Microgel-based surface modifying system for stimuli-responsive functional finishing of cotton

An innovative strategy for functional finishing of textile materials is based on the incorporation of a thin layer of surface modifying systems (SMS) in the form of stimuli-sensitive microgels or hydrogels. Since the copolymerization of poly(N-isopropylacrylamide) with an ionizable polymer, such as chitosan, results in a microgel that is responsive to both temperature and pH, the microparticulate hydrogel of poly-NiPAAmchitosan copolymer (PNCS) was synthesized using surfactant-free emulsion method. The microparticle size in dry (collapsed) state is estimated at 200nm by SEM and TEM, and effect of temperature and pH on microparticles was investigated by DLS and UV–vis spectrophotometry. The incorporation of PNCS microparticles to cotton material was done by a simple pad-dry-cure procedure from aqueous microparticle dispersion that contained 1,2,3,4-butanetetracarboxylic acid (BTCA) as a crosslinking agent. This application method provided sufficient integrity to coating by maintaining the responsiveness of surface modifying system. The stimuli-responsiveness of modified cotton fabric has been confirmed in terms of regulating its water uptake in dependence of pH and temperature

Thermosensitive PNIPAM grafted alginate/chitosan PEC

Smart biomaterial functionality such as controlled adhesion properties is crucial to limit strip-off injuries. Among functional polymers, poly-N(isopropylacrylamide) (PNIPAM) allows surface properties to be changed depending on the temperature, with a transition of its properties that occurs around 32 °C, called the lower critical solution temperature (LCST). This transition is expected to modify surface interactions. Alginate and chitosan are biocompatible polymers commonly combined as polyelectrolyte complex (PEC) and are suitable for wound dressing applications. As a complex system, however, it is not so trivial to achieve an efficient functionalization. Herein, we elaborated a procedure to functionalize the surface of alginate/chitosan PECs without altering their intrinsic properties. FTIR revealed that acidic treatment led to a partial decomplexation of the PECs. Therefore, while the N-Hydroxysuccinimide/N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide (NHS/EDC) coupling usually requires an intermediate pH, we showed that a preliminary acidification seemed to increase the surface grafting efficiency. Water contact angle increased from 51° to 72°, showing that PNIPAM enhanced the surface hydrophobicity. The LCST transition modified the interaction forces between PNIPAM and model surfaces: it revealed an unexpected thermosensitive behaviour as hydrophobic transition favoured interactions with hydrophilic surfaces. It was presumably due to PNIPAM/PEC substrate interactions. Finally, the surface modification did not affect the release properties of the PEC biomaterial

Attachment of β-Cyclodextrins on Cotton and Influence of β-Cyclodextrin on Ester Formation with BTCA on Cotton

Cotton was treated with β-cyclodextrin (BCD) and two derivatives of β-cyclodextrin (2-hydroxypropyl-β-cyclodextrin and monochlorotriazinyl-B-cyclodextrin) to assess the optimal type for fixation with cotton. The experimental results showed that treatment of cotton with BCD using the crosslinker BTCA resulted in higher fixation than the treatments with the other two derivatives. The concentration of BTCA used did not significantly influuence the amount of fixation of BCD on cotton. FTIR-ATR spectroscopic analysis showed that the amount of ester formed on the fabric was influenced by the addition of BCD on cotton with BTCA in comparison to crosslinking of only BTCA with cotton. The laundering tests showed relatively poor washfastness of the β-cyclodextrins on the fabrics

Adsorption of nucleotides on biomimetic apatite: the case of cytidine 5′ monophosphate (CMP)

The chemical interaction between DNA macromolecules and hard tissues in vertebrate is of foremost importance in paleogenetics, as bones and teeth represent a major substrate for the genetic material after cell death. Recently, the empirical hypothesis of DNA ‘‘protection’’ over time thanks to its adsorption on hard tissues was revisited from a physico-chemical viewpoint. In particular, the existence of a strong interaction between phosphate groups of DNA backbone and the surface of apatite nanocrystals (mimicking bone/dentin mineral) was evidenced on an experimental basis. In the field of nanomedicine, DNA or RNA can be used for gene transport into cells, and apatite nanocarriers then appear promising. In order to shed some more light on interactions between DNA molecules and apatite, the present study focuses on the adsorption of a ‘‘model’’ nucleotide, cytidine 50 monophosphate (CMP), on a carbonated biomimetic apatite sample. The follow-up of CMP kinetics of adsorption pointed out the rapidity of interaction with stabilization reached within few minutes. The adsorption isotherm could be realistically fitted to the Sips model (Langmuir–Freundlich) suggesting the influence of surface heterogeneities and adsorption cooperativity in the adsorption process. The desorption study pointed out the reversible character of CMP adsorption on biomimetic apatite. This contribution is intended to prove helpful in view of better apprehending the molecular interaction of DNA fragments and apatite compounds, independently of the application domain, such as bone diagenesis or nanomedicine. This study may also appear informative for researchers interested in the origins of life on Earth and the occurrence and behavior of primitive biomolecules

Nitrogen sorption as a tool for the characterisation of polysaccharide aerogels

Supercritically dried aerogels of several polysaccharides (chitin, chitosan, alginate, alginic acid, k- carrageenan, and agar) have been characterised by physisorption ofN2. Surface areas as high as 570m2 g−1 have been measured. The nature of the functional groups of the polysaccharide significantly influences the adsorption of N2 on the surface of the aerogel. The net enthalpy of adsorption increases with the polarity of the surface groups of the polymer, in the order chitin < agar≤chitosan < carrageenan < alginic acid∼alginate. The surface area and the mesopore distribution of the aerogels depend both on the dispersion of the parent hydrogel and on the behaviour of each polymer in the drying treatment. Aerogels which retain the dispersion of the parent hydrogel are mainly macroporous (pores larger than 50 nm) while materials liable to shrink upon solvent exchange form mesoporous structures

PNIPAM grafted surfaces through ATRP and RAFT polymerization: Chemistry and bioadhesion

Biomaterials surface design is critical for the control of materials and biological system interactions.Being regulated by a layer of molecular dimensions, bioadhesion could be effectively tailored by polymersurface grafting. Basically, this surface modification can be controlled by radical polymerization, whichis a useful tool for this purpose. The aim of this review is to provide a comprehensive overview of therole of surface characteristics on bioadhesion properties. We place a particular focus on biomaterialsfunctionalized with a brush surface, on presentation of grafting techniques for “grafting to” and “graft-ing from” strategies and on brush characterization methods. Since atom transfer radical polymerization(ATRP) and reversible addition-fragmentation chain transfer (RAFT) polymerization are the most fre-quently used grafting techniques, their main characteristics will be explained. Through the example ofpoly(N-isopropylacrylamide) (PNIPAM) which is a widely used polymer allowing tuneable cell adhesion,smart surfaces involving PNIPAM will be presented with their main modern applications

Nanomedicine: Interaction of biomimetic apatite colloidal nanoparticles with human blood components

This contribution investigates the interaction of two types of biomimetic-apatite colloidal nanoparticles (negatively-charged 47nm, and positively-charged 190nm NPs) with blood components, namely red blood cells (RBC) and plasma proteins, with the view to inspect their hemocompatibility. The NPs, preliminarily characterized by XRD, FTIR and DLS, showed low hemolysis ratio (typically lower than 5%) illustrating the high compatibility of such NPs with respect to RBC, even at high concentration (up to 10mg/ml). The presence of glucose as water-soluble matrix for freeze-dried and re-dispersed colloids led to slightly increased hemolysis as compared to glucose-free formulations. NPs/plasma protein interaction was then followed, via non-specific protein fluorescence quenching assays, by contact with whole human blood plasma. The amount of plasma proteins in interaction with the NPs was evaluated experimentally, and the data were fitted with the Hill plot and Stern-Volmer models. In all cases, binding constants of the order of 101–102 were found. These values, significantly lower than those reported for other types of nanoparticles or molecular interactions, illustrate the fairly inert character of these colloidal NPs with respect to plasma proteins, which is desirable for circulating injectable suspensions. Results were discussed in relation with particle surface charge and mean particle hydrodynamic diameter (HD). On the basis of these hemocompatibility data, this study significantly complements previous results relative to the development and nontoxicity of biomimetic-apatite-based colloids stabilized by non-drug biocompatible organic molecules, intended for use in nanomedicine

Elaboration of a thermosensitive smart biomaterial: From synthesis to the ex vivo bioadhesion evaluation

Alginate and chitosan are polysaccharides that are widely used in the biomedical field, especially as wound dressings. Controlled bioadhesion is an advanced functionality that offers the potential to reduce injuries due to the stripping-off of the biomaterial. Herein, we report the efficient grafting of poly-N(isopropylacryamide) (PNIPAM), a thermosensitive polymer that exhibits a lower critical solution temperature (LCST) at 32 °C on the alginate/chitosan polyelectrolyte complex (PEC) surface. In vitro studies did not exhibit a cytotoxic effect, and cells adhered preferentially on the LCST on PNIPAM grafted surfaces, as reported in the literature. Ex vivo investigations revealed that the adhesive behavior of the biomaterials was not the same on the liver and pancreas. The effect of the temperature on the bioadhesion to organs was unexpected, as PNIPAM surfaces exhibited higher adhesion at low temperature. The PNIPAM was therefore able to confer PEC matrix thermosensitivity, but due to the application force, interactions between PNIPAM chains and their substrate could influence bioadhesion on tissues

Development and Characterization of Novel Bigel-Based 1,4-Naphthoquinones for Topical Application with Antioxidant Potential

Discovering new antioxidant agents and optimizing their processing is a necessity to treat skin diseases. The assessment of quality and antioxidant activity of topical formulations based on 5,8-dihydroxy-1,4-naphthoquinone (M1) and 2,3-dichloro-5,8-dihydroxy-1,4-naphthoquinone (M2) was carried out for the first time for this purpose. Stability studies including evaluation of pH, viscosity, microscopic observation, and microbiological quality were determined. M1 and M2 were examined for their antioxidant capacities after their incorporation into bigels. Obtained data suggested that BG-M1 and BG-M2 have a good quality, a natural pH of the skin (4.5–6.0), and no sign of microbial development. Sensory analysis was also performed, and no negative assessment of unpleasant bigel properties was found. M1 and M2 have shown antioxidant activity toward DPPH radical (data are expressed as IC50), 19 × 10−3 mg/mL for M1 and 35 × 10−3 mg/mL for M2, respectively. After their formulations, they have maintained this ability, for BG-M1 = 3.0 and BG-M2 = 1.1 mg/mL. Also, they demonstrated interesting ABTS scavenging with 1.5 × 10−3 and 2.5 × 10−3 mg/mL for M1 and M2, respectively. They kept this potential after formulation, since, BG-M1 = 1.7 mg/mL and BG-M2 = 4.9 mg/mL. Likewise, pure molecules revealed notable β-carotene bleaching inhibition (0.3 and 0.1 mg/mL for M1 and M2, respectively), which was maintained after their formulation into bigels (2.9 and 10.3 mg/mL for BG-M1 and BG-M2, respectively). These developed bigels maintaining the antioxidant potential of M1 and M2 could be used as the provision of a barrier to protect skin

Bio-inspired apatite particles limit skin penetration of drugs for dermatology applications

Most treatments of skin pathologies involve local administration of active agents. One issue can however be the partial transcutaneous diffusion of the drug to blood circulation, leading to undesirable effects. In this work, the original use of submicron mineral particles based on bio-inspired calcium phosphate apatite was explored for the first time as drug carriers for favoring topical delivery. The permeation of a model drug across synthetic and biological membranes was investigated in both static and dynamic conditions. Our data show that adsorption of the drug on the apatite particles surface drastically limits its permeation, with lower effective diffusion coefficients (Peff) and smaller total released amounts. The retention of the apatite colloidal particles on porcine ear skin explants surface was demonstrated by combining histological observations and Raman confocal microscopy. All results converge to show that association of the drug to apatite particles favors skin surface effects. These findings point to the relevance of mineral-based particles as drug carriers for local delivery to the skin, and open the way to novel applications of bio-inspired apatites in dermatology. Statement of Significance Calcium phosphates (CaP) are major biomaterials in orthopedics and dentistry. Their resemblance to bone mineral allows new applications beyond bone repair, e.g. in nanomedicine. In 2018, a 14-page detailed review (M. Epple, Acta Biomaterialia 77 (2018) 1–14) provided clear facts in favor of the non-toxicity of nanosized CaP as an answer to discussions from EU and US study groups, thus clarifying the path to novel applications of nano CaP. In the present paper, bio-inspired apatite nanoparticles are used for the first time as drug carriers for dermatology for drastically limiting drug transcutaneous permeation and retaining a topical effect. We demonstrate this proof of concept via permeation cell tests, histology, Raman microscopy and photoluminescence after application on porcine ear skin