Brief descriptions of the principles of prominent methods used to study the penetration of materials into human hair and a review of examples of their use

Consumers are attracted to the latest fashion trends and different looks. This drives search for novel hair treatments. Some chemicals present in treatment products can penetrate shaft. These materials either nourish or injure cortex. Different techniques have been used investigate mechanism of molecule penetration conditions under which occurs. article reviews applied this purpose. Various microscopy capture clear colourful images determine diffusion pathways exact location molecules study. However, laborious sample preparation often leads destruction since cross-sectioning is required. While various other successfully investigating methods, most these require amounts work be put instrumentation. Several spectroscopic study because high levels accuracy quick response time techniques. Moreover, samples not damaged during investigation. Les consommateurs sont attirés par les dernières tendances et différents styles de la mode. Cela stimule recherche pour nouveaux traitements capillaires. Certains produits chimiques présents dans soins capillaires peuvent pénétrer tige du cheveu. Ils tantôt nourrir, endommager le cortex pileux. Différentes ont été utilisées étudier mécanisme pénétration des molécules lesquelles cette a lieu. Cet examine appliquées à fin. Diverses microscopie mises en œuvre capturer claires colorées afin déterminer voies localisation exacte l’étude. Cependant, préparation laborieuse échantillons conduit fréquemment échantillons, car une coupe transversale est souvent exigée. Si plusieurs autres avec succès méthodes pénétration, plupart d’entre elles nécessitent niveaux d’activité mettre l’instrumentation. Plusieurs spectroscopiques raison leurs élevés précision leur délai réponse rapide. De plus, ne pas endommagés pendant l’investigation. Hair fibre may regarded as simple fragile. Over past years, scientists morphologies functions each component fibres detail. The cuticle, medulla form three major structural components hair. cuticle forms outermost part shaft has laminar structure. It protects inner structure from heat mechanical abrasion [1]. Each cuticular cell scale. layer covered with lipids (e.g. 18-methyleicosanoic acid, 18-MEA). highly resistant region against chemical aggression lower molecular organization than [2]. underneath scales constitutes approximately 70% 90% total mass. composed cellular structures an intercellular matrix. Cortical cells macrofibrils, formed smaller protein filaments known microfibrils. matrix rich keratin-associated proteins and/or intermediate filament-associated proteins. maximum amount disulphide bonds here [2, 3]. long, cylindrical lean located central fibre. small bags where fragments found membrane complex cementing function responsible maintenance allows into through route (the important pathway movement substances). Materials also get transported via less likely transcellular [4]. consists crosslinked regions, while densely well zones. size, solvent, temperature, pH condition material transport Organic (of varying sizes polarities) prefer migration, hydrophilic species migrate by current promotes development new some promise deep fibres. entry low-molecular-weight surfactants shampoos enter disturb hydrogen salt linkages [5]. Chemicals (which alter shape colour fibres) bleaching, perming, straightening dying reach cause significant damage [6-8]. Disulphide bonds, maintaining integrity, when broken, increase hydrophilicity fibres, leading higher rates swelling. causes increased [7, 9]. Cationic compounds, main conditioner formulations, protect fatigue stress. They enhance moisture retention ability [10]. Saturated monounsaturated oils prevent water ingress, consequently reducing swelling [11]. Other ingredients formulations (such proteins) potentially provide moistness deliver good finish [12]. become topic interest many scientists. mode Conditions such occurs investigated. optical microscopy, fluorescence electronic microscopy), spectroscopy spectrometry (spectrophotometry; microspectrophotometry: optical, fluorescence, ultraviolet spectroscopy; infrared (FTIR-AT); Raman secondary ion mass (SIMS): nanoscale time-of-flight (TOF-SIMS); spectrometry), radiolabelling, chromatography extraction methods. review aims visit studying penetration, discuss advantages disadvantages method point out relevant understanding science Microscopes became widely available 1800 s aided scientific discoveries (by allowing observation structures, physiology, functional parts objects) [13]. types modern microscopes developed over years [14]. field elucidate associated phenomena materials) methods visualization probe nondestructive way [15]. Microscopy ascertain compound that penetrated (before after exposure). extent diffusion. analyse damage. substances, using techniques, involves tracking dyes. A literature survey reveals fluorescent dyes (or compounds linked compounds), visible naked eyes, UV (present hair) identified reactions electron technique) studies. Apart molecules, procedure fixation (in resins glycerol) cutting optimal temperature. Optical technique amplifying objects samples. field. relies on concept light diffraction (adjusted system lenses) dark chamber size amplification [16]. utilizes (and/or pigments do excitation visualization) producing magnified orange II (acid dye) dye was keratin at low temperatures. compare two coloration involved use polyethylenimine (PEI) solution, counter reagent, presence absence urea. Urea behaved enhancer resulting deeper faster PEI penetration. exerted ionization II, enhanced [17]. In irradiated short wavelength light. emits portion absorbed (longer light) [18]. requires (an isolated interest). After preparation, parameters instrument set absorption emission wavelengths dye. around depth cross-sectional Fluorescence permeation synthetic peptides having 17 amino acids each. effects bleaching were investigated microscopy. covalently 5(6)-TAMRA (5(6)-carboxytetramethylrhodamine, succinimidyl ester) N-terminus. Silva, Vasconcelos [12] reported oxidation surface negatively charged. Peptide primarily due electrostatic complementarity. Thus, charge density extremely parameter determines peptide An alternative over-bleached (5(6)-TAMRA)-linked grafting cysteine-containing onto helped reduce caused over-bleaching. physicochemical properties (i.e. porosity) integrity changed bleaching. showed better permeability chemically treated [19]. Rhodamine B test bleached, photobleached abraded [20]. Sideris, Holt [21] rhodamine octadecylrhodamine (using same wool fibres). aliphatic alcohols Nile red, eosin Y heated 60°C 2 h solution prepared t-butanol. Following this, observed microscope. red intracellular regions completely. exhibited similar staining evenly stained Y, indicating complete authors explained observations taking account t-butanol (into cortex) affinities towards greater affinity preferential cuticle. Unlike positively believe interactions patterns [22]. Confocal uses sectioning technique, laser focused defined spot specific sample. Point-by-point imaging reconstruct three-dimensional [23]. Laser scanning confocal (rice bran oil, refined til oil liquid paraffin oil) hair, final (containing excipients), labelling results revealed mineral had vegetable oils. Final containing excipients, ability, highlighting influence could excipients [24]. To effectively investigation should density, contrasting particles emit wave assignment, change photon energy increases acceleration, helps detect compounds. bright-field dark-field created Transmission (TEM), serial-section (ssEM), (SEM), reflection transmission tunnelling cases, it consider internal temperature microscope maintain TEM). Cryo-TEM visualize heat. SEM capacity coloured silica nanoparticle virgin bleached Recorded holes nanoparticles surfaces. (and few techniques) understand best suitable [25]. immersed aqueous silver nitrate 10 min room Sodium hydroxide added alkalinity solution. precipitating inside Images resolution produced TEM (as compared SEM). captured TEM, proper [26]. identify efficient TEM. modified reduction-osmication method, usually visualizing cortex, human [27]. efficiency stain efficiencies stains bloc nitrate, uranyl acetate lead citrate-based section stains, phosphotungstic potassium permanganate ammoniacal nitrate). combination stains. ultrastructural features (under resolutions) used. provided contrast. advanced resources longer experimental needed, proved unsuitable large throughput [28]. electromagnetic radiations emitted atoms they return their ground state excited (after energy) characterization. spectrum absorb radiation type transition molecules. For example, transitions nuclear magnetic resonance radio spectrum. spacing between smallest cases. occur ultraviolet-visible (UV-Vis) region. commonly [29]. 1950s. detects intensity depends concentration evaluation. Photomultiplier tubes radiation. quantified device [30]. UV-Vis spectroscopy. X-ray Haake, Lagrené [31] silicones hydrocarbons shampoo-treated conclusive signals corresponding silicone moieties characterized before. dimethiconol (washed shampoo) detected Approximately half remained even cycles washing (with shampoo). Deppert Murphy [32] proposed adding isothiouronium moiety cationic whether prolonged. exposed adsorption experiment. Substantivity evaluated experiments materials. interactions, solubility formation keratin) [32]. Atomic (AES OES) 1970 multielement analysis. geo-analysis [33, 34]. metallurgical, environmental biological processes (analytical methods). AES elements sun stars [33]. measures atoms. state. Atomization achieved inductively coupled plasma (ICP), radiofrequency fields play roles ICP-AES ICP-OES) elemental analysis previously recorded [35]. aspects 34, 36]. aimed residues (from shampoo formulations) ICP-OES. Removability assays conducted sodium laureth sulphate. absorbed, 50% washing. second experiment, accentuated (3.5 times higher) Asiatic [31]. quantify metals hardness [37]. Virgin, brown Caucasian swatches subjected oxidative peroxide. washed hard water, dipped alkaline segregated based level Calcium magnesium possibly substances promote anionic sites, facilitating bond formation, low. calcium magnesium. increasing fact larger ionic radius, hydration radius (compared magnesium). easily anions Fourier transform infrared-attenuated reflectance (FTIR-ATR) groups vibrations. bands [38-40]. Infrared reflected ATR crystal placed. generates characterize [40, 41]. Itou, Nojiri [42] near-infrared (NIR) durability Chinese humidity organic acids. malic acid 20, 40 60 min. those obtained untreated Analysis NIR maps intensities NH amide stretching suggested number forming control groups). concluded efficiently occupy sites occupied water. improved humid [42]. FTIR microspectroscopy [43]. Black 30–120 peroxide (6%). I vibrations contained amines. Opening assisted bonds. By-products, especially cystine monoxide, released. quantity by-products time. Physical appearance square-shaped cross-sections inelastic elastic scattering impinges Inelastic basis collision photons continuous vibrational During process, there frequency scattered [44, 45]. Kuzuhara [46] acids, hydrolysed egg white incubated 1 16 50°C. hydrophobic aromatic rings, (even h). beta chains. remains almost constant indicated dispersed reduction thioglycerol permanent waving process [47]. (pH 9.0). adjusted ammonia monoethanolamine solutions (hair: 1:13). gauche-gauche-gauche gauche-gauche-trans conformations decreased trans-gauche-trans conformation increased. groups’ rearrangement, led thioglycolic both studied. diffused disconnection -SS- groups. degree (SIMS), sputtered ions. Numerous collisions ejection ions (positive, negative, neutral), then analysed [48]. (NanoSIMS) isotope-labelled chromophores (produced colouring process) Two deuterium-labelled perform black, deuterium melanin granules black Deuterium lacked [49]. resorcinol, salicylic pentadecyl-d31 pentadecanoic-d29 studied [50]. 2H/1H ratio evaluate lipophilicity (LogP) distribution labelled active Resorcinol LogP values ratios, permeation. lipids. makes easier Pentadecyl alcohol pentadecanoic medulla, remnants, layers values. quantities Kojima, Tsuji [51] palm (TOF-SIMS). Brunelle, Touboul [52] Saleem Galla [53] TOF-SIMS, particles, ionization, accelerated ‘flight tube’. determined measuring detector. accurate detection method. permanently waved. hydrogenated TOF-SIMS tripalmitin, constituent permeate outer [51]. Ruetsch Kamath [10] conditioners European TOF-SIMS. polyquaternium-10 (PQ-10) cetyltrimethylammonium bromide (CETAB) (high- respectively). positive negative CETAB (depth: ≥10 µm) throughout cross-section PQ-10 its non-unique fragments. properties, influenced conducting tests analyte identification quantification constituents. principle spectrophotometry [54]. divided radiations: (190–380 nm), (380–750 nm) (800–2500 classified spectrophotometers [55]. Silva Joekes [20] spectrophotometer. When saturation limit reached, 1.04 × 10–4 mol L−1 58–74% value). kinetics cortex). microspectrophotometry dyeing combined thiolactic L-cysteine [17, 56]. Electrostatic played role cysteine absent 9.0. On hand, abilities medium [56]. Hori [57] polyethyleneimine 11 independent [57]. Chromatography separating mixture. chromatographic separa