Visible Color Change Research Articles

Conformational polymorphs of isotretinoin and their impact on physicochemical and biological properties

Isotretinoin is the first-line drug for treatment of severe acne. Only one polymorph was reported even though it has been launched for nearly 40 years, and its clinic application was however limited by its stability and solubility challenges. In our study, two new polymorphs of isotretinoin were discovered and fully characterized. The transformation relationships between these solid forms were fully discussed, and a visible color change during single-crystal-to-single-crystal phase transition with the conformational change was investigated. Form II is determined to be thermodynamic stable form at room temperature, but metastable form at body temperature. The results show that form II is an ideal solid state possessing both superior thermal stability (60℃, open air) and higher absorption once delivered into body. The thermal stability can be associated with the crystal structure such as torsion angle. The relative bioavailability of form II is higher than form I as expected, and the bioavailability of form II formulation is about 2 times as that of the marketed form I capsule. Therefore, form II formulation could provide an alternative for better performing isotretinoin.

Mechanochromic behavior of a pyridine-containing pyrene derivative

Pyrene-based hydrazone derivative (PYI) which was synthesized from 1-pyrene formaldehyde and isoniazid presented a mechanochromic (MC) behavior and self-recovery performance at room temperature. Mild grinding of a PYI crystal would convert its fluorescence from weak blue to yellow. The metastable grinded PYI powders could revert to the original stable state at room temperature (RT) in 24 h. However, under the same conditions, the control molecule PYB did not exhibit MC property. The results showed that the MC behavior of PYI was caused by mechanical induced slippage of the pyrene dimers in the lattice, which altered the stacking behavior and molecular interactions. Because the two pyrene units in PYB dimer almost exhibited a sandwich-type arrangement, mechanical stimulus had little influence on the stacking state of PYB. Therefore, it did not exhibit the MC property. In addition, when mixed with oxalic acid and malonic acid, the fluorescence of pristine PYI was turned off, meanwhile with a visible color change from yellow to orange red. The phenomenon was a result of enhanced ICT effect between acidifying pyridine and pyrene unit.

Dipyrromethene chromo-fluorogenic chemosensors for quantitative detection and express analysis of Zn2+ ions

The dipyrromethene derivatives as new chromo-fluorogenic chemosensors for quantitative detection and express analysis of Zn2+ ions were synthesized and structural characterized. The sensing process of dipyrromethene toward Zn2+ was evaluated by UV–vis and fluorescence spectroscopy, molar ratios plots, and DFT calculations. The complexation of Zn(AcO)2 with dipyrromethenes in DMF solution was accompanied by significant bathochromic and hyperchromic effects in the electronic absorption spectra due to the formation of [ZnL2] complex. The 1:2 (Zn:HL) binding mode was proposed on the basis of absorption and theoretical studies. The complexation constants (lgKo) of Zn(AcO)2 with dipyrromethenes are from 8.1 to 10.9, which implying the potential of dipyrromethenes to acts as selective chemosensors for Zn2+. It is shown for the first time that the hexamethyl-substituted dipyrromethene could recognize Zn2+ ions in DMF solution through significant (almost 100 times) “off–on” fluorescent response caused by Zn2+ and visible color change from yellow to bright green under UV irradiation induced by formation of [ZnL2]. Hexamethyl-substituted dipyrromethene had high selectivity towards Zn2+ ions over many environmentally relevant ions, and high sensitivity with the detection limit in nanomolar level (4·10–8 mol/L). In terms of the thermodynamic constant and the fluorescence response of the complexation reaction of [ZnL2], as well as the detection limit of Zn2+ ions, dipyrromethene HL2 surpasses many Zn2+ sensors known in the literature. Dipyrromethenes can be a tool for detecting Zn2+ ions with simple test strips.

Spectroscopic and Colorimetric Studies for Anions with a New Urea-Based Molecular Cleft

A new simple urea-based dipodal molecular cleft (L) has been synthesized and studied for its binding affinity for a variety of anions by 1H-NMR, UV-Vis and colorimetric techniques in DMSO-d6 and DMSO, respectively. The results from titration studies suggest that the receptor forms a 1:2 complex with each of the anions used via hydrogen bonding interactions and exhibits strong selectivity for fluoride among halides, showing the binding affinity in the order of fluoride > chloride > bromide > iodide; meanwhile, it displays moderate selectivity for acetate among oxoanions, showing the binding affinity in the order of acetate > dihydrogen phosphate > bicarbonate > hydrogen sulfate > nitrate. Colorimetric studies of L for anions in DMSO reveal that the receptor is capable of detecting fluoride, acetate, bicarbonate and dihydrogen phosphate, displaying a visible color change in the presence of the respective anions.

μOPTO: A microfluidic paper-based optoelectronic tongue as presumptive tests for the discrimination of alkaloid drugs for forensic purposes

Natural and synthetic alkaloids are widely used for several applications, ranging from clinical purposes to criminal activities. Presumptive color tests are considered a leading tool to reveal on-scene substance identification via rapid chemical reactions that result in visual color changes. Colorimetric tests are popular due to their inherent simplicity, low cost, promptitude and portability; however, in many cases the results of such tests may not be predictable, partly because of the interference from similar species. In this proof-of-concept study, we present a paper-based microfluidic optoelectronic tongue – the so-called μOPTO – comprised of 6 indicators in lieu of one specific test and capable of discriminating 8 different alkaloid drugs (i.e. scopolamine, atropine, cocaine, morphine, ephedrine, caffeine, dipyrone and alprazolam) used for recreational, criminal and medical purposes. The wax printing method was employed to fabricate the microfluidic analytical device with six circular spots for reagent accommodation connected to a centered spot to enable simultaneous reactions with one sample injection. Digital images were obtained using an ordinary flatbed scanner, and the RGB information from before and after sample exposure was extracted using appropriate software. The color changes related to each spot were used to build differential maps with a unique fingerprint for each drug. The chemometric tools (i.e. PCA and HCA) showed suitable discrimination of all studied alkaloids in different quantities. To demonstrate a practical application, different alcoholic beverages spiked with scopolamine – a famous substance that causes drug abuse – were analyzed using the optoelectronic tongue. The results showed that small quantities of the drug were identified in different beverages, demonstrating that our device has the potential to be used in situ to prevent ingestion of contaminated samples.

A 4-phenyl thiophene appended 2,4-dinitrophenylhydrazone as a colorimetric chemosensor for selective detection of cyanide ion and its application for real-life samples

A Schiff's base probe PBD was synthesized by the treatment of 4-phenylthiophene-2-carbaldehyde and 2, 4-dinitrophenylhydrazine, which is found to act as a potential colorimetric sensor for CN− ion. The visual color change was noticed from yellow to pink with CN− ion in semi-aqueous medium due to the intra ligand charge transfer (ILCT) and deprotonation mechanism. The PBD-CN− complex formation was supported through NMR, UVVis absorption, and FT-IR spectral studies. The potential binding between probe and CN− ion were determined using Jobs plot (1:1 stoichiometric ratio) and density functional theory (DFT) calculations. The limit of detection was found to be 4.62 × 10−8 M, which is lesser than the permissible levels given by WHO in drinking water. Furthermore, the probe was tested for its reproducibility with various water samples, food samples and smartphone RGB technique to recognize CN− ion. The probe was successfully used for analysis of CN− ion in real samples.

Detection of Lysyl Oxidase Activity in Tumor Extracellular Matrix Using Peptide-Functionalized Gold Nanoprobes

Simple SummaryAlthough various malignant tumors express high levels of lysyl oxidase (LOX) and though its role in tumor progression is well-defined, there is a lack of sensing techniques to target LOX. This study highlights the application of peptide-functionalized gold nanoprobes for sensing the LOX levels in tumor microenvironments. The gold nanoparticles (AuNPs) in these nanoprobes aggregate upon exposure to LOX, resulting in a red shift of the surface plasmon resonance peak, accompanied by a characteristic color change. This colorimetric assay based on peptide-functionalized AuNP sensitively detects LOX secreted from various cancer cells not only in vitro but also in the tissue extract. In this study, the suggested analytical approach demonstrated high specificity to LOX and did not show any color change in the presence of other enzymes.High LOX levels in the tumor microenvironment causes the cross-linking of extracellular matrix components and increases the stiffness of tumor tissue. Thus, LOX plays an important role in tumorigenesis and in lowering the tumor response to anticancer drugs. Despite comprehensive efforts to identify the roles of LOX in the tumor microenvironment, sensitive and accurate detection methods have not yet been established. Here, we suggest the use of gold nanoparticles functionalized with LOX-sensitive peptides (LS-AuNPs) that aggregate upon exposure to LOX, resulting in a visual color change. LOX-sensitive peptides (LS-peptides) contain lysine residues that are converted to allysine in the presence of LOX, which is highly reactive and binds to adjacent allysine, resulting in the aggregation of the AuNPs. We demonstrated that the synthesized LS-AuNPs are capable of detecting LOX sensitively, specifically both in vitro and in the tissue extract. Moreover, the suggested LS-AuNP-based assay is more sensitive than commonly employed assays or commercially available kits. Therefore, the LS-AuNPs developed in this study can be used to detect LOX levels and can be further used to predict the stiffness or the anticancer drug resistance of the tumor.

Naphthalimide appended isoquinoline fluorescent probe for specific detection of Al3+ ions and its application in living cell imaging

Herein, a novel Schiff base fluorescent probe NIQ based on naphthalimide and iso-quinoline units has been readily prepared for the selective detection of Al3+ ions. The obviously visible color changes and prominent fluorescence enhancement were observed upon the addition of Al3+ to NIQ, which could be attributed to the complexation of NIQ with Al3+ and thus leading to the inhibition of photo-induced electron transfer (PET) and the chelation-enhanced fluorescence (CHEF) progress. The limit of detection (LOD) was 52 nM that was far below the standard recommended by the WHO. Binding ratio (1:1) of NIQ with Al3+ ions was supported by Job’s plot. The binding constant of NIQ for Al3+ were calculated to be 3.27 × 105 M−1 on the basis of benesi-Hildebrand plot. The plausible binding mechanism for NIQ towards Al3+ ions was evidenced by the density functional theory (DFT) and 1H NMR titration experiment. Furthermore, this “turn-on” probe NIQ has been successfully applied as a biomarker for imaging the Al3+ ions in living cells.

Development of a Loop-Mediated Isothermal Amplification Method for the Rapid Detection of Phytopythium vexans.

Brown root rot caused by Phytopythium vexans is a new destructive root disease on many plants such as Gingko, Citrus, kiwifruit, and ramie. The establishment of loop-mediated isothermal amplification (LAMP) technology for detecting P. vexans can help monitor and control brown root rot quickly, efficiently, and accurately. LAMP technology is known for its simplicity, sensitivity, and speed; and it does not require any specialized equipment – a water bath or a thermoblock is sufficient for isothermal amplifications. LAMP products can be visualized by using hydroxy naphthol blue (HNB) dye or agarose gel electrophoresis. In this study, by searching and comparing the internal transcribed spacer (ITS) sequences of P. vexans and the related species in oomycete genera Pythium, Phytopythium, and Phytophthora, we designed specific primers targeting the ITS gene region of P. vexans. Using HNB dye, we established a LAMP technique for rapid detection of P. vexans by visible color change. In addition, we optimized the protocol to enhance both sensitivity and specificity for P. vexans detection. Under the optimized condition, our protocol based on LAMP technology could detect as low as 24 copies of the P. vexans genomic DNA, which is ∼100 times more sensitive than conventional PCR. This method can successfully detect P. vexans using cell suspensions from P. vexans – infected ramie root tissues.

A BCNO QDs-MnO2 nanosheets based fluorescence “off-on-off” and colorimetric sensor with smartphone detector for the detection of organophosphorus pesticides

In this work, boron carbon oxynitride quantum dots (BCNO QDs) were prepared by a one-step hydrothermal process of ethanolamine and boric acid. BCNO QDs exhibited blue fluorescence with the optimal excitation/emission fluorescence peak at 335 and 420 nm, respectively. As an efficient fluorescence quencher, manganese dioxide (MnO2) nanosheets can effectively quench the fluorescence of BCNO QDs via the inner filter effect (IFE). Acetylcholinesterase (AChE) catalyzes the hydrolysis of acetylcholine (ATCh) to produce thiocholine (TCh). TCh can reductively degrade MnO2 nanosheets to generate Mn2+, thereby recovering the fluorescence of BCNO QDs. Organophosphorus pesticides (OPs) can inhibit the activity of AChE enzymes, thereby preventing the production of TCh and the decomposition of MnO2 nanosheets, resulting in the fluorescence “turn-off”. Therefore, the concentration of OPs can be detected by measuring the fluorescence intensity change of AChE-ATCh-MnO2-BCNO-QDs system. Under optimal experimental conditions, the dynamic detection range of paraoxon is 0.1–250 ng mL−1, and the detection limit is 0.03 ng mL−1. Meanwhile, the reaction system also showed concentration-dependent visual color changes from colorless to brownish. Furthermore, we prepared a portable BCNO QDs test paper. By using a smartphone to identify the RGB values of the reaction solution and the corresponding test paper, we carried out the digital image chromaticity analysis, which can shorten the detection time and reduce the detection cost, and provide an effective solution for the rapid detection of OPs on site.

Fabrication of Pd@ZnNi‐MOF/GO Nanocomposite and Its Application for H2O2 Detection and Catalytic Degradation of Methylene Blue Dyes

AbstractZnNi‐MOF/GO hybrid with layered structures were synthesized by a simple solvothermal method. We use ZnNi‐MOF/GO as the support material for Pd nanoparticles, and synthesize a highly active Pd@ZnNi‐MOF/GO nanocomposite. The structure, morphology and composition of the nanocomposite were studied by X‐ray diffraction (XRD), transmission electron microscopy (TEM), and X‐ray photoelectron spectroscopy (XPS). In addition, Pd@ZnNi‐MOF/GO nanocomposite can be called a nanozyme with peroxidase‐like activity, the nanocomposite was applied for the detection of hydrogen peroxide (H2O2) and the degradation of methylene blue (MB) dyes. The nanocomposite showed the high peroxidase‐like activity towards 3,3′,5,5′‐tetramethylbenzidine (TMB) with a visual color change in the presence of H2O2. The nanocomposite also showed the good catalytic activity in the degradation of methylene blue dyes. The nanocomposite has the advantages of convenient preparation, good stability, and excellent reproducibility. Hence, Pd@ZnNi‐MOF/GO is a promising catalyst with wide application.

A Highly Selective and Sensitive Colorimetric Chemosensor for the Detection of Hydrogen Sulfide: A Real‐time Application in Multiple platforms

Calorimetric chemosensors are found to be advantageous sensing systems due to their simplicity and favorable responsive properties. Although some colorimetric probes have been reported to detect hydrogen sulfide (H2 S), the creation of rapid, highly selective and sensitive probes for the detection of H2 S remains a challenging target. In this work, we established dinitrosulphonamide decorated phenanthridine and 2,4-dinitro-N-(4-(7,8,13,14-tetrahydrodibenzo[a, i]phenanthridin-5-yl)phenyl)benzenesulfonamide (PHSH), for the calorimetric detection of H2 S. H2 S-triggered thiolysis of PHSH resulted in a marked absorption enhancement alongside a visual color change from colorless to dark yellow. The result indicated that the chemosensor showed high sensitivity and selectivity with a fast response of less than 10 s with a detection limit as low as 6.5 nM. The chemosensor reaction mechanism with H2 S was studied by UV-vis, 1 H NMR, mass and HPLC analysis. In addition, the chemosensor has been used for the determination of H2 S in many real-time samples.

An AIE-active probe for selective fluorometric–colorimetric detection of HSO3− in aqueous solution and real samples

We report herein a new biphenylcarbonitrile derivative, 4′-hydroxy-3′ -((2-imidazolylimino) methyl)-4-biphenyl carbonitrile (HIBC), which interestingly exhibits an aggregation-induced emission property. HIBC was employed for selective dual mode (fluorimetric and colorimetric) assay of HSO3− ions in nearly 100% aqueous medium at pH 7.4. The nucleophilic addition of HSO3− on the imino group in HIBC breaks its π-electron conjugation and results in a noticeable absorption and fluorescence spectral changes accompanied by a visible color change. Moreover, the formation of anionic addition product weakened the aggregation effect and meanwhile inhibited ESIPT process in HIBC, causing quenching of keto fluorescence of the probe. The probe shows good selectivity for HSO3− ions over all other competitive anions, which renders it a promising candidate for ratiometric fluorescent assay of HSO3− in aqueous systems. The limit of detection is 1.83 × 10−7 mol/L. For the practical applicability, handy paper strips were fabricated from HIBC for convenient recognition of HSO3−. Additionally, HIBC was applied for the living HeLa cells bio-imaging.

A highly sensitive ratiometric fluorescent sensor for copper ions and cadmium ions in scallops based on nitrogen doped graphene quantum dots cooperating with gold nanoclusters

Based on the electrostatic interaction, we constructed a ratiometric fluorescence nanomixture of graphene quantum dots-gold nanoclusters (GQDs-AuNCs) for the quantitative detection of Cu2+ and Cd2+. When Cu2+ or Cd2+ was added into the reaction system, the fluorescence of GSH-AuNCs at 565 nm can be quenched by Cu2+ and enhanced by Cd2+ while the intensity of N-GQDs at 403 nm stayed constant. Under the optimized conditions, the fluorescence intensity ratio (I565/I403) of the GQDs-AuNCs system was proportional to the concentration of Cu2+ and Cd2+ in the range of 8×10−8 mol/L-6×10−6 mol/L and 1×10−6 mol/L-4×10−5 mol/L, respectively, with detection limits of 4.12×10−9 mol/L and 9.43×10−7 mol/L, respectively. In the presence of Cu2+ and Cd2+, the paper-based vision sensor would produce visible fluorescent color changes, which can be used for rapid detection on site. The method has been successfully applied to the determination of Cu2+ and Cd2+ in scallops with satisfactory results.

Cesium Lead Bromide Perovskite Nanocrystals as a Simple and Portable Spectrochemical Probe for Rapid Detection of Chlorides

AbstractThe wide spectral tunability of CsPbBr3 perovskite nanocrystals (NCs) via instantaneous and facile anion exchange, make them a suitable candidate for chloride detection. Rapid anion‐exchange processes between CsPbBr3 perovskite NCs and different chloride solutions were carried out in ambient conditions. The resultant anion‐exchanged CsPbCl3‐xBrx NCs preserved the structural properties and exhibited a remarkable blue‐shift in photoluminescence spectra. This form a basis for detection of chloride ions in water. This has been applied with the limit of detection upto 100 μM. The detection strategies were not only limited to the direct addition of chloride solutions to NCs, but also showed a visual colour change under UV light when the chloride solution is drop‐casted on CsPbBr3 films that are deposited on glass substrates. Furthermore, the detection strategy is established by drop‐casting CsPbBr3 NCs onto paper strips that are pre‐soaked in chloride solutions. A considerable blue‐shift in fluorimetry proves them to be an excellent sensing medium as practical spectrochemical probes for on‐site detection of chlorides. Based on this, a colour chart and selectivity chart to access the presence of chlorides and their concentration is demonstrated here.

A novel and sensitive colorimetric detection of PABA by asymmetrically functionalized TA-AuNPs-PEG-FITC based on oriented aggregation

A colorimetric assay based on the oriented TA-AuNPs-PEG-FITC for rapid and sensitive PABA detection was proposed. Initially, the negatively charged TA modified on the surface of AuNPs enabled rapid binding to PABA due to the electrostatic interaction and hydrogen bond, resulting in a visible color change. However, particles were aggregated in a non-oriented way, leading to an unstable testing system which failed to realize the accurate quantification. Thus, the asymmetrically functionalized TA-AuNPs-PEG-FITC were prepared, in which the stabilizer agent of HS-PEG-FITC was attached to the specific sites on the surface of TA-AuNPs. Such a way of modification resulted in an oriented aggregation manner, the addition of PABA induced the formation of oligomers. Moreover, the introduction of FITC group acted as fluorescent marker, providing a simple, fast and quantitative method for characterization of PEG chain. The molar ratio between TA-AuNPs and modified PEG-FITC was further determined. A linear regression was established in a wide range from 10 μM to 1 mM with the LOD of 6.9 μM. Finally, the sensor was successfully applied in the health food. This was the first example in which TA-AuNPs-PEG-FITC were fabricated for colorimetric detection of PABA, and an indirect method based on fluorescence marker was well used to quantify the content of PEG chain.

Fluorescence detection of perfluorooctane sulfonate in water employing a tetraphenylethylene-derived dual macrocycle BowtieCyclophane

Because the widely used perfluorooctane sulfonate (PFOS) is harmful to both environment and human health, it is of great significance and urgency to develop sensitive and selective sensors for the detection of trace PFOS in water. In this study, a tetraphenylethylene-derived macrocycle BowtieCyclophane has been developed as a fluorescent sensor based on aggregation-induced emission enhancement and fluorochromism. Sensitive detection of PFOS has been achieved with a limit of detection (LOD) of 47.3 ± 2.0 nmol/L (25.4 ± 1.1 µg/L) accompanied by visual fluorescence color changes.

Use of Aerial Roots of Ficus benghalensis for Green Synthesis of Silver Nanoparticles with Enhanced Antibacterial Activity

Basically, nanosubstances are developed by a variety of chemical methods which are not environmentally providential.
 Aim: The present research work deals with the synthesis of silver nanoparticles using the aerial root of Ficus benghalensis extract. The absolute reduction of silver ions was observed after 48 h of reaction when extact combine with aqueous solution of Silver nitrate. The visual colour changes were observed during the reduction of silver ion into the silver nanoparticles in the reaction mixture allows producing dark brown colour. The formed silver nanoparticles was purified by high speed centrifugation, collected and stored for further characterization.
 Methodology: The formation of silver nanoparticles was confirmed by UV-Visible spectroscopy, and characterised by X-Ray Diffraction (XRD) pattern, FTIR, High Resolution Transmission Electron Microscopy (HRTEM), Zeta potentiometry, ICP-AES.
 Results: The results showed that UV peak at 437.5 nm, the silver content estimation by ICP-AES was found to be 413.06 µg/mL and images were recorded by using High resolution TEM. Synthesized AgNPs were found to be effective against micro-organisms responsible for bacterial infections like Staphylococcus aureus, Pseudomonas aeruginosa, E. coli and Methicillin resistant Staphylococcus Aureus (MRSA). Further In-vitro cytocompatibility studies showed lack of toxicity at even higher concentration. 
 Conclusion: Still, these Silver Nanoparticles are cytotoxic in nature and could serve as a good green method for synthesis of silver nanoparticle by using plant extract.

Development of Novel Antimicrobial and Antiviral Green Synthesized Silver Nanocomposites for the Visual Detection of Fe3+ Ions.

In the current research, we present a single-step, one-pot, room temperature green synthesis approach for the development of functional poly(tannic acid)-based silver nanocomposites. Silver nanocomposites were synthesized using only tannic acid (plant polyphenol) as a reducing and capping agent. At room temperature and under mildly alkaline conditions, tannic acid reduces the silver salt into nanoparticles. Tannic acid undergoes oxidation and self-polymerization before the encapsulating of the synthesized silver nanoparticle and forms silver nanocomposites with a thick capping layer of poly(tannic acid). No organic solvents, special instruments, or toxic chemicals were used during the synthesis process. The results for the silver nanocomposites prepared under optimum conditions confirmed the successful synthesis of nearly spherical and fine nanocomposites (10.61 ± 1.55 nm) with a thick capping layer of poly(tannic acid) (~3 nm). With these nanocomposites, iron could be detected without any special instrument or technique. It was also demonstrated that, in the presence of Fe3+ ions (visual detection limit ~20 μM), nanocomposites aggregated using the coordination chemistry and exhibited visible color change. Ultraviolet-visible (UV–vis) and scanning electron microscopy (SEM) analysis also confirmed the formation of aggregate after the addition of the analyte in the detection system (colored nanocomposites). The unique analytic performance, simplicity, and ease of synthesis of the developed functional nanocomposites make them suitable for large-scale applications, especially in the fields of medical, sensing, and environmental monitoring. For the medical application, it is shown that synthesized nanocomposites can strongly inhibit the growth of Escherichia coli and Staphylococcus aureus. Furthermore, the particles also exhibit very good antifungal and antiviral activity.

Covalent immobilization of bromocresol purple on cellulose nanocrystals for use in pH-responsive indicator films

This study developed pH-indicator films by combining esterified cellulose nanocrystals (e-CNCs) with activated bromocresol purple (a-BCP) via covalent bonding for pH-sensitive color-changing applications. The e-CNC/a-BCP particles were incorporated into cellulose acetate polymer to prepare pH-sensitive color changing films. Binding of a-BCP to e-CNCs was proven by attenuated total reflection infrared (ATR-IR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Colorimetric analysis showed that films containing 10% or 15% e-CNC/a-BCP particles had critical color changes either at pH 4–5, or pH 7–8. The films with 10% e-CNC/a-BCP particles also revealed excellent leaching resistance under acidic conditions. Color changes were reversible between pH 2 and 10. These pH-indicator films had visible color changes in response to pH variations, color reversibility, leaching resistance, and sufficient rigidity even though mechanical properties decreased as the e-CNC/a-BCP content increased from 0% to 15%.