Ortho-oncoplastic surgery in foot and ankle: A narrative overview on reconstruction of soft-tissue defects after oncologic resections

INTRODUCTION

Malignant tumors of the foot are rare, and treatment strategies are challenging considering the complex anatomy of this area. In recent years, dramatic advances in technology and collaborations between different specialties (such as orthopedic, oncology, radiology, plastic, and vascular surgery) significantly changed the approach to complex malignant tumors without resorting to limb removal. The combination of the strengths of both orthopedic surgery and plastic surgery constitutes the modern definition of "orthoplasty." The aim of this review article is to provide treatment strategies that are available for reconstruction of foot and ankle in limb-salvage surgery after tumor resection, with a specific focus on microsurgical techniques in plastic surgery.

METHODS

We conducted a comprehensive search for relevant papers across PubMed, Scopus, Embase, and Web of Science. We included patient-based studies reporting on procedures for soft-tissue reconstruction with small and large soft tissue defects. Indications, pros and cons, and technique tips are discussed for each type of reconstructive technique.

RESULTS

The search was done using literature of the past 30 years (from 1990 to date), resulting in about 725 articles describing over 2000 cases. Cutaneous flaps included lateral supramalleolar flap, medial plantar flap, reverse sural neurocutaneous island flap, medial leg flap, and lateral leg flap. Free flaps included anterolateral thigh flap, radial forearm flap, latissimus dorsi flap, gracilis muscle flap, lateral arm flap, and rectus abdominis flap.

CONCLUSIONS

The orthoplastic approach in musculoskeletal oncology is a collaborative model of orthopedic and plastic surgeons working together, resulting in a higher rate of successful limb salvage in patients at risk for amputation. Protocols, biologic substitutes, and surgical techniques are largely improved in the last decades increasing the possibility of functional reconstruction. Microsurgical strategies represent the new frontiers in these demanding reconstructions.

Pneumonitis After Concurrent Chemoradiation and Immune Checkpoint Inhibition in Patients with Locally Advanced Non-small Cell Lung Cancer

AIMS

Pneumonitis is a common and potentially deadly complication of combined chemoradiation and immune checkpoint inhibition (CRT-ICI) in patients with locally advanced non-small cell lung cancer (LA-NSCLC). In this study we sought to identify the risk factors for pneumonitis with CRT-ICI therapy in LA-NSCLC cases and determine its impact on survival.

MATERIALS AND METHODS

We conducted a retrospective chart review of 140 patients with LA-NSCLC who underwent curative-intent CRT-ICI with durvalumab between 2018 and 2021. Pneumonitis was diagnosed by a multidisciplinary team of clinical experts. We used multivariable cause-specific hazard models to identify risk factors associated with grade ≥2 pneumonitis. We constructed multivariable Cox proportional hazard models to investigate the impact of pneumonitis on all-cause mortality.

RESULTS

The median age of the cohort was 67 years; most patients were current or former smokers (86%). The cumulative incidence of grade ≥2 pneumonitis was 23%. Among survivors, 25/28 patients had persistent parenchymal scarring. In multivariable analyses, the mean lung dose (hazard ratio 1.14 per Gy, 95% confidence interval 1.03-1.25) and interstitial lung disease (hazard ratio 3.8, 95% confidence interval 1.3-11.0) increased the risk for pneumonitis. In adjusted models, grade ≥2 pneumonitis (hazard ratio 2.5, 95% confidence interval 1.0-6.2, P = 0.049) and high-grade (≥3) pneumonitis (hazard ratio 8.3, 95% confidence interval 3.0-23.0, P < 0.001) were associated with higher all-cause mortality.

CONCLUSIONS

Risk factors for pneumonitis in LA-NSCLC patients undergoing CRT-ICI include the mean radiation dose to the lung and pre-treatment interstitial lung disease. Although most cases are not fatal, pneumonitis in this setting is associated with markedly increased mortality.

Large-Scale Functionalized Metasurface-Based SARS-CoV-2 Detection and Quantification

Plasmonic metasurfaces consist of metal-dielectric interfaces that are excitable at background and leakage resonant modes. The sharp and plasmonic excitation profile of metal-free electrons on metasurfaces at the nanoscale can be used for practical applications in diverse fields, including optoelectronics, energy harvesting, and biosensing. Currently, Fano resonant metasurface fabrication processes for biosensor applications are costly, need clean room access, and involve limited small-scale surface areas that are not easy for accurate sample placement. Here, we leverage the large-scale active area with uniform surface patterns present on optical disc-based metasurfaces as a cost-effective method to excite asymmetric plasmonic modes, enabling tunable optical Fano resonance interfacing with a microfluidic channel for multiple target detection in the visible wavelength range. We engineered plasmonic metasurfaces for biosensing through efficient layer-by-layer surface functionalization toward real-time measurement of target binding at the molecular scale. Further, we demonstrated the quantitative detection of antibodies, proteins, and the whole viral particles of SARS-CoV-2 with a high sensitivity and specificity, even distinguishing it from similar RNA viruses such as influenza and MERS. This cost-effective plasmonic metasurface platform offers a small-scale light-manipulation system, presenting considerable potential for fast, real-time detection of SARS-CoV-2 and pathogens in resource-limited settings.

Engineered living bioassemblies for biomedical and functional material applications

Recent breakthroughs in biofabrication of bioasemblies, consisting of the engineered structures composed of biological or biosynthetic components into a single construct, have found a wide range of practical applications in medicine and engineering. This review presents an overview of how the bottom-up assembly of living entities could drive advances in medicine, by developing tunable biological models and more precise methods for quantifying biological events. Moreover, we delve into advances beyond biomedical applications, where bioassemblies can be manipulated as functional robots and construction materials. Finally, we address the potential challenges and opportunities in the field of engineering living bioassemblies, toward building new design principles for the next generation of bioengineering applications.

Acoustic Fabrication of Living Cardiomyocyte-based Hybrid Biorobots

Organized assemblies of cells have demonstrated promise as bioinspired actuators and devices; still, the fabrication of such "biorobots" has predominantly relied on passive assembly methods that reduce design capabilities. To address this, we have developed a strategy for the rapid formation of functional biorobots composed of live cardiomyocytes. We employ tunable acoustic fields to facilitate the efficient aggregation of millions of cells into high-density macroscopic architectures with directed cell orientation and enhanced cell-cell interaction. These biorobots can perform actuation functions both through naturally occurring contraction-relaxation cycles and through external control with chemical and electrical stimuli. We demonstrate that these biorobots can be used to achieve controlled actuation of a soft skeleton and pumping of microparticles. The biocompatible acoustic assembly strategy described here should prove generally useful for cellular manipulation in the context of tissue engineering, soft robotics, and other applications.

Microneedle-mediated Intratumoral Delivery of Anti-CTLA-4 Promotes cDC1-dependent Eradication of Oral Squamous Cell Carcinoma with Limited irAEs

Head and neck squamous cell carcinoma (HNSCC) ranks sixth in cancer incidence worldwide and has a 5-year survival rate of only 63%. Immunotherapies-principally immune checkpoint inhibitors (ICI), such as anti-PD-1 and anti-CTLA-4 antibodies that restore endogenous antitumor T-cell immunity-offer the greatest promise for HNSCC treatment. Anti-PD-1 has been recently approved for first-line treatment of recurrent and metastatic HNSCC; however, less than 20% of patients show clinical benefit and durable responses. In addition, the clinical application of ICI has been limited by immune-related adverse events (irAE) consequent to compromised peripheral immune tolerance. Although irAEs are often reversible, they can become severe, prompting premature therapy termination or becoming life threatening. To address the irAEs inherent to systemic ICI therapy, we developed a novel, local delivery strategy based upon an array of soluble microneedles (MN). Using our recently reported syngeneic, tobacco-signature murine HNSCC model, we found that both systemic and local-MN anti-CTLA-4 therapy lead to >90% tumor response, which is dependent on CD8 T cells and conventional dendritic cell type 1 (cDC1). However, local-MN delivery limited the distribution of anti-CTLA-4 antibody from areas distal to draining lymphatic basins. Employing Foxp3-GFPDTR transgenic mice to interrogate irAEs in vivo, we found that local-MN delivery of anti-CTLA-4 protects animals from irAEs observed with systemic therapy. Taken together, our findings support the exploration of MN-intratumoral ICI delivery as a viable strategy for HNSCC treatment with reduced irAEs, and the opportunity to target cDC1s as part of multimodal treatment options to boost ICI therapy.

High revision rates following repeat septic revision after failed one-stage exchange for periprosthetic joint infection in total knee arthroplasty

AIMS

The outcome of repeat septic revision after a failed one-stage exchange for periprosthetic joint infection (PJI) in total knee arthroplasty (TKA) remains unknown. The aim of this study was to report the infection-free and all-cause revision-free survival of repeat septic revision after a failed one-stage exchange, and to determine whether the Musculoskeletal Infection Society (MSIS) stage is associated with subsequent infection-related failure.

METHODS

We retrospectively reviewed all repeat septic revision TKAs which were undertaken after a failed one-stage exchange between 2004 and 2017. A total of 33 repeat septic revisions (29 one-stage and four two-stage) met the inclusion criteria. The mean follow-up from repeat septic revision was 68.2 months (8.0 months to 16.1 years). The proportion of patients who had a subsequent infection-related failure and all-cause revision was reported and Kaplan-Meier survival for these endpoints was determined. Patients were categorized according to the MSIS staging system, and the association with subsequent infection was analyzed.

RESULTS

At the most recent follow-up, 17 repeat septic revisions (52%) had a subsequent infection-related failure and the five-year infection-free survival was 59% (95% confidence interval (CI) 39 to 74). A total of 19 underwent a subsequent all-cause revision (58%) and the five-year all-cause revision-free survival was 47% (95% CI 28 to 64). The most common indication for the first subsequent aseptic revision was loosening. The MSIS stage of the host status (p = 0.663) and limb status (p = 1.000) were not significantly associated with subsequent infection-related failure.

CONCLUSION

Repeat septic revision after a failed one-stage exchange TKA for PJI is associated with a high rate of subsequent infection-related failure and all-cause revision. Patients should be counselled appropriately to manage expectations. The host and limb status according to the MSIS staging system were not associated with subsequent infection-related failure. Cite this article: Bone Joint J 2022;104-B(3):386-393.

Advanced Point-of-Care Testing Technologies for Human Acute Respiratory Virus Detection

The ever-growing global threats to human life caused by the human acute respiratory virus (RV) infections have cost billions of lives, created a significant economic burden, and shaped society for centuries. The timely response to emerging RVs could save human lives and reduce the medical care burden. The development of RV detection technologies is essential for potentially preventing RV pandemic and epidemics. However, commonly used detection technologies lack sensitivity, specificity, and speed, thus often failing to provide the rapid turnaround times. To address this problem, new technologies are devised to address the performance inadequacies of the traditional methods. These emerging technologies offer improvements in convenience, speed, flexibility, and portability of point-of-care test (POCT). Herein, recent developments in POCT are comprehensively reviewed for eight typical acute respiratory viruses. This review discusses the challenges and opportunities of various recognition and detection strategies and discusses these according to their detection principles, including nucleic acid amplification, optical POCT, electrochemistry, lateral flow assays, microfluidics, enzyme-linked immunosorbent assays, and microarrays. The importance of limits of detection, throughput, portability, and specificity when testing clinical samples in resource-limited settings is emphasized. Finally, the evaluation of commercial POCT kits for both essential RV diagnosis and clinical-oriented practices is included.

Favourable outcomes of repeat one-stage exchange for periprosthetic joint infection of the hip

AIMS

One-stage exchange for periprosthetic joint infection (PJI) in total hip arthroplasty (THA) is gaining popularity. The outcome for a repeat one-stage revision THA after a failed one-stage exchange for infection remains unknown. The aim of this study was to report the infection-free and all-cause revision-free survival of repeat one-stage exchange, and to investigate the association between the Musculoskeletal Infection Society (MSIS) staging system and further infection-related failure.

METHODS

We retrospectively reviewed all repeat one-stage revision THAs performed after failed one-stage exchange THA for infection between January 2008 and December 2016. The final cohort included 32 patients. The mean follow-up after repeat one-stage exchange was 5.3 years (1.2 to 13.0). The patients with a further infection-related failure and/or all-cause revision were reported, and Kaplan-Meier survival for these endpoints determined. Patients were categorized according to the MSIS system, and its association with further infection was analyzed.

RESULTS

A total of eight repeat septic revisions (25%) developed a further infection-related failure, and the five-year infection-free survival was 81% (95% confidence interval (CI) 57 to 92). Nine (28%) underwent a further all-cause revision and the five-year all-cause revision-free survival was 74% (95% CI 52 to 88). Neither the MSIS classification of the host status (p = 0.423) nor the limb status (p = 0.366) was significantly associated with further infection-related failure.

CONCLUSION

Repeat one-stage exchange for PJI in THA is associated with a favourable five-year infection-free and all-cause revision-free survival. Notably, the rate of infection control is encouraging when compared with the reported rates after repeat two-stage exchange. The results can be used to counsel patients and help clinicians make informed decisions about treatment. With the available number of patients, further infection-related failure was not associated with the MSIS host or limb status. Cite this article: Bone Joint J 2022;104-B(1):27-33.

I've got you under my skin: inflammatory response to elephant seal's lice

Seals (Phocidae) undergo an annual cycle of moulting that implies hair regeneration, and in the case of southern elephant seals, it also involves the superficial strata of the epidermis. Therefore, surviving the moulting period is crucial for their obligate and permanent ectoparasites. Throughout evolutionary time, sucking lice (Echinophtiriidae) have developed morphological, behavioural and ecological adaptations to cope with the amphibious lifestyle of their hosts. Lepidophthirus macrorhini, the Southern elephant seal louse species, faces the additional challenge of surviving attached to the host during the moulting period. Since lice live on the skin, L. macrorhini has developed a unique survival strategy by piercing the skin of their host, thus keeping them protected from moulting. During fieldwork in Patagonia and Antarctica, skin samples with lice within were collected for histological analysis to assess whether these parasites caused damage to the host. Lice generate an inflammatory process in the host's dermis, and these lesions could alter the normal chemical and mechanical protective properties of the skin facilitating secondary infections. Further studies that analyse the potential pathogens in those skin lesions are necessary to properly assess the real impact of ectoparasites on their host health.

Engineering Polysaccharide-Based Hydrogel Photonic Constructs: From Multiscale Detection to the Biofabrication of Living Optical Fibers

Solid-state optics has been the pillar of modern digital age. Integrating soft hydrogel materials with micro/nanooptics could expand the horizons of photonics for bioengineering. Here, wet-spun multilayer hydrogel fibers are engineered through ionic-crosslinked natural polysaccharides that serve as multifunctional platforms. The resulting flexible hydrogel structure and reversible crosslinking provide tunable design properties such as adjustable refractive index and fusion splicing. Modulation of the optical readout via physical stimuli, including shape, compression, and multiple optical inputs/outputs is demonstrated. The unique permeability of the hydrogels is also combined with plasmonic nanoparticles for molecular detection of SARS-CoV-2 in fiber-coupled biomedical swabs. A tricoaxial 3D printing nozzle is then employed for the continuous fabrication of living optical fibers. Light interaction with living cells enables the quantification and digitalization of complex biological phenomena such as 3D cancer progression and drug susceptibility. These fibers pave the way for advances in biomaterial-based photonics and biosensing platforms.

Risk Factors Associated With Bronchiolitis in Puerto Rican Children

OBJECTIVE

The objective of this study was to identify frequency, severity, and risk factors associated with bronchiolitis in Puerto Rican children.

METHODS

A cross-sectional was study performed at 4 emergency departments of Puerto Rico's metropolitan area, between June 2014 and May 2015. We included children younger than 24 months, with a clinical diagnosis of bronchiolitis, who were born and living in Puerto Rico at the time of recruitment. A physician-administered questionnaire inquiring about the patient's medical, family, and social history and a bronchiolitis severity assessment were performed. Daily weather conditions were monitored, and aeroallergens were collected with an air sample and precision weather station within the metropolitan area to evaluate environmental factors.

RESULTS

We included 600 patients for 12 months. More than 50% of the recruited patients had a previous episode of bronchiolitis, of which 40% had been hospitalized. Older age (odds ratio [OR], 18.3; 95% confidence interval [CI], 9.2-36.5), male sex (OR, 1.6; 95% CI, 1.1-2.4), history of asthma (OR, 8.9; 95% CI, 3.6-22), allergic rhinitis (OR, 3.6; 95% CI, 1.8-7.4), and smoke exposure by a caretaker (OR, 2.3; 95% CI, 1.2-4.4) were predictors of bronchiolitis episodes. Bronchiolitis episodes were associated with higher severity score (P = 0.040), increased number of atopic factors (P < 0.001), and higher number of hospitalizations (P < 0.001).

CONCLUSIONS

This study identifies Puerto Rican children who may present a severe clinical course of disease without traditional risk factors. Atopy-related factors are associated with frequency and severity of bronchiolitis. Puerto Rican children present risk factors related to atopy earlier in life, some of which may be modified to prevent the subsequent development of asthma.

Wearable Collector for Noninvasive Sampling of SARS-CoV-2 from Exhaled Breath for Rapid Detection

Airborne transmission of exhaled virus can rapidly spread, thereby increasing disease progression from local incidents to pandemics. Due to the COVID-19 pandemic, states and local governments have enforced the use of protective masks in public and work areas to minimize the disease spread. Here, we have leveraged the function of protective face coverings toward COVID-19 diagnosis. We developed a user-friendly, affordable, and wearable collector. This noninvasive platform is integrated into protective masks toward collecting airborne virus in the exhaled breath over the wearing period. A viral sample was sprayed into the collector to model airborne dispersion, and then the enriched pathogen was extracted from the collector for further analytical evaluation. To validate this design, qualitative colorimetric loop-mediated isothermal amplification, quantitative reverse transcription polymerase chain reaction, and antibody-based dot blot assays were performed to detect the presence of SARS-CoV-2. We envision that this platform will facilitate sampling of current SARS-CoV-2 and is potentially broadly applicable to other airborne diseases for future emerging pandemics.

Designer exosomes enabling tumor targeted efficient chemo/gene/photothermal therapy

Exosomes, endogenous nanosized particles (50-150 nm) secreted and absorbed by cells, have been recently used as diagnostic and therapeutic platforms in cancer treatment. The integration of exosome-based delivery with multiple therapeutic modalities could result in better clinical outcomes and reduced-sided effects. Here, we combined the targeting and biocompatibility of designer exosomes with chemo/gene/photothermal therapy. Our platform consists of exosomes loaded with internalized doxorubicin (DOX, a model cancer drug) and coated with magnetic nanoparticles conjugated with molecular beacons capable of targeting miR-21 for responsive molecular imaging. The coated magnetic nanoparticle enables enrichment of the exosomes at the tumor site by external magnetic field guidance. After the exosomes are gathered at the tumor site, the application of near-infrared radiation (NIR) induces localized hyperthermia and triggers the release of cargoes loaded inside the exosome. The released molecular beacon can target the miR-21 for both imaging and gene silencing. Meanwhile, the released doxorubicin serves to kill the cancer cells. About 91.04 % of cancer cells are killed after treatment with Exo-DOX-Fe₃O₄@PDA-MB under NIR. The ability of the exosome-based method for cancer therapy has been demonstrated by animal models, in which the tumor size is reduced dramatically by 97.57 % with a magnetic field-guided tumor-targeted chemo/gene/photothermal approach. Thus, we expected this designer exosome-mediated multi-mode therapy to be a promising platform for the next-generation precision cancer nanomedicines.

Reversible Design of Dynamic Assemblies at Small Scales

Emerging bottom-up fabrication methods have enabled the assembly of synthetic colloids, microrobots, living cells, and organoids to create intricate structures with unique properties that transcend their individual components. This review provides an access point to the latest developments in externally driven assembly of synthetic and biological components. In particular, we emphasize reversibility, which enables the fabrication of multiscale systems that would not be possible under traditional techniques. Magnetic, acoustic, optical, and electric fields are the most promising methods for controlling the reversible assembly of biological and synthetic subunits since they can reprogram their assembly by switching on/off the external field or shaping these fields. We feature capabilities to dynamically actuate the assembly configuration by modulating the properties of the external stimuli, including frequency and amplitude. We describe the design principles which enable the assembly of reconfigurable structures. Finally, we foresee that the high degree of control capabilities offered by externally driven assembly will enable broad access to increasingly robust design principles towards building advanced dynamic intelligent systems.

Combinatorial microneedle patch with tunable release kinetics and dual fast-deep/sustained release capabilities

Transdermal microneedle (MN) drug delivery patches, comprising water-soluble polymers, have played an essential role in diverse biomedical applications, but with limited development towards fast deep release or sustained delivery applications. The effectiveness of such MN delivery patches strongly depends on the materials from which they are constructed. Herein, we present a dual-action combinatorial programmable MN patch, comprising of fast and sustained-release MN zones, with tunable release kinetics towards delivering a wide range of therapeutics over different timeframes in single application. We demonstrate the fine tuning of MN materials; the patches can be tailored to deliver a first payload faster and deeper within minutes, while simultaneously delivering a second payload over long times ranging from weeks to months. The active and rapid burst release relies on embedding biodegradable Mg microparticle 'engines' in dissolvable MNs while the sustained release is attributed to biocompatible polymers that allow prolonged release in a controllable tunable manner. In addition, the patches are characterized and optimized for their design, materials and mechanical properties. These studies indicate that such programmable dual-action versatile MN platform is expected to improve therapeutic efficacy and patient compliance, achieving powerful benefits by single patch application at low manufacturing cost.

Emerging biofabrication approaches for gastrointestinal organoids towards patient specific cancer models

Tissue engineered organoids are simple biomodels that can emulate the structural and functional complexity of specific organs. Here, we review developments in three-dimensional (3D) artificial cell constructs to model gastrointestinal dynamics towards cancer diagnosis. We describe bottom-up approaches to fabricate close-packed cell aggregates, from the use of biochemical and physical cues to guide the self-assembly of organoids, to the use of engineering approaches, including 3D printing/additive manufacturing and external field-driven protocols. Finally, we outline the main challenges and possible risks regarding the potential translation of gastrointestinal organoids from laboratory settings to patient-specific models in clinical applications.

Hybrid biomembrane-functionalized nanorobots for concurrent removal of pathogenic bacteria and toxins

With the rapid advancement of robotic research, it becomes increasingly interesting and important to develop biomimetic micro- or nanorobots that translate biological principles into robotic systems. We report the design, construction, and evaluation of a dual-cell membrane-functionalized nanorobot for multipurpose removal of biological threat agents, particularly concurrent targeting and neutralization of pathogenic bacteria and toxins. Specifically, we demonstrated ultrasound-propelled biomimetic nanorobots consisting of gold nanowires cloaked with a hybrid of red blood cell (RBC) membranes and platelet (PL) membranes. Such hybrid cell membranes have a variety of functional proteins associated with human RBCs and PLs, which give the nanorobots a number of attractive biological capabilities, including adhesion and binding to PL-adhering pathogens (e.g., Staphylococcus aureus bacteria) and neutralization of pore-forming toxins (e.g., α-toxin). In addition, the biomimetic nanorobots displayed rapid and efficient prolonged acoustic propulsion in whole blood, with no apparent biofouling, and mimicked the movement of natural motile cells. This propulsion enhanced the binding and detoxification efficiency of the robots against pathogens and toxins. Overall, coupling these diverse biological functions of hybrid cell membranes with the fuel-free propulsion of the nanorobots resulted in a dynamic robotic system for efficient isolation and simultaneous removal of different biological threats, an important step toward the creation of a broad-spectrum detoxification robotic platform.

Engineering the Interaction Dynamics between Nano-Topographical Immunocyte-Templated Micromotors across Scales from Ions to Cells

Manufacturing mobile artificial micromotors with structural design factors, such as morphology nanoroughness and surface chemistry, can improve the capture efficiency through enhancing contact interactions with their surrounding targets. Understanding the interplay of such parameters targeting high locomotion performance and high capture efficiency at the same time is of paramount importance, yet, has so far been overlooked. Here, an immunocyte-templated nano-topographical micromotor is engineered and their interactions with various targets across multiple scales, from ions to cells are investigated. The macrophage templated nanorough micromotor demonstrates significantly increased surface interactions and significantly improved and highly efficient removal of targets from complex aqueous solutions, including in plasma and diluted blood, when compared to smooth synthetic material templated micromotors with the same size and surface chemistry. These results suggest that the surface nanoroughness of the micromotors for the locomotion performance and interactions with the multiscale targets should be considered simultaneously, for they are highly interconnected in design considerations impacting applications across scales.

Medical Micro/Nanorobots in Precision Medicine

Advances in medical robots promise to improve modern medicine and the quality of life. Miniaturization of these robotic platforms has led to numerous applications that leverages precision medicine. In this review, the current trends of medical micro and nanorobotics for therapy, surgery, diagnosis, and medical imaging are discussed. The use of micro and nanorobots in precision medicine still faces technical, regulatory, and market challenges for their widespread use in clinical settings. Nevertheless, recent translations from proof of concept to in vivo studies demonstrate their potential toward precision medicine.

Built-In Active Microneedle Patch with Enhanced Autonomous Drug Delivery

The use of microneedles has facilitated the painless localized delivery of drugs across the skin. However, their efficacy has been limited by slow diffusion of molecules and often requires external triggers. Herein, an autonomous and degradable, active microneedle delivery platform is introduced, employing magnesium microparticles loaded within the microneedle patch, as the built-in engine for deeper and faster intradermal payload delivery. The magnesium particles react with the interstitial fluid, leading to an explosive-like rapid production of H2 bubbles, providing the necessary force to breach dermal barriers and enhance payload delivery. The release kinetics of active microneedles is evaluated in vitro by measuring the amount of IgG antibody (as a model drug) that passed through phantom tissue and a pigskin barrier. In vivo experiments using a B16F10 mouse melanoma model demonstrate that the active delivery of anti-CTLA-4 (a checkpoint inhibitor drug) results in greatly enhanced immune response and significantly longer survival. Moreover, spatially resolved zones of active and passive microneedles allow a combinatorial rapid burst response along with slow, sustained release, respectively. Such versatile and effective autonomous dynamic microneedle delivery technology offers considerable promise for a wide range of therapeutic applications, toward a greatly enhanced outcome, convenience, and cost.

Multigear Bubble Propulsion of Transient Micromotors

Transient, chemically powered micromotors are promising biocompatible engines for microrobots. We propose a framework to investigate in detail the dynamics and the underlying mechanisms of bubble propulsion for transient chemically powered micromotors. Our observations on the variations of the micromotor active material and geometry over its lifetime, from initial activation to the final inactive state, indicate different bubble growth and ejection mechanisms that occur stochastically, resulting in time-varying micromotor velocity. We identify three processes of bubble growth and ejection, and in analogy with macroscopic multigear machines, we call each process a gear. Gear 1 refers to bubbles that grow on the micromotor surface before detachment while in Gear 2 bubbles hop out of the micromotor. Gear 3 is similar in nature to Gear 2, but the bubbles are too small to contribute to micromotor motion. We study the characteristics of these gears in terms of bubble size and ejection time, and how they contribute to micromotor displacement. The ability to tailor the shell polarity and hence the bubble growth and ejection and the surrounding fluid flow is demonstrated. Such understanding of the complex multigear bubble propulsion of transient chemical micromotors should guide their future design principles and serve for fine tuning the performance of these micromotors.

3D steerable, acoustically powered microswimmers for single-particle manipulation

The ability to precisely maneuver micro/nano objects in fluids in a contactless, biocompatible manner can enable innovative technologies and may have far-reaching impact in fields such as biology, chemical engineering, and nanotechnology. Here, we report a design for acoustically powered bubble-based microswimmers that are capable of autonomous motion in three dimensions and selectively transporting individual synthetic colloids and mammalian cells in a crowded group without labeling, surface modification, or effect on nearby objects. In contrast to previously reported microswimmers, their motion does not require operation at acoustic pressure nodes, enabling propulsion at low power and far from an ultrasonic transducer. In a megahertz acoustic field, the microswimmers are subject to two predominant forces: the secondary Bjerknes force and a locally generated acoustic streaming propulsive force. The combination of these two forces enables the microswimmers to independently swim on three dimensional boundaries or in free space under magnetical steering.

Noninvasive Transdermal Delivery System of Lidocaine Using an Acoustic Droplet-Vaporization Based Wearable Patch

Current technologies for managing acute and chronic pain have focused on reducing the time required for achieving high therapeutic efficiency. Herein a wearable transdermal patch is introduced, employing an acoustic droplet vaporization (ADV) methodology, as an effective noninvasive transdermal platform, for a fast local delivery of the anesthetic agent lidocaine. The skin-worn patch consists of a flexible drug reservoir containing hundreds of micropores loaded with lidocaine, and mixed with the perfluorocarbon (PFC) emulsion. The ultrasound-triggered vaporization of the PFC emulsion provides the necessary force to breach dermal barriers. The drug release kinetics of our model was investigated by measuring the amount of lidocaine that passed through phantom tissue and pigskin barriers. The ADV platform increases the payload skin penetration resulting in shorter treatment times compared to passive diffusion or ultrasound alone, holding considerable promise for addressing the delayed therapeutic action and slow pain relief of existing delivery protocols. It is envisioned that the integration of ADV-based transdermal devices could be expanded to the depth-dependent delivery of other pain management, vaccines, and gene therapy modalities.

Frontiers of Medical Micro/Nanorobotics: in vivo Applications and Commercialization Perspectives Toward Clinical Uses

The field of medical micro/nanorobotics holds considerable promise for advancing medical diagnosis and treatment due to their unique ability to move and perform complex task at small scales. Nevertheless, the grand challenge of the field remains in its successful translation towards widespread patient use. We critically address the frontiers of the current methodologies for in vivo applications and discuss the current and foreseeable perspectives of their commercialization. Although no "killer application" that would catalyze rapid commercialization has yet emerged, recent engineering breakthroughs have led to the successful in vivo operation of medical micro/nanorobots. We also highlight how standardizing report summaries of micro/nanorobotics is essential not only for increasing the quality of research but also for minimizing investment risk in their potential commercialization. We review current patents and commercialization efforts based on emerging proof-of-concept applications. We expect to inspire future research efforts in the field of micro/nanorobotics toward future medical diagnosis and treatment.

Bartonella vinsonii subsp. berkhoffii and B. henselae in dogs

This study aimed to molecularly survey Bartonella in dogs from Chile. Quantitative real-time PCR (qPCR) for Bartonella spp. based on nuoG gene was performed in 139 blood samples taken from dogs belonging to rural localities of the Valdivia Province, Los Ríos region, southern Chile. nuoG qPCR-positive samples were submitted to conventional PCR assays for ftsZ, gltA, rpoB and nuoG genes and sequencing for speciation and phylogenetic analysis. Based upon qPCR results, Bartonella spp. occurrence in dogs was 4.3% (6/139). Out of six nuoG qPCR-positive samples, six, three, two and none showed positive results in cPCR assays based on gltA, ftsZ, rpoB and nuoG genes, respectively. Consistent sequencing results were obtained only for the ftsZ gene from sample #1532 (GeneBank accession number: MG252491), and gltA gene from samples #1535 (MG252490) and #1532 (148 bp fragment that was not deposited in GenBank). Phylogenetic analysis of ftsZ and gltA genes allowed speciation of two nuoG-positive samples, one as Bartonella vinsonii subsp. berkhoffii and the other as B. henselae. Bartonella vinsonii subsp. berkhoffii and B. henselae are detected for the first time in dogs from Chile, highlighting the importance of the canine population as a source of zoonotic agents and potential infection risk to humans.

Topographical Manipulation of Microparticles and Cells with Acoustic Microstreaming

Precise and reproducible manipulation of synthetic and biological microscale objects in complex environments is essential for many practical biochip and microfluidic applications. Here, we present an attractive acoustic topographical manipulation (ATM) method to achieve efficient and reproducible manipulation of diverse microscale objects. This new guidance method relies on the acoustically induced localized microstreaming forces generated around microstructures, which are capable of trapping nearby microobjects and manipulating them along a determined trajectory based on local topographic features. This unique phenomenon is investigated by numerical simulations examining the local microstreaming in the presence of microscale boundaries under the standing acoustic wave. This method can be used to manipulate a single microobject around a complex structure as well as collectively manipulate multiple objects moving synchronously along complicated shapes. Furthermore, the ATM can serve for automated maze solving by autonomously manipulating microparticles with diverse geometries and densities, including live cells, through complex maze-like topographical features without external feedback, particle modification, or adjustment of operational parameters.

A microneedle biosensor for minimally-invasive transdermal detection of nerve agents

A microneedle array based biosensor for minimally invasive electrochemical monitoring of organophosphate (OP) nerve agents under the skin.

Transient Micromotors That Disappear When No Longer Needed

Transient self-destroyed micromotors that autonomously disappear in biological media at controlled rates upon completing their task, without leaving a toxic residue, are presented. The propulsion and degradation characteristics of the self-destroyed Mg/ZnO, Mg/Si, and Zn/Fe Janus micromotors and single-component Zn micromotors are described. The degradation of the Janus micromotors relies on the different corrosion rates of their core-shell components. Inductively coupled plasma optical emission spectrometry measurements are used to probe the time-dependent degradation of the different constituents of the micromotors. The toxicity of the transient micromotors is discussed toward their potential use in biomedical applications. This concept of transient micromotors offers considerable potential for diverse practical applications in the near future.

Enteric Micromotor Can Selectively Position and Spontaneously Propel in the Gastrointestinal Tract

The gastrointestinal (GI) tract, which hosts hundreds of bacteria species, becomes the most exciting organ for the emerging microbiome research. Some of these GI microbes are hostile and cause a variety of diseases. These bacteria colonize in different segments of the GI tract dependent on the local physicochemical and biological factors. Therefore, selectively locating therapeutic or imaging agents to specific GI segments is of significant importance for studying gut microbiome and treating various GI-related diseases. Herein, we demonstrate an enteric micromotor system capable of precise positioning and controllable retention in desired segments of the GI tract. These motors, consisting of magnesium-based tubular micromotors coated with an enteric polymer layer, act as a robust nanobiotechnology tool for site-specific GI delivery. The micromotors can deliver payload to a particular location via dissolution of their enteric coating to activate their propulsion at the target site toward localized tissue penetration and retention.

Acoustically propelled nanoshells

Herein we report a new design for acoustic nanoswimmers, making use of a nanoshell geometry that was synthesized using a sphere template process. Such shell-shaped nanomotors display highly efficient acoustic propulsion on the nanoscale by converting energy from the ambient acoustic field into motion. The propulsion mechanism of the nanoshell motors relies on acoustic streaming stress over the asymmetric surface to produce the driving force for motion. The shell-shaped nanomotors offer a high surface area to volume ratio, allow for efficient scalability and provide higher cargo towing capacity (in comparison to acoustically propelled nanowires). Furthermore, a detailed study of the parameters relevant to propulsion performance, including the material density, size and shape of the motors, reveals that the nanoshell motors exhibit a different propulsion behavior from that predicted by recent theoretical and experimental models for acoustically propelled nanomotors. Such findings indicate that further studies are needed to predict the behavior of acoustic nanomotors with different geometry designs. Practical applications of the new nanoshell motors, including "on-the-move" capture and the transport of multiple cargoes and internalization and movement inside live MCF-7 cancer cells, are demonstrated. These capabilities hold considerable promise for designing fuel-free nanoswimmers capable of performing complex tasks for diverse biomedical applications.

Acoustically Propelled Nanomotors for Intracellular siRNA Delivery

An effective intracellular gene silencing strategy based on acoustically propelled nanowires modified with an interfering RNA's (siRNA) payload is described. The gold nanowires (AuNW) are wrapped with a Rolling Circle Amplification (RCA) DNA strand, which serves to anchor the siRNA therapy. The ultrasound (US)-powered propulsion of the AuNW leads to fast internalization and rapid intracellular movement and hence to an accelerated siRNA delivery and silencing response. To optimize the micromotor gene silencing procedure, the influence of motion, time, and siRNA dosage was investigated, leading up to a 94% silencing after few minutes treatment with US-propelled siRNA-AuNWs, and to a dramatic (∼13-fold) improvement in the silencing response compared to the static modified nanowires. The ability of the nanomotor-based method for gene silencing has been demonstrated by measuring the GFP silencing response in two different cell lines (HEK-293 and MCF-7) and using detailed control experiments. The viability of the cells after the nanomotors treatment was examined using the MCF-7 cancer cell line. The use of DNA structures carried by the US-propelled nanomotors for gene silencing represents an efficient tool that addresses the challenges associated with RNA transportation and intracellular delivery. Future implementation of nanomachines in gene therapy applications can be expanded into a co-delivery platform for therapeutics.

Acoustic Microcannons: Toward Advanced Microballistics

Acoustically triggered microcannons, capable of loading and firing nanobullets (Nbs), are presented as powerful microballistic tools. Hollow conically shaped microcannon structures have been synthesized electrochemically and fully loaded with nanobullets made of silica or fluorescent microspheres, and perfluorocarbon emulsions, embedded in a gel matrix stabilizer. Application of a focused ultrasound pulse leads to the spontaneous vaporization of the perfluorocarbon emulsions within the microcannon and results in the rapid ejection of the nanobullets. Such Nbs "firing" at remarkably high speeds (on the magnitude of meters per second) has been modeled theoretically and demonstrated experimentally. Arrays of microcannons anchored in a template membrane were used to demonstrate the efficient Nbs loading and the high penetration capabilities of the ejected Nbs in a tissue phantom gel. This acoustic-microcannon approach could be translated into advanced microscale ballistic tools, capable of efficient loading and firing of multiple cargoes, and offer improved accessibility to target locations and enhanced tissue penetration properties.

Delayed ignition and propulsion of catalytic microrockets based on fuel-induced chemical dealloying of the inner alloy layer

The delayed ignition of catalytic microrockets based on chemical dealloying of an inner alloy layer is demonstrated.

Lysozyme-Based Antibacterial Nanomotors

An effective and rapid bacterial killing nanotechnology strategy based on lysozyme-modified fuel-free nanomotors is demonstrated. The efficient antibacterial property of lysozyme, associated with the cleavage of glycosidic bonds of peptidoglycans present in the bacteria cell wall, has been combined with ultrasound (US)-propelled porous gold nanowire (p-AuNW) motors as biocompatible dynamic bacteria nanofighters. Coupling the antibacterial activity of the enzyme with the rapid movement of these p-AuNWs, along with the corresponding fluid dynamics, promotes enzyme-bacteria interactions and prevents surface aggregation of dead bacteria, resulting in a greatly enhanced bacteria-killing capability. The large active surface area of these nanoporous motors offers a significantly higher enzyme loading capacity compared to nonporous AuNWs, which results in a higher antimicrobial activity against Gram-positive and Gram-negative bacteria. Detailed characterization studies and control experiments provide useful insights into the underlying factors controlling the antibacterial performance of the new dynamic bacteria nanofighters. Rapid and effective killing of the Gram-positive Micrococcus lysodeikticus bacteria (69-84% within 1-5 min) is demonstrated.

Single Cell Real-Time miRNAs Sensing Based on Nanomotors

A nanomotor-based strategy for rapid single-step intracellular biosensing of a target miRNA, expressed in intact cancer cells, at the single cell level is described. The new concept relies on the use of ultrasound (US) propelled dye-labeled single-stranded DNA (ssDNA)/graphene-oxide (GO) coated gold nanowires (AuNWs) capable of penetrating intact cancer cells. Once the nanomotor is internalized into the cell, the quenched fluorescence signal (produced by the π-π interaction between GO and a dye-labeled ssDNA) is recovered due to the displacement of the dye-ssDNA probe from the motor GO-quenching surface upon binding with the target miRNA-21, leading to an attractive intracellular "OFF-ON" fluorescence switching. The faster internalization process of the US-powered nanomotors and their rapid movement into the cells increase the likelihood of probe-target contacts, leading to a highly efficient and rapid hybridization. The ability of the nanomotor-based method to screen cancer cells based on the endogenous content of the target miRNA has been demonstrated by measuring the fluorescence signal in two types of cancer cells (MCF-7 and HeLa) with significantly different miRNA-21 expression levels. This single-step, motor-based miRNAs sensing approach enables rapid "on the move" specific detection of the target miRNA-21, even in single cells with an extremely low endogenous miRNA-21 content, allowing precise and real-time monitoring of intracellular miRNA expression.

Reversible swarming and separation of self-propelled chemically powered nanomotors under acoustic fields

The collective behavior of biological systems has inspired efforts toward the controlled assembly of synthetic nanomotors. Here we demonstrate the use of acoustic fields to induce reversible assembly of catalytic nanomotors, controlled swarm movement, and separation of different nanomotors. The swarming mechanism relies on the interaction between individual nanomotors and the acoustic field, which triggers rapid migration and assembly around the nearest pressure node. Such on-demand assembly of catalytic nanomotors is extremely fast and reversible. Controlled movement of the resulting swarm is illustrated by changing the frequency of the acoustic field. Efficient separation of different types of nanomotors, which assemble in distinct swarming regions, is illustrated. The ability of acoustic fields to regulate the collective behavior of catalytic nanomotors holds considerable promise for a wide range of practical applications.

Self-propelled screen-printable catalytic swimmers

A highly versatile 2D screen-printing fabrication of nature-inspired fish swimmers is described.

Ultrasound-propelled nanoporous gold wire for efficient drug loading and release

Ultrasound (US)-powered nanowire motors based on nanoporous gold segment are developed for increasing the drug loading capacity. The new highly porous nanomotors are characterized with a tunable pore size, high surface area, and high capacity for the drug payload. These nanowire motors are prepared by template membrane deposition of a silver-gold alloy segment followed by dealloying the silver component. The drug doxorubicin (DOX) is loaded within the nanopores via electrostatic interactions with an anionic polymeric coating. The nanoporous gold structure also facilitates the near-infrared (NIR) light controlled release of the drug through photothermal effects. Ultrasound-driven transport of the loaded drug toward cancer cells followed by NIR-light triggered release is illustrated. The incorporation of the nanoporous gold segment leads to a nearly 20-fold increase in the active surface area compared to common gold nanowire motors. It is envisioned that such US-powered nanomotors could provide a new approach to rapidly and efficiently deliver large therapeutic payloads in a target-specific manner.

Functionalized ultrasound-propelled magnetically guided nanomotors: toward practical biomedical applications

Magnetically guided ultrasound-powered nanowire motors, functionalized with bioreceptors and a drug-loaded polymeric segment, are described for "capture and transport" and drug-delivery processes. These high-performance fuel-free motors display advanced capabilities and functionalities, including magnetic guidance, coordinated aligned movement, cargo towing, capture and isolation of biological targets, drug delivery, and operation in real-life biological and environmental media. The template-prepared three-segment Au-Ni-Au nanowire motors are propelled acoustically by mechanical waves produced by a piezoelectric transducer. An embedded nickel segment facilitates a magnetically guided motion as well as transport of large "cargo" along predetermined trajectories. Substantial improvement in the speed and power is realized by the controlled concavity formation at the end of the motor nanowire using a sphere lithography protocol. Functionalization of the Au segments with lectin and antiprotein A antibody bioreceptors allows capture and transport of E. coli and S. aureus bacteria, respectively. Potential therapeutic applications are illustrated in connection to the addition of a pH-sensitive drug-loaded polymeric (PPy-PSS) segment. The attractive capabilities of these fuel-free acoustically driven functionalized Au-Ni-Au nanowires, along with the simple preparation procedure and minimal adverse effects of ultrasonic waves, make them highly attractive for diverse in vivo biomedical applications.

Identification of the Products from the Sulfonation of an Oleic Acid Methyl Ester

Sulfonation with SO3 of an oleic methyl ester has led to a mixture of sulfonates with potential properties as a surfactant, an emulsifier or even a wetting agent that can be used in detergent formulations. For the first time, the products from the sulfonation reaction with SO3 are identified.