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To comprehensively describe the operation of photo-induced force microscopy (PiFM), we have developed a model based on coupled harmonic oscillators. This model features two point masses connected by massless elastic wires, offering greater intuitiveness compared to existing PiFM models. It simplifies these models into a unified theoretical framework. By solving the equations of motion using adjusted oscillator parameters, we have successfully replicated all dynamic features from previous theories. These features include resonance frequencies and shapes of eigenmodes, as well as the responses to various external forces in the two PiFM modes: direct coupling and sideband coupling. Furthermore, by integrating our model with a recently developed photo-induced thermal expansion force model, which covers both tip-enhanced and global expansions, we have managed to uncover the underlying physical mechanism responsible for the unique signal behaviors observed in sideband coupling mode, where the signal plot, as a function of sample thickness, unexpectedly exhibits a peak followed by a valley, rather than a proportionally increasing signal. Our study has the potential to enhance the comprehension of various other physical phenomena associated with PiFM in the future.

This study aimed to investigate the impact of plastic particles on cell viability and tissue toxicity. The cells were subjected to incubation with plastic particles immobilized in agar gels, resulting in minimal cell death and cytotoxicity. Furthermore, direct exposure of various cell types to suspended plastic particles showed negligible effects on cell viability, with no observed lysis or growth inhibition. Staining techniques revealed minimal plastic particle‐induced cell death, with the majority of cells remaining viable. However, histological evaluations of mouse tissues demonstrated that the nondegradable low‐density poly(ethylene) (LDPE) groups exhibited severe irritation, characterized by an excessive presence of macrophages, neutrophils, fibrosis, fat infiltration, and increased blood vessel formation in subcutaneous tissue. In contrast, biodegradable neat poly(butylene succinate) (KRICT‐PBS) and cellulose nanocrystals/PBS nanocomposite (CNC‐PBS) groups induced minimal toxicity. Interestingly, the intravenous injection of KRICT‐PBS and CNC‐PBS degradate solutions in mice exhibited mild toxicity, suggesting no significant damage to normal kidney and liver function. [ABSTRACT FROM AUTHOR]

To selectively target and treat murine melanoma B16BL6 tumors expressing αvβ3 integrin receptors, we engineered tumor-specific functional extracellular vesicles (EVs) tailored for the targeted delivery of antitumor drugs. This objective was achieved through the incorporation of a pH-responsive adjuvant, cyclic arginine-glycine-aspartic acid peptide (cRGD, serving as a tumor-targeting ligand), and 5-fluorouracil (5-FU, employed as a model antitumor drug). The pH-responsive adjuvant, essential for modulating drug release, was synthesized by chemically conjugating 3-(diethylamino)propylamine (DEAP) to deoxycholic acid (DOCA, a lipophilic substance capable of integrating into EVs' membranes), denoted as DEAP-DOCA. The DOCA, preactivated using N-(2-aminoethyl)maleimide (AEM), was chemically coupled with the thiol group of the cRGD-DOCA through the thiol–maleimide click reaction, resulting in the formation of cRGD-DOCA. Subsequently, DEAP-DOCA, cRGD-DOCA, and 5-FU were efficiently incorporated into EVs using a sonication method. The resulting tumor-targeting EVs, expressing cRGD ligands, demonstrated enhanced in vitro/in vivo cellular uptake specifically for B16BL6 tumors expressing αvβ3 integrin receptors. The ionization characteristics of the DEAP in DEAP-DOCA induced destabilization of the EVs membrane at pH 6.5 through protonation of the DEAP substance, thereby expediting 5-FU release. Consequently, an improvement in the in vivo antitumor efficacy was observed for B16BL6 tumors. Based on these comprehensive in vitro/in vivo findings, we anticipate that this EV system holds substantial promise as an exceptionally effective platform for antitumor therapeutic delivery. [ABSTRACT FROM AUTHOR]

Transparent, self-healing elastomers play a vital role as protective coatings, particularly in display applications. However, mechanical toughness and efficient self-restoration are often mutually exclusive. A performance equilibrium can be achieved through the molecular design of reversible bonds. However, aromatic disulfide-based dynamic covalent bonds produce an unattractive coloration owing to electron chromophores. In addition, H-bond moieties induce unintended adhesion to the substrates and are limited by hydration-induced weakening. In this study, the molecular design of aliphatic disulfides is presented for colorless, non-tacky, and water-resistant elastomers that rapidly self-heal at ambient temperatures. By employing molecular dynamics simulations, we demonstrate that an excess of H-bond acceptors promotes shorter bond exchange durations while maintaining a higher quantity of cohesive H-bonds, surpassing the performance of equivalent donor/acceptor systems at identical donor concentrations. In addition, dynamic H-bond exchange enables effective healing, whereas the increased H-bond cross-linking density ensures both waterproofness and an impressive tensile strength of 45 MPa. Furthermore, the absence of aromatic groups grants the elastomers a remarkable transmittance of 99%. The optimized properties achieved in this study using the proposed strategic molecular designs will further the commercialization of self-healing thermoplastic polyurethanes as intelligent protective coatings. [ABSTRACT FROM AUTHOR]

In this study, we have developed pH‐dependent nanogels based on hyaluronic acid (HA) to specifically target acidic tumors. Our initial approach involved modifying HA through the grafting of 3‐(diethylamino)propylamine (DEAP), a molecule known for its responsiveness to changes in pH. This modified HA was termed as HDEA. Subsequently, we performed chemical crosslinking of HDEA using adipic acid dihydrazide (ADH), a crosslinking molecule, resulting in the formation of nanogels referred to as cHDEA. Importantly, the non‐ionized DEAP molecules (with a pKb value of ~pH 7.0) at pH 7.4 support the formation of deswellable cHDEA. This property enables the encapsulation of a photodynamic model drug, chlorin e6 (Ce6), into cHDEA. However, when the DEAP molecules become protonated at pH 6.8, they induce a change in the nanogel structure, causing it to swell due to electrostatic repulsion. As a result, Ce6 is rapidly released from the nanogels. By modulating the pH, we can continuously control the nanogel structure, alternating between swelling and deswelling states. We anticipate that this system offers the advantage of facilitating drug release specifically under acidic tumor conditions while inhibiting drug release under normal pH conditions (i.e., pH 7.4). This approach will serve as an effective strategy for mitigating side effects by efficiently controlling drug release in specific disease areas. [ABSTRACT FROM AUTHOR]

In this study, we reported pH‐responsive microparticles consisting of poly(D,L‐lactide‐co‐glycolide) (PLGA), aminated hyaluronic acid (aHA) conjugated with 2,3‐dimethylmaleic anhydride (DMA, as a pH‐responsive cleavable molecule) (aHA‐DMA), and doxorubicin (DOX, as an antitumor drug) for local tumor treatment. The DOX‐loaded microparticles, denoted as PLGA(aHA‐DMA)/DOX MPs, were fabricated using the W1/O/W2 multi‐emulsification method. These PLGA(aHA‐DMA)/DOX MPs (~10 μm in diameter) accelerated the rate of DOX release at pH 6.8 due to the acidic pH‐responsive cleavage of the DMA moieties followed by electrostatic‐repulsion between aHA and DOX. This event caused the structural destabilization and collapse of the MPs, leading to the rapid release of DOX. Consequently, the PLGA(aHA‐DMA)/DOX MPs resulted in significant inhibition of tumor growth, demonstrating their ability for acidic tumor‐specific treatment. [ABSTRACT FROM AUTHOR]