Reversible two-way tuning of thermal conductivity in an end-linked star-shaped thermoset.

Polymeric thermal switches that can reversibly tune and significantly enhance their thermal conductivities are desirable for diverse applications in electronics, aerospace, automotives, and medicine; however, they are rarely achieved. Here, we report a polymer-based thermal switch consisting of an end-linked star-shaped thermoset with two independent thermal conductivity tuning mechanisms-strain and temperature modulation-that rapidly, reversibly, and cyclically modulate thermal conductivity. The end-linked star-shaped thermoset exhibits a strain-modulated thermal conductivity enhancement up to 11.5 at a fixed temperature of 60 °C (increasing from 0.15 to 2.1 W m-1 K-1). Additionally, it demonstrates a temperature-modulated thermal conductivity tuning ratio up to 2.3 at a fixed stretch of 2.5 (increasing from 0.17 to 0.39 W m-1 K-1). When combined, these two effects collectively enable the end-linked star-shaped thermoset to achieve a thermal conductivity tuning ratio up to 14.2. Moreover, the end-linked star-shaped thermoset demonstrates reversible tuning for over 1000 cycles. The reversible two-way tuning of thermal conductivity is attributed to the synergy of aligned amorphous chains, oriented crystalline domains, and increased crystallinity by elastically deforming the end-linked star-shaped thermoset.

Reinforced dentin remineralization via a novel dual-affinity peptide.

OBJECTIVES: In light of the constantly flowing saliva, anti-caries remineralization agents are inclined to be taken away. Owing to their limited residence time, the remineralization effect is not as desirable as expected. Hence, our study aimed to synthesize a novel peptide (DGP) with high affinity to both collagen fibrils and hydroxyapatite, and investigated its dentin remineralization efficacy in vitro and anti-caries capability in vivo. METHODS: DGP was synthesized through Fmoc solid-phase reaction. The binding ability and interaction mechanism of DGP to demineralized dentin were investigated. Dentin specimens were demineralized, then treated with DGP and deionized water respectively. The specimens were incubated in artificial saliva and in-vitro remineralization effectiveness was analyzed after 14 days. The rat caries model was established to further scrutinize the in-vivo efficacy of caries prevention. RESULTS: DGP possesses an enhanced adhesion force of 12.29 ± 1.12 nN to demineralized dentin. The favorable adsorption capacity is ascribed to the stable hydrogen bonds between S2P-101 and ASP-100 of DGP and GLY33 and PRO-16 of collagen fibers. Abundant mineral deposits and remarkable tubule occlusion were observed in the DGP group. DGP-treated dentin obtained notable microhardness recovery and higher mineral content after a 14-day remineralization regimen. DGP also demonstrated potent caries prevention in vivo, with substantially fewer carious lesions and significantly lower Keyes scoring. SIGNIFICANCE: DGP proves to possess a high affinity to demineralized dentin regardless of saliva flowing, thus enhancing remineralization potency significantly in vitro and in vivo, potential for dental caries prevention and combatting initial dentin caries clinically.

Metronidazole and Ketoprofen-Loaded Mesoporous Magnesium Carbonate for Rapid Treatment of Acute Periodontitis In Vitro.

In the clinical pharmacological treatment of acute periodontitis, local periodontal administration is expected to be preferable to systemic administration. However, the action of the active medicine component is hindered and diminished by the limitation of drug solubility, which does not provide timely relief of the enormous pain being suffered by patients. This study aimed to develop a mesoporous magnesium carbonate (MMC) medicine loading system consisting of MMC, metronidazole (MET), and ketoprofen (KET), which was noted as MET-KET@MMC. A solvent evaporation process was utilized to load MET and KET in MMC. Scanning electron microscopy, nitrogen sorption, thermogravimetric analysis, and X-ray diffraction were performed on the MET-KET@MMC. The rapid drug release properties were also investigated through the drug release curve. The rapid antiseptic property against Porphyromonas gingivalis (P. gingivalis) and the rapid anti-inflammatory property (within 1 min) were analyzed in vitro. The cytotoxicity of MET-KET@MMC was tested in direct contact with human gingival cells and human oral keratinocytes. Crystallizations of MET and KET were completely suppressed in MMC. As compared to crystalline MET and KET, MMC induced higher apparent solubility and rapid drug release, resulting in 8.76 times and 3.43 times higher release percentages of the drugs, respectively. Over 70.11% of MET and 85.97% of KET were released from MMC within 1 min, resisting bacteria and reducing inflammation. MET-KET@MMC nanoparticles enhanced the solubility of drugs and possess rapid antimicrobial and anti-inflammatory properties. The MET-KET@MMC is a promising candidate for the pharmacotherapy of acute periodontitis with drugs, highlighting a significant clinical potential of MMC-based immediate drug release systems.

An engineered dual-functional peptide with high affinity to demineralized dentin enhanced remineralization efficacy in vitro and in vivo.

Dental caries continues to be a major global public health problem. Remineralization of demineralized dentin is regarded as one of the hotspots in the current study in the treatment of dental caries. However, traditional remineralization agents, which usually lack the ability to bind to demineralized dentin collagen, are easily removed by the fluids in the oral cavity, thus decreasing the remineralization efficacy. Non-collagenous proteins (NCPs) have significant effects on the biomineralization of dentin due to their dual high binding capacity to the collagen fibers and minerals. But NCPs are hard to extract, store and use directly. Inspired by the biological behavior of NCPs, in this study, we selected two functional sequences of NCPs to develop a novel and engineered dual-functional peptide (which is referred to as CYP) with collagen-binding and mineral-absorbing capability. The binding ability of CYP to collagen fibers and demineralized dentin was investigated, and the results suggested that CYP was endowed with good binding capacity to demineralized dentin, which could resist the washing of the fluid. In addition, we confirmed that CYP exerted formidable remineralization effects in collagen fibers and demineralized dentin following an in vitro remineralization regimen. Furthermore, the dual functions of CYP with good biocompatibility can simultaneously bind collagen and induce nanocrystal precipitation, thereby significantly absorbing calcium and phosphorus ions to form regenerated minerals for reversing the tooth decay process in the rat caries model. Overall, the dual functional peptide CYP fabricated in this study provides an ideal and smart strategy for dentin remineralization and the treatment of caries.

Reversible Photochromic Photonic Crystal Device with Dual Structural Colors.

Photonic crystal (PhC) light emitter (PC-LE) devices attract extensive attention in anticounterfeiting for their manipulated light emission and iridescent structural color, but their large-scale three-dimensional fabrication is still limited by poor mechanical strength and microstructural defects. Herein, colloidal nanospheres incorporated with photoluminescent dye were assembled to three-dimensional PC-LE devices through a large-scale compressing-induced strategy, which realized dual iridescent and reversible photochromic colors. Periodically distributed refractive indices between molten molecular chains and cross-linked nanospheres generated the iridescent structural color. Subsequently, the device surface reflected another different structural color after partially removing the surface molecular chains by etching. The light emission intensity of the dye was sufficient to obtain the reversible photochromic colors. Simultaneously, the manipulation toward light emission of the photonic band gap achieved the shape of the photoluminescent intenstiy spectra that varied in accordance with the reflective peak. Furthermore, by use of screen-printing tools and transparent masking glue, the etching process became an inkless color printing process, generating a colorful bar code (2 cm × 2 cm) on the device surface. The code was reversibly displayed and encrypted through control of the reflection and emission of light. Significantly, the PC-LE devices opened up a new route for advanced display, color printing, and anticounterfeiting stickers.

Fast-Response Bioinspired Near-Infrared Light-Driven Soft Robot Based on Two-Stage Deformation.

Herein, we report a remotely controlled soft robot employing a photoresponsive nanocomposite synthesized from liquid crystal elastomers (LCEs), high elastic form-stable phase change polymer (HEPCP), and multiwalled carbon nanotubes (MWCNTs). Possessing a two-stage deformation upon exposure to near-infrared (NIR) light, the LCE/HEPCP/MWCNT (LHM) nanocomposite allows the soft robot to exhibit an obvious, fast, and reversible shape change with low detection limitations. In addition to the deformation and bending of the LCE molecular chains itself, the HEPCP in the composite material can also be triggered by a reversible solid-liquid transition due to the temperature rise caused by MWCNTs, which further promotes the change of the LCE. In particular, the proposed photodriven LHM soft robot can bend up to 180° in 2 s upon NIR stimulation (320 mW, distance of 5 cm) and generate recoverable, dramatic, and sensitive deformation to execute various tasks including walking, twisting, and bending. With the capacity of imitating biological behaviors through remote control, the disruptive innovation developed here offers a promising path toward miniaturized untethered robotic systems.

Speaking-Induced Charge-Laden Face Masks with Durable Protectiveness and Wearing Breathability.

Face masks, which serve as personal protection equipment, have become ubiquitous for combating the ongoing COVID-19. However, conventional electrostatic-based mask filters are disposable and short-term effective with high breathing resistance, causing respiratory ailments and massive consumption (129 billion monthly), intensifying global environmental pollution. In an effort to address these challenges, the introduction of a piezoelectric polymer was adopted to realize the charge-laden melt-blown via the melt-blowing method. The charge-laden melt-blown could be applied to manufacture face masks and to generate charges triggered by mechanical and acoustic energy originated from daily speaking. Through an efficient and scalable industrial melt-blown process, our charge-laden mask is capable of overcoming the inevitable electrostatic attenuation, even in a high-humidity atmosphere by long-wearing (prolonging from 4 to 72 h) and three-cycle common decontamination methods. Combined with outstanding protective properties (PM2.5 filtration efficiency >99.9%), breathability (differential pressure <17 Pa/cm2), and mechanical strength, the resultant charge-laden mask could enable the decreased replacement of masks, thereby lowering to 94.4% of output masks worldwide (∼122 billion monthly) without substituting the existing structure or assembling process.

Acoustic Core-Shell Resonance Harvester for Application of Artificial Cochlea Based on the Piezo-Triboelectric Effect.

The demand for flexible, efficient, and self-powered cochlear implants applied to remedy sensorineural hearing loss caused by dysfunctional hair cells remains urgent. Herein, we report an acoustic core-shell resonance harvester for the application of artificial cochleae based on the piezo-triboelectric effect. Integrating dispersed BaTiO3 particles as cores and porous PVDF-TrFE as shells, the acoustic harvest devices with ingenious core-shell structures exhibit outstanding piezo-triboelectric properties (Voc = 15.24 V, DAsc = 9.22 mA/m2). The acoustic harvest principle reveals that BaTiO3 nanocores resonate with sound waves and bounce against porous PVDF-TrFE microshells, thereby generating piezo-triboelectric signals. By experimental measurement and numerical modeling, the vibration process and resonance regulation of acoustic harvest devices were intensively investigated to regulate the influential parameters. Furthermore, the acoustic harvesters exhibit admirable feasibility and sensitivity for sound recording and show potential application for artificial cochlea.

Nanoporous PVDF Hollow Fiber Employed Piezo-Tribo Nanogenerator for Effective Acoustic Harvesting.

Restricted by the inherent property of low power density, acoustic energy can hardly be effectively captured by conventional piezo- or triboelectric nanogenerators for powering miniature electronics. Herein, a novel piezo-tribo hybrid nanogenerator employing nanoporous polyvinylidene fluoride (PVDF) hollow fiber and polydimethylsiloxane (PDMS) valve, which can mimic the eardrum, has been advocated for efficient acoustic harvesting. The nanoporous, hollow, and valve structure design, together with the effective combination of piezo- and triboelectricity, make the nanoporous PVDF hollow fiber and PDMS valve based acoustic harvester (PHVAH) a promising candidate for acoustic-electric conversion. With an optimal output of 105.5 V and 16.7 µA and a power density of 0.92 W m-2 under the sound stimulation of 117.6 dB and 150 Hz, it can not only recognize audio signals but also convert the sound into electrical energy to light up seven LED bulbs in series. Exhibiting excellent durability and stability, the disruptive innovation proposed here is an effective method for hunting the ubiquitous sound energy in the environment, which provides great potential and impetus for using acoustic-electric conversion to power various low-power-consumption sensors.

Remineralization effectiveness of adhesive containing amorphous calcium phosphate nanoparticles on artificial initial enamel caries in a biofilm-challenged environment.

OBJECTIVES: Dental caries is closely associated with acid-producing bacteria, and Streptococcus mutans is one of the primary etiological agents. Bacterial accumulation and dental demineralization lead to destruction of bonding interface, thus limiting the longevity of composite. The present study investigated remineralization effectiveness of adhesive containing nanoparticles of amorphous calcium phosphate (NACP) in a stimulated oral biofilm environment. METHODS: The enamel blocks were immersed in demineralization solution for 72 h to imitate artificial initial carious lesion and then subjected to a Streptococcus mutans biofilm for 24 h. All the samples then underwent 4-h demineralization in brain heart infusion broth with sucrose (BHIS) and 20-h remineralization in artificial saliva (AS) for 7 days. The daily pH of BHIS after 4-h incubation, lactic acid production, colony-forming unit (CFU) count, and content of calcium (Ca) and phosphate (P) in biofilm were evaluated. Meanwhile, the remineralization effectiveness of enamel was analyzed by X-ray diffraction (XRD), surface microhardness testing, transverse microradiography (TMR) and scanning electron microscopy (SEM). RESULTS: The NACP adhesive released abundant Ca and P, achieved acid neutralization, reduced lactic acid production, and lowered CFU count (P < 0.05). Enamel treated with NACP adhesive demonstrated the best remineralization effectiveness with remineralization value of 52.29 ± 4.79% according to TMR. Better microhardness recovery of cross sections and ample mineral deposits were also observed in NACP group. CONCLUSIONS: The NACP adhesive exhibited good performance in remineralizing initial enamel lesion with cariogenic biofilm. SIGNIFICANCE: The NACP adhesive is promising to be applied for the protection of bonding interface, prevention of secondary caries, and longevity prolonging of the restoration.

Adhesion of Streptococcus mutans on remineralized enamel surface induced by poly(amido amine) dendrimers.

The aim of this study was to investigate the surface topography of remineralized enamel induced by poly(amido amine) (PAMAM) dendrimers and evaluate Streptococcus mutans (S. mutans) adhesion on regenerated enamel for the first time. PAMAM-COOH and PAMAM-NH2 were used as organic templates to induce enamel surface remineralization. The mineral deposits after remineralization were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The surface topography of the remineralized enamel was analyzed by atomic force microscopy (AFM). An AFM tipless cantilever was functionalized with S. mutans and acted as a force probe to measure the adhesion force between bacteria and the remineralized enamel surface. Colony-forming unit (CFU) counts of biofilm on remineralized enamel surface were performed after 24 h incubation in S. mutans suspension. Both PAMAM-COOH and PAMAM-NH2 achieved effective remineralization on demineralized enamel surfaces, which smoothed the enamel surface and reduced S. mutans adhesion. PAMAM dendrimers are promising materials for early caries treatment because of their excellent remineralization ability. The remineralization induced by PAMAM dendrimers smoothed the surface and reduced S. mutans adhesion, which could prevent secondary caries.

Opening the Soul Window Manually: Limbal Tissue Scaffolds with Electrospun Polycaprolactone/Gelatin Nanocomposites.

Restricted by the difficulty in fabricating scaffolds suitable for cell proliferation, the use of ex vivo expanded limbal stem cell (LSC) for LSC transplantation, an effective treatment method for patients with limb stem cell deficiency (LSCD), is hard to be widely used in clinical practice. To tackle these challenges, a novel electrospun polycaprolactone (PCL)/gelatin nanocomposite is proposed to make 3D scaffolds for limbal niche cells (LNC) proliferation in vitro, which is a milestone in the treatment of diseases such as LSCD. PCL and gelatin in different weight ratios are dissolved in a mixed solvent, and then electrospinning and cross-linking are performed to prepare a scaffold for cell proliferation. The characterizations of the nanocomposites indicate that the gelatin content has a significant effect on its micro-morphology, thermal properties, crystallinity, degradation temperature, hydrophilicity, and mechanical properties. P8G2-C (PCL: gelatin = 80: 20, cross-linked), with smooth fibers and homogeneous pores, has better hydrophilicity, mechanical properties, and flexibility, so it can support LNC as cell proliferation assays revealed. This detailed investigation presented here demonstrates the feasibility of using PCL/gelatin nanocomposites electrospun fiber membranes as a limbus tissue engineering scaffold, which undoubtedly provide a new perspective for the development of tissue engineering field.

Rechargeable adhesive with calcium phosphate nanoparticles inhibited long-term dentin demineralization in a biofilm-challenged environment.

OBJECTIVES: This study aims to investigate the long-term demineralization-inhibition capability of a rechargeable adhesive with nanoparticles of amorphous calcium phosphate (NACP) on dentin in a biofilm-challenged environment. METHODS: The NACP adhesive was immersed in a pH 4 solution to exhaust calcium (Ca) and phosphate (P) ions and then recharged with Ca and P ions. Dentin samples were demineralized underStreptococcus mutans biofilms for 24 h and randomly divided into two groups: (1) dentin control, (2) dentin with recharged NACP adhesives. Each day, all the samples were immersed in brain heart infusion broth with 1% sucrose (BHIS) for 4 h, and then in artificial saliva (AS) for 20 h. This cycle was repeated for 10 days. The pH of BHIS, the Ca and P ions content of the BHIS and AS were measured daily. After 10 days, the lactic acid production and colony-forming units of the biofilms were tested. The changes of remineralization/demineralization were also analyzed. RESULTS: Dentin in the control group showed further demineralization. The recharged NACP adhesive neutralized acids, increasing the pH to above 5, and released large amounts of Ca and P ions each day. The recharged NACP adhesive decreased the production of lactic acid (P < 0.05), inhibited dentin demineralization and sustained the dentin hardness in the biofilm-challenged environment, showing an excellent long-term demineralization-inhibition capability. CONCLUSIONS: The NACP adhesive could continuously inhibit dentin demineralization in a biofilm-challenged environment by recharging with Ca and P ions. SIGNIFICANCE: The rechargeable NACP adhesive could provide long-term dentin bond protection.

Nano-calcium phosphate and dimethylaminohexadecyl methacrylate adhesive for dentin remineralization in a biofilm-challenged environment.

OBJECTIVE: Dentin remineralization at the bonded interface would protect it from external risk factors, therefore, would enhance the longevity of restoration and combat secondary caries. Dental biofilm, as one of the critical biological factors in caries formation, should not be neglected in the assessment of caries preventive agents. In this work, the remineralization effectiveness of demineralized human dentin in a multi-species dental biofilm environment via an adhesive containing nanoparticles of amorphous calcium phosphate (NACP) and dimethylaminohexadecyl methacrylate (DMAHDM) was investigated. METHODS: Dentin demineralization was promoted by subjecting samples to a three-species acidic biofilm containing Streptococcus mutans, Streptococcus sanguinis, Streptococcus gordonii for 24h. Samples were divided into a control group, a DMAHDM adhesive group, an NACP group, and an NACP+DMAHDM adhesive group. A bonded model containing a control-bonded group, a DMAHDM-bonded group, an NACP-bonded group, and an NACP+DMAHDM-bonded group was also included in this study. All samples were subjected to a remineralization protocol consisting of 4-h exposure per 24-h period in brain heart infusion broth plus 1% sucrose (BHIS) followed by immersion in artificial saliva for the remaining period. The pH of BHIS after 4-h immersion was measured every other day. After 14 days, the biofilm was assessed for colony-forming unit (CFU) count, lactic acid production, live/dead staining, and calcium and phosphate content. The mineral changes in the demineralized dentin samples were analyzed by transverse microradiography. RESULTS: The in vitro experiment results showed that the NACP+DMAHDM adhesive effectively achieved acid neutralization, decreased biofilm colony-forming unit (CFU) count, decreased biofilm lactic acid production, and increased biofilm calcium and phosphate content. The NACP+DMAHDM adhesive group had higher remineralization value than the NACP or DMAHDM alone adhesive group. SIGNIFICANCE: The NACP+DMAHDM adhesive was effective in remineralizing dentin lesion in a biofilm model. It is promising to use NACP+DMAHDM adhesive to protect bonded interface, inhibit secondary caries, and prolong the longevity of restoration.

Three-Dimensional Photonic Crystal Bulks with Outstanding Mechanical Performance Assembled by Thermoforming-Etching Cross-linked Polymer Microspheres.

Traditional self-assembly methods for photonic crystals (PCs) limited by poor mechanical performance and microstructure defects make it hard to be directly applied to optical devices, whose performance strongly rely on mechanical performance and microstructure of PCs. Here, a thermoforming-etching strategy combining both traditional processing and nanofabrication is reported to develop cross-linked polystyrene microsphere-based PC bulks with outstanding mechanical performance. It illustrates scientific principles, where surface molecular chains of PS microspheres were activated and entangled with each other under thermoforming conditions (200 °C; 220 MPa), resulting in applicable mechanical strength (hardness and modulus reach 0.12 and 4.12 GPa, respectively). The optimum optical reflectivity of the PS microsphere-based (180 nm) PC bulk is 49.4% at 381 nm. Furthermore, these PC bulks have been successfully written in anti-counterfeiting and realized colorful pattern printing. The innovative method opens a new route for the rapid and simple fabrication of the nanoparticle structure which can be used as various functional devices and directly promotes the industrialization of bulk PC devices, such as optical and display devices, and so forth.

Self-Powered Infrared-Responsive Electronic Skin Employing Piezoelectric Nanofiber Nanocomposites Driven by Microphase Transition.

Infrared light (IR) detection principles limited by poor photoresponsivity and sparse photogenerated carrier make them impossible to directly applied in flexible IR sensing field attributed to low π-π conjugation effect, thick P-N junction, and harsh band gap, of which IR self-powered electronic skin (e-skin) strongly relies on the essential property of exotic photosensitive-exciting materials, hardly any flexible organic polymer or nanocomposites. Here, an innovative IR self-powered principle is reported that outstanding piezoelectric effect of poly(vinylidene fluoride) nanofibers (PVDF NFs) is driven by microcrystals' volume expansion caused by the solid-solid phase transition of PVDF/multiwalled carbon nanotubes (MWCNTs)/highly elastic phase change polymer (HEPCP) (PMH) nanocomposites due to MWCNT's excellent IR photoabsorption and thermal conversion capabilities. A flexible IR-sensitive nanocomposite is successfully developed employing PVDF/HEPCP NFs as the framework of a three-dimensional network structure wrapped by the MWCNT/HEPCP nanocomposite. The 33, 50, and 60 wt % PMH nanocomposites are demonstrated cyclic, IR-regulated on/off piezoelectric sensitivity of 889.7, 977.6, and 493.8 mV/(mW·mm-2) at IR powers of 5.3 mW/mm2, respectively. Furthermore, IR self-powered e-skin has been developed successfully and realized an accurate IR stimulus-sensing location due to the sensitivity, which depends on the size of the sensing area. This innovative strategy provides a new route to the fundamental science and applications of flexible IR self-powered devices, such as e-skin, artificial vision, soft robots, active surveillance sensors, etc.

Remineralization effectiveness of the PAMAM dendrimer with different terminal groups on artificial initial enamel caries in vitro.

OBJECTIVE: Disruption of the demineralization-remineralization balance could trigger the development of dental caries, making it challenging for enamel to "self-heal". Thus, extrinsic assistance is needed to restore enamel lesions and stop undermining progression. The aim of this study was to investigate enamel remineralization in a simulated oral environment via poly (amino amine) (PAMAM) dendrimers quantitatively. METHODS: Bovine enamel specimens were shaken in demineralization solution (pH 4.5, 37°C, 50rpm/min) for 72h to create initial enamel carious lesions. The subsurface-demineralized specimens were then divided into four groups: enamel treated with PAMAM-NH2, enamel treated with PAMAM-COOH, enamel treated with PAMAM-OH, and enamel treated with deionized water. The treated specimens underwent subsequent 12-day pH cycling. Enamel blocks were analyzed by transverse microradiography (TMR), surface microhardness testing and scanning electron microscopy (SEM) before and after demineralization and pH cycling. RESULTS: Groups treated with PAMAM dendrimers showed lower lesion depth and less mineral loss, attained more vertical-section surface microhardness recovery, and adsorbed more mineral deposits (p<0.05). The enamel lesion remineralization values of PAMAM-NH2, PAMAM-COOH, and PAMAM-OH groups were 76.42±3.32%, 60.07±5.92% and 54.52±7.81%, respectively. SIGNIFICANCE: In conclusion, PAMAM with different terminal groups could induce enamel remineralization, among which PAMAM-NH2 showed the most prominent competence, followed by PAMAM-COOH and PAMAM-OH, in that order.

Dentin remineralization via adhesive containing amorphous calcium phosphate nanoparticles in a biofilm-challenged environment.

OBJECTIVES: The remineralization of dentin at a bonded interface would help to strengthen the bonded interface and inhibit secondary caries, and would prolong the longevity of restoration. The aim of this study was to investigate the remineralization of demineralized human dentin in a dental biofilm environment via an adhesive containing nanoparticles of amorphous calcium phosphate (NACP). METHODS: Dentin demineralization was promoted by subjecting samples to a Streptococcus mutans acidic biofilm for 24 h. Samples were divided into a control group, a commercial fluoride-releasing adhesive group, and an NACP adhesive group. All samples were subjected to a remineralization protocol consisting of 4-h exposure per 24-h period in brain heart infusion broth plus 1% sucrose (BHIS) followed by immersion in artificial saliva for the remaining period. The pH of BHIS after 4-h immersion was measured every other day. After 10 days, the biofilm was assessed for colony-forming unit (CFU) count, lactic acid production, live/dead staining, and calcium and phosphate content. The mineral changes in the demineralized dentin samples were analyzed by transverse microradiography, hardness measurement, X-ray diffraction characterization, and scanning electron microscopy. RESULTS: The NACP adhesive achieved acid neutralization, decreased biofilm CFU count, decreased biofilm lactic acid production, and increased biofilm calcium and phosphate content (P < 0.05). The NACP adhesive group had higher remineralization value than the commercial fluoride-releasing adhesive group (P < 0.05). CONCLUSIONS: The NACP adhesive was effective in remineralizing dentin lesions in a biofilm model. Its ability to protect bond interface, inhibit secondary caries, and prolong the longevity of restoration is promising. CLINICAL SIGNIFICANCE: Using NACP-containing adhesives could be recommended because of the protective ability of its hybrid layer even under a biofilm-challenged environment.