolds for dynamic cellular cultures, the mechanical response of the PCL scaffold was evaluated through the application of cyclic deformation tests. After that, electrical characterization of ink and substrate was performed, followed by electrochemical impedance-based measurements to evaluate myoblasts adhesion. Biocompatibility assessment showed good results for both carbon and PCL. Mechanical tests findings suggested that a training of 50 cycles and a proper value of strain should be applied before the cell seeding, in order to ensure a subsequent controlled strain amplitude. The sensorized scaffold allowed us to correlate cell adhesion with an increase of impedance module, in agreement with biocompatibility testing. Thus, this first preliminary testing suggested that this non-invasive impedance spectroscopy-based measurement system can be used for sensitive monitoring of cells adhesion, in static and moreover, as suggested from mechanical characterization, in dynamic conditions.