Magnetic-responsive upconversion luminescence resonance energy transfer (LRET) biosensor for ultrasensitive detection of SARS-CoV-2 spike protein

Upconversion nanoparticles (UCNPs) are ideal donors for luminescence resonance energy transfer (LRET)-based biosensors due to their excellent upconversion luminescence properties. However, the relatively large size of antibodies and proteins limits the application of UCNPs-based LRET biosensors in protein detection because the large steric hindrance of proteins leads to low energy transfer efficiency between UCNPs and receptors. Herein, we developed a magnetic responsive UCNPs-based LRET biosensor to control the coupling distance between antibody-functionalized UCNPs (Ab-UCNPs) as donors and antibody-PEG linker-magnetic gold nanoparticles (Ab-PEG-MGNs) as acceptors for ultrasensitive and highly selective detection of SARS-CoV-2 spike proteins. Our results showed that this platform reversibly shortened the coupling distance between UCNPs and MGNs and enhanced the LRET signal with a 10-fold increase in the limit of detection (LOD) from 20.6 pg/mL without magnetic modulation to 2.1 pg/mL with magnetic modulation within 1 h. The finite-difference time-domain (FDTD) simulation with cyclic distance change confirmed the distance-dependent LRET efficiency under magnetic modulation, which supported the experimental results. Moreover, the applications of this magnetic-responsive UCNP-based LRET biosensor could be extended to other large-size biomolecule detection.

Mechanism of Cold Plasma Combined with Glycation in Altering IgE-Binding Capacity and Digestion Stability of Tropomyosin from Shrimp

Tropomyosin (TM) is a major crustacean allergen, and the present studies have tried to reduce its allergenicity by processing technologies. However, most research stopped on the allergenicity and structure of allergens, while information about epitopes was less. In this study, we first investigated the effects of cold plasma (CP) combined with glycation (CP-G) treatment on the processing and trypsin cleavage sites of TM from shrimp (Penaeus chinensis). The results showed a significant reduction in the IgE-binding capacity of TM after CP-G treatment, with a maximum reduction of 30%. This reduction was associated with the combined effects: modification induced by CP destroyed the core helical structure (D137 and E218) and occupied the potential glycation sites, leading to sequent glycation on conserved areas of TM, especially the epitope L130-Q147. Additionally, CP-G treatment decreased the digestion stability of TM by increasing the number of cleavage sites of trypsin and improving the efficiency of some sites, including K5, K6, K30, and R133, resulting in a lower IgE-binding capacity of digestion products, which fell to a maximum of 20%. Thus, CP-G is a valuable and reliable processing technology for the desensitization of aquatic products.

Nanomanipulation of Ligand Nanogeometry Modulates Integrin/Clathrin-Mediated Adhesion and Endocytosis of Stem Cells

Nanosubstrate engineering can be a biomechanical approach for modulating stem cell differentiation in tissue engineering. However, the study of the effect of clathrin-mediated processes on manipulating this behavior is unexplored. Herein, we develop integrin-binding nanosubstrates with confined nanogeometries that regulate clathrin-mediated adhesion- or endocytosis-active signaling pathways for modulating stem fates. Isotropically presenting ligands on the nanoscale enhances the expression of clathrin in cells, thereby facilitating uptake of dexamethasone-loaded nanoparticles (NPs) to boost osteogenesis of stem cells. In contrast, anisotropic ligand nanogeometry suppresses this clathrin-mediated NP entry by strengthening the association between clathrin and adhesion spots to reinforce mechanotransduced signaling, which can be abrogated by the pharmacological inhibition of clathrin. Meanwhile, inhibiting focal adhesion formation hinders cell spreading and enables a higher endocytosis efficiency. Our findings reveal the crucial roles of clathrin in both endocytosis and mechanotransduction of stem cells and provide the parameter of ligand nanogeometry for the rational design of biomaterials for tissue engineering.

Mechanical manipulation of cancer cell tumorigenicity via heat shock protein signaling

Biophysical cues of rigid tumor matrix play a critical role in cancer cell malignancy. We report that stiffly confined cancer cells exhibit robust growth of spheroids in the stiff hydrogel that exerts substantial confining stress on the cells. The stressed condition activated Hsp (heat shock protein)-signal transducer and activator of transcription 3 signaling via the transient receptor potential vanilloid 4-phosphatidylinositol 3-kinase/Akt axis, thereby up-regulating the expression of the stemness-related markers in cancer cells, whereas these signaling activities were suppressed in cancer cells cultured in softer hydrogels or stiff hydrogels with stress relief or Hsp70 knockdown/inhibition. This mechanopriming based on three-dimensional culture enhanced cancer cell tumorigenicity and metastasis in animal models upon transplantation, and pharmaceutically inhibiting Hsp70 improved the anticancer efficacy of chemotherapy. Mechanistically, our study reveals the crucial role of Hsp70 in regulating cancer cell malignancy under mechanically stressed conditions and its impacts on cancer prognosis-related molecular pathways for cancer treatments.

A dual “turn-on” biosensor based on AIE effect and FRET for in situ detection of miR-125b biomarker in early Alzheimer's disease

MicroRNA-125b (miR-125b) is highly associated with synaptic dysfunction and tau hyperphosphorylation in the early pathogenesis of Alzheimer's disease (AD), making it a promising biomarker for early AD diagnosis. Hence, there is an urgent need for a reliable sensing platform to assist in situ miR-125b detection. In this work, we report a dual "turn-on" fluorescence biosensor based on the nanocomposite of aggregation-induced emission fluorogen (AIEgen)-labeled oligonucleotide (TPET-DNA) probes immobilized on the surface of cationic dextran modified molybdenum disulfide (TPET-DNA@Dex-MoS₂). In the presence of the target, TEPT-DNA can hybridize with miR-125b to form a DNA/RNA duplex, causing TPET-DNA to detach from the surface of Dex-MoS₂ that simultaneously activates the dual fluorescence enhancement processes: (1) recovery of TPET-DNA signal and (2) strong fluorescent emission from AIEgen triggered by restriction of the intramolecular rotation. The sensing performance of TPET-DNA@Dex-MoS₂ was demonstrated by detecting miR-125b in vitro with good sensitivity at the picomolar level and rapid response (≤1 h) without amplification procedures. Furthermore, our nanoprobes exhibited excellent imaging capabilities to aid real-time monitoring of the endogenous miR-125b in PC12 cells and brain tissues of mice AD model induced by local administration of okadaic acid (OA). The fluorescence signals of the nanoprobes indicated miR-125b was spatially associated with phosphorylated tau protein (p-tau) in vitro and in vivo. Therefore, TPET-DNA@Dex-MoS₂ could be a promising tool for in situ and real-time monitoring of the AD-related microRNAs and also provide mechanistic insight into the early prognosis of AD.

A Multilayered Mesoporous Gold Nanoarchitecture for Ultraeffective Near-Infrared Light-Controlled Chemo/Photothermal Therapy for Cancer Guided by SERS Imaging

Surface-enhanced Raman scattering (SERS) imaging has emerged as a promising tool for guided cancer diagnosis and synergistic therapies, such as combined chemotherapy and photothermal therapy (chemo-PTT). Yet, existing therapeutic agents often suffer from low SERS sensitivity, insufficient photothermal conversion, or/and limited drug loading capacity. Herein, a multifunctional theragnostic nanoplatform consisting of mesoporous silica-coated gold nanostar with a cyclic Arg-Gly-Asp (RGD)-coated gold nanocluster shell (named RGD-pAS@AuNC) is reported that exhibits multiple "hot spots" for pronouncedly enhanced SERS signals and improved near-infrared (NIR)-induced photothermal conversion efficiency (85.5%), with a large capacity for high doxorubicin (DOX) loading efficiency (34.1%, named RGD/DOX-pAS@AuNC) and effective NIR-triggered DOX release. This nanoplatform shows excellent performance in xenograft tumor model of HeLa cell targeting, negligible cytotoxicity, and good stability both in vitro and in vivo. By SERS imaging, the optimal temporal distribution of injected RGD/DOX-pAS@AuNCs at the tumor site is identified for NIR-triggered local chemo-PTT toward the tumor, achieving ultraeffective therapy in tumor cells and tumor-bearing mouse model with 5 min of NIR irradiation (0.5 W cm^-2 ). This work offers a promising approach to employing SERS imaging for effective noninvasive tumor treatment by on-site triggered chemo-PTT.

Ultraminiature optical fiber-tip directly-printed plasmonic biosensors for label-free biodetection

Miniaturization of biosensors has become an imperative demand because of its great potential in in vivo biomarker detection and disease diagnostics as well as the point-of-care testing for coping with public health crisis, such as the coronavirus disease 2019 pandemic. Here, we present an ultraminiature optical fiber-tip biosensor based on the plasmonic gold nanoparticles (AuNPs) directly printed upon the end face of a standard multimode optical fiber at visible light range. An in-situ precision photoreduction technology is developed to additively print the micropatterns of size-controlled AuNPs. The AuNPs reveal distinct localized surface plasmon resonance, whose peak wavelength provides an ideal spectral signal for label-free biodetection. The fabricated optical fiber-tip plasmonic biosensor can not only detect antibody, but also test SARS-CoV-2 mimetic DNA sequence at the concentration level of 0.8 pM. Such an ultraminiature fiber-tip plasmonic biosensor offers a cost-effective biodetection technology for a myriad of applications ranging from point-of-care testing to in vivo diagnosis of stubborn diseases.

The Effect of the Nanoparticle Shape on T Cell Activation

The mechanism of extracellular ligand nano-geometry in ex vivo T cell activation for immunotherapy remains elusive. Herein, the authors demonstrate large aspect ratio (AR) of gold nanorods (AuNRs) conjugated on cell culture substrate enhancing both murine and human T cell activation through the nanoscale anisotropic presentation of stimulatory ligands (anti-CD3(αCD3) and anti-CD28(αCD28) antibodies). AuNRs with large AR bearing αCD3 and αCD28 antibodies significantly promote T cell expansion and key cytokine secretion including interleukin-2 (IL-2), interferon-gamma (IFN-γ), and tumor necrosis factor-alpha (TNF-α). High membrane tension observed in large AR AuNRs regulates actin filament and focal adhesion assembly and develops maturation-related morphological features in T cells such as membrane ruffle formation, cell spreading, and large T cell receptor (TCR) cluster formation. Anisotropic stimulatory ligand presentation promotes differentiation of naïve CD8⁺ T cells toward the effector phenotype inducing CD137 expression upon co-culture with human cervical carcinoma. The findings suggest the importance of manipulating extracellular ligand nano-geometry in optimizing T cell behaviors to enhance therapeutic outcomes.

A CRISPR-Cas12a integrated SERS nanoplatform with chimeric DNA/RNA hairpin guide for ultrasensitive nucleic acid detection

Background: CRISPR-Cas12a has been integrated with nanomaterial-based optical techniques, such as surface-enhanced Raman scattering (SERS), to formulate a powerful amplification-free nucleic acid detection system. However, nanomaterials impose steric hindrance to limit the accessibility of CRISPR-Cas12a to the narrow gaps (SERS hot spots) among nanoparticles (NPs) for producing a significant change in signals after nucleic acid detection. Methods: To overcome this restriction, we specifically design chimeric DNA/RNA hairpins (displacers) that can be destabilized by activated CRISPR-Cas12a in the presence of target DNA, liberating excessive RNA that can disintegrate a core-satellite nanocluster via toehold-mediated strand displacement for orchestrating a promising "on-off" nucleic acid biosensor. The core-satellite nanocluster comprises a large gold nanoparticle (AuNP) core surrounded by small AuNPs with Raman tags via DNA hybridization as an ultrabright Raman reporter, and its disassembly leads to a drastic decrease of SERS intensity as signal readouts. We further introduce a magnetic core to the large AuNPs that can facilitate their separation from the disassembled nanostructures to suppress the background for improving detection sensitivity. Results: As a proof-of-concept study, our findings showed that the application of displacers was more effective in decreasing the SERS intensity of the system and attained a better limit of detection (LOD, 10 aM) than that by directly using activated CRISPR-Cas12a, with high selectivity and stability for nucleic acid detection. Introducing magnetic-responsive functionality to our system further improves the LOD to 1 aM. Conclusion: Our work not only offers a platform to sensitively and selectively probe nucleic acids without pre-amplification but also provides new insights into the design of the CRISPR-Cas12a/SERS integrated system to resolve the steric hindrance of nanomaterials for constructing biosensors.

An AIEgen/graphene oxide nanocomposite (AIEgen@GO)-based two-stage "turn-on" nucleic acid biosensor for rapid detection of SARS-CoV-2 viral sequence

The ongoing outbreak of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) pandemic has posed significant challenges in early viral diagnosis. Hence, it is urgently desirable to develop a rapid, inexpensive, and sensitive method to aid point-of-care SARS-CoV-2 detection. In this work, we report a highly sequence-specific biosensor based on nanocomposites with aggregation-induced emission luminogens (AIEgen)-labeled oligonucleotide probes on graphene oxide nanosheets (AIEgen@GO) for one step-detection of SARS-CoV-2-specific nucleic acid sequences (Orf1ab or N genes). A dual "turn-on" mechanism based on AIEgen@GO was established for viral nucleic acids detection. Here, the first-stage fluorescence recovery was due to dissociation of the AIEgen from GO surface in the presence of target viral nucleic acid, and the second-stage enhancement of AIE-based fluorescent signal was due to the formation of a nucleic acid duplex to restrict the intramolecular rotation of the AIEgen. Furthermore, the feasibility of our platform for diagnostic application was demonstrated by detecting SARS-CoV-2 virus plasmids containing both Orf1ab and N genes with rapid detection around 1 h and good sensitivity at pM level without amplification. Our platform shows great promise in assisting the initial rapid detection of the SARS-CoV-2 nucleic acid sequence before utilizing quantitative reverse transcription-polymerase chain reaction for second confirmation.

The Interplay Between Epigenetic Regulation and CD8+ T Cell Differentiation/Exhaustion for T Cell Immunotherapy

Effective immunotherapy treats cancers by eradicating tumourigenic cells by activated tumour antigen-specific and bystander CD8⁺ T-cells. However, T-cells can gradually lose cytotoxicity in the tumour microenvironment, known as exhaustion. Recently, DNA methylation, histone modification, and chromatin architecture have provided novel insights into epigenetic regulations of T-cell differentiation/exhaustion, thereby controlling the translational potential of the T-cells. Thus, developing strategies to govern epigenetic switches of T-cells dynamically is critical to maintaining the effector function of antigen-specific T-cells. In this mini-review, we 1) describe the correlation between epigenetic states and T cell phenotypes; 2) discuss the enzymatic factors and intracellular/extracellular microRNA imprinting T-cell epigenomes that drive T-cell exhaustion; 3) highlight recent advances in epigenetic interventions to rescue CD8⁺ T-cell functions from exhaustion. Finally, we express our perspective that regulating the interplay between epigenetic changes and transcriptional programs provides translational implications of current immunotherapy for cancer treatments.

Magnetic-Responsive Surface-Enhanced Raman Scattering Platform with Tunable Hot Spot for Ultrasensitive Virus Nucleic Acid Detection

Surface-enhanced Raman scattering (SERS)-based biosensors are promising tools for virus nucleic acid detection. However, it remains challenging for SERS-based biosensors using a sandwiching strategy to detect long-chain nucleic acids such as nucleocapsid (N) gene of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) because the extension of the coupling distance (CD) between the two tethered metallic nanostructures weakens electric field and SERS signals. Herein, we report a magnetic-responsive substrate consisting of heteoronanostructures that controls the CD for ultrasensitive and highly selective detection of the N gene of SARS-CoV-2. Significantly, our findings show that this platform reversibly shortens the CD and enhances SERS signals with a 10-fold increase in the detection limit from 1 fM to 100 aM, compared to those without magnetic modulation. The optical simulation that emulates the CD shortening process confirms the CD-dependent electric field strength and further supports the experimental results. Our study provides new insights into designing a stimuli-responsive SERS-based platform with tunable hot spots for long-chain nucleic acid detection.

Harnessing Tissue-derived Extracellular Vesicles for Osteoarthritis Theranostics

Osteoarthritis (OA) is a prevalent chronic whole-joint disease characterized by low-grade systemic inflammation, degeneration of joint-related tissues such as articular cartilage, and alteration of bone structures that can eventually lead to disability. Emerging evidence has indicated that synovium or articular cartilage-secreted extracellular vesicles (EVs) contribute to OA pathogenesis and physiology, including transporting and enhancing the production of inflammatory mediators and cartilage degrading proteinases. Bioactive components of EVs are known to play a role in OA include microRNA, long non-coding RNA, and proteins. Thus, OA tissues-derived EVs can be used in combination with advanced nanomaterial-based biosensors for the diagnostic assessment of OA progression. Alternatively, mesenchymal stem cell- or platelet-rich plasma-derived EVs (MSC-EVs or PRP-EVs) have high therapeutic value for treating OA, such as suppressing the inflammatory immune microenvironment, which is often enriched by pro-inflammatory immune cells and cytokines that reduce chondrocytes apoptosis. Moreover, those EVs can be modified or incorporated into biomaterials for enhanced targeting and prolonged retention to treat OA effectively. In this review, we explore recently reported OA-related pathological biomarkers from OA joint tissue-derived EVs and discuss the possibility of current biosensors for detecting EVs and EV-related OA biomarkers. We summarize the applications of MSC-EVs and PRP-EVs and discuss their limitations for cartilage regeneration and alleviating OA symptoms. Additionally, we identify advanced therapeutic strategies, including engineered EVs and applying biomaterials to increase the efficacy of EV-based OA therapies. Finally, we provide our perspective on the future of EV-related diagnosis and therapeutic potential for OA treatment.

Engineering Photoresponsive Ligand Tethers for Mechanical Regulation of Stem Cells

Regulating stem cell functions by precisely controlling the nanoscale presentation of bioactive ligands has a substantial impact on tissue engineering and regenerative medicine but remains a major challenge. Here it is shown that bioactive ligands can become mechanically "invisible" by increasing their tether lengths to the substrate beyond a critical length, providing a way to regulate mechanotransduction without changing the biochemical conditions. Building on this finding, light switchable tethers are rationally designed, whose lengths can be modulated reversibly by switching a light-responsive protein, pdDronpa, in between monomer and dimer states. This allows the regulation of the adhesion, spreading, and differentiation of stem cells by light on substrates of well-defined biochemical and physical properties. Spatiotemporal regulation of differential cell fates on the same substrate is further demonstrated, which may represent an important step toward constructing complex organoids or mini tissues by spatially defining the mechanical cues of the cellular microenvironment with light.

Enhanced mechanosensing of cells in synthetic 3D matrix with controlled biophysical dynamics

3D culture of cells in designer biomaterial matrices provides a biomimetic cellular microenvironment and can yield critical insights into cellular behaviours not available from conventional 2D cultures. Hydrogels with dynamic properties, achieved by incorporating either degradable structural components or reversible dynamic crosslinks, enable efficient cell adaptation of the matrix and support associated cellular functions. Herein we demonstrate that given similar equilibrium binding constants, hydrogels containing dynamic crosslinks with a large dissociation rate constant enable cell force-induced network reorganization, which results in rapid stellate spreading, assembly, mechanosensing, and differentiation of encapsulated stem cells when compared to similar hydrogels containing dynamic crosslinks with a low dissociation rate constant. Furthermore, the static and precise conjugation of cell adhesive ligands to the hydrogel subnetwork connected by such fast-dissociating crosslinks is also required for ultra-rapid stellate spreading (within 18 h post-encapsulation) and enhanced mechanosensing of stem cells in 3D. This work reveals the correlation between microscopic cell behaviours and the molecular level binding kinetics in hydrogel networks. Our findings provide valuable guidance to the design and evaluation of supramolecular biomaterials with cell-adaptable properties for studying cells in 3D cultures.

3D culture systems can provide critical insights into cellular behaviour. Here, the authors study the binding timescale of dynamic crosslinks and the conjugation stability of cell-adhesive ligands in cell–hydrogel network interactions to evaluate the impact on stem cell behaviour, mechanosensing and differentiation.

Manipulation of the Nanoscale Presentation of Integrin Ligand Produces Cancer Cells with Enhanced Stemness and Robust Tumorigenicity

Developing strategies for efficient expansion of cancer stem-like cells (CSCs) in vitro will help investigate the mechanism underlying tumorigenesis and cancer recurrence. Herein, we report a dynamic culture substrate tethered with integrin ligand-bearing magnetic nanoparticles via a flexible polymeric linker to enable magnetic manipulation of the nanoscale ligand tether mobility. The cancer cells cultured on the substrate with high ligand tether mobility develop into large semispherical colonies with CSCs features, which can be abrogated by magnetically restricting the ligand tether mobility. Mechanistically, the substrate with high ligand tether mobility suppresses integrin-mediated mechanotransduction and histone-related methylation, thereby enhancing cancer cell stemness. The culture-derived high-stemness cells can generate tumors both locally and at the distant lung and uterus much more efficiently than the low-stemness cells. We believe that this magnetic nanoplatform provides a promising strategy for investigating the dynamic interaction between CSCs and the microenvironment and establishing a cost-effective tumor spheroid model.

Long-Term Detection of Oncogenic MicroRNA in Living Human Cancer Cells by Gold@ Polydopamine-Shell Nanoprobe

Oncogenic microRNAs (miRNA), for example, miR-155, are key tumor biomarkers in cancer cells that drive tumorigenesis, and the miRNA profile signature can predict cancer development and aggressiveness. Hence, timely detection of oncogenic miRNA in living cells is highly attractive to the diagnosis of cancer at an early stage. Herein, we report a highly sequence-specific gold@polydopamine-based nanoprobe for long-term detection of miRNA in human cancer cell lines in vitro. A single administration of the nanoprobe enables continuous detection of the miR-155 expression level in living cancer cells for up to 5 days. We believe that our nanoprobe is highly promising for both oncology research and translational applications.

Soft Polymeric Matrix as a Macroscopic Cage for Magnetically Modulating Reversible Nanoscale Ligand Presentation

A physical, noninvasive, and reversible means of controlling the nanoscale presentation of bioactive ligands is highly desirable for regulating and investigating the time-dependent responses of cells, including stem cells. Herein we report a magnetically actuated dynamic cell culture platform consisting of a soft hydrogel substrate conjugated with RGD-bearing magnetic nanoparticle (RGD-MNP). The downward/upward magnetic attraction conceals/promotes the presentation of the RGD-MNP in/on the soft hydrogel matrix, thereby inhibiting/enhancing the cell adhesion and mechanosensing-dependent differentiation. Meanwhile, the lateral magnetic attraction promotes the unidirectional migration of cells in the opposite direction on the hydrogel. Furthermore, cyclic switching between the "Exposed" and "Hidden" conditions induces the repeated cycles of differentiation/dedifferentiation of hMSCs which significantly enhances the differentiation potential of hMSCs. Our design approach capitalizes on the bulk biomaterial matrix as the macroscopic caging structure to enable dynamic regulation of cell-matrix interactions reversibly, which is hard to achieve by using conventional cell culture systems.

Biomimetic Presentation of Cryptic Ligands via Single-Chain Nanogels for Synergistic Regulation of Stem Cells

Dynamic controlling the nanoscale presentation of synergistic ligands to stem cells by biomimetic single-chain materials can provide critical insights to understand the molecular crosstalk underlying cells and their extracellular matrix. Here, a stimuli-responsive single-chain macromolecular nanoregulator with conformational dynamics is fabricated based on an advanced scale-up single polymeric chain nanogel (SCNG). Such a carefully designed SCNG is capable of mediating a triggered copresentation of the master and cryptic ligands in a single molecule to elicit the synergistic crosstalk between different intracellular signaling pathways, thereby considerably boosting the bioactivity of the presented ligands. This controllable nanoswitching-on of cell-adhesive ligands' presentation allows the regulation of cell adhesion and fate from molecular scale. The modular nature of this synthetic macromolecular nanoregulator makes it a versatile nanomaterial platform to assist basic and fundamental studies in a wide array of research topics.

Intrapulmonary Cellular-Level Distribution of Inhaled Nanoparticles with Defined Functional Groups and Its Correlations with Protein Corona and Inflammatory Response

Concerns over the health risks associated with airborne exposure to ultrafine particles [PM0.1, or nanoparticles (NPs)] call for a comprehensive understanding in the interactions of inhaled NPs along their respiratory journey. We prepare a collection of polyethylene glycol-coated gold nanoparticles that bear defined functional groups commonly identified in atmospheric particulates (Au@PEG-X NPs, where X = OCH₃, COOH, NH₂, OH, or C₁₂H₂₅). Regardless of the functional group, these ∼50 nm NPs remain colloidally stable following aerosolization and incubation in bronchoalveolar lavage fluid (BALF), without pronouncedly crossing the air-blood barrier. The type of BALF proteins adhered onto the NPs is similar, but the composition of protein corona depends on functional group. By subjecting Balb/c mice to inhalation of Au@PEG-X NPs for 6 h, we demonstrate that the intrapulmonary distribution of NPs among the various types of cells (both found in BALF and isolated from the lavaged lung) and the acute inflammatory responses induced by inhalation are sensitive to the functional group of NPs and postinhalation period (0, 24, or 48 h). By evaluating the pairwise correlations between the three variables of "lung-nano" interactions (protein corona, intrapulmonary cellular-level distribution, and inflammatory response), we reveal strong statistical correlations between the (1) fractions of albumin or carbonyl reductase bound to NPs, (2) associations of inhaled NPs to neutrophils in BALF or macrophages in the lavaged lung, and (3) level of total protein in BALF. Our results provide insights into the effect of functional group on lung-nano interactions and health risks associated with inhalation of PM0.1.

Conformational manipulation of scale-up prepared single-chain polymeric nanogels for multiscale regulation of cells

Folded single chain polymeric nano-objects are the molecular level soft material with ultra-small size. Here, we report an easy and scalable method for preparing single-chain nanogels (SCNGs) with improved efficiency. We further investigate the impact of the dynamic molecular conformational change of SCNGs on cellular interactions from molecular to bulk scale. First, the supramolecular unfoldable SCNGs efficiently deliver siRNAs into stem cells as a molecular drug carrier in a conformation-dependent manner. Furthermore, the conformation changes of SCNGs enable dynamic and precise manipulation of ligand tether structure on 2D biomaterial interfaces to regulate the ligand-receptor ligation and mechanosensing of cells. Lastly, the dynamic SCNGs as the building blocks provide effective energy dissipation to bulk biomaterials such as hydrogels, thereby protecting the encapsulated stem cells from deleterious mechanical shocks in 3D matrix. Such a bottom-up molecular tailoring strategy will inspire further applications of single-chain nano-objects in the biomedical area.

Anisotropic Ligand Nanogeometry Modulates the Adhesion and Polarization State of Macrophages

Material implants trigger host reactions generated by cells, such as macrophages, which display dynamic adhesion and polarization including M1 inflammatory state and M2 anti-inflammatory state. Creating materials that enable diverse nanoscale display of integrin-binding groups, such as RGD ligand, can unravel nanoscale recruitment and ligation of integrin, which modulate cellular adhesion and activation. Here, we synthesized gold nanorods (GNRs) with various nanoscale anisotropies (i.e., aspect ratios, ARs), but in similar surface areas, and controlled their substrate conjugation to display an anisotropic ligand nanogeometry without modulating ligand density. Using nanoscale immunolabeling, we demonstrated that highly anisotropic ligand-coated GNRs ("AR4" and "AR7") facilitated the recruitment of integrin β1 on macrophages to their nanoscale surfaces. Consequently, highly anisotropic GNRs (e.g., "AR4" and "AR7") elevated the adhesion and M2 state of macrophages, with the inhibition of their M1 state in the culture and mice, entailing rho-associated protein kinase. This nanoscale anisotropic nanogeometry provides a novel and critical parameter to be considered in the generation of biomaterials to potentially modulate host reactions to the implants for immunomodulatory tissue regeneration.

Organic Semiconducting Polymer Nanoparticles for Photoacoustic Labeling and Tracking of Stem Cells in the Second Near-Infrared Window

Photoacoustic (PA) imaging and tracking of stem cells plays an important role in the real-time assessment of cell-based therapies. Nevertheless, the limitations of conventional inorganic PA contrast agents and the narrow range of the excitation wavelength in the first near-infrared (NIR-I) window hamper the applications of PA imaging in living subjects. Herein, we report the design and synthesis of a second near-infrared (NIR-II) absorptive organic semiconducting polymer (OSP)-based nanoprobe (OSPN⁺) for PA imaging and tracking of stem cells. Comparison studies in biological tissue show that NIR-II light excited PA imaging of the OSPN⁺ has significantly higher signal-to-noise ratio than NIR-I light excited PA imaging, thereby demonstrating the superiority of the OSPN⁺ for deep tissue imaging. With good biocompatibility, appropriate size, and optimized surface property, the OSPN⁺ shows enhanced cellular uptake for highly efficient PA labeling of stem cells. In vivo investigations reveal significant NIR-II PA contrast enhancement of the transplanted OSPN⁺-labeled human mesenchymal stem cells by 40.6- and 21.7-fold in subcutaneous and brain imaging, respectively, compared with unlabeled cases. Our work demonstrates a class of OSP-based nanomaterials for NIR-II PA stem cell imaging to facilitate a better understanding and evaluation of stem cell-based therapies.