Microrobots for Biomedicine: Unsolved Challenges and Opportunities for Translation.

Microrobots are being explored for biomedical applications, such as drug delivery, biological cargo transport, and minimally invasive surgery. However, current efforts largely focus on proof-of-concept studies with nontranslatable materials through a "design-and-apply" approach, limiting the potential for clinical adaptation. While these proof-of-concept studies have been key to advancing microrobot technologies, we believe that the distinguishing capabilities of microrobots will be most readily brought to patient bedsides through a "design-by-problem" approach, which involves focusing on unsolved problems to inform the design of microrobots with practical capabilities. As outlined below, we propose that the clinical translation of microrobots will be accelerated by a judicious choice of target applications, improved delivery considerations, and the rational selection of translation-ready biomaterials, ultimately reducing patient burden and enhancing the efficacy of therapeutic drugs for difficult-to-treat diseases.

Systemic Tumor Suppression via Macrophage-Driven Automated Homing of Metal-Phenolic-Gated Nanosponges for Metastatic Melanoma.

Cell-based therapies comprising the administration of living cells to patients for direct therapeutic activities have experienced remarkable success in the clinic, of which macrophages hold great potential for targeted drug delivery due to their inherent chemotactic mobility and homing ability to tumors with high efficiency. However, such targeted delivery of drugs through cellular systems remains a significant challenge due to the complexity of balancing high drug-loading with high accumulations in solid tumors. Herein, a tumor-targeting cellular drug delivery system (MAGN) by surface engineering of tumor-homing macrophages (Mφs) with biologically responsive nanosponges is reported. The pores of the nanosponges are blocked with iron-tannic acid complexes that serve as gatekeepers by holding encapsulated drugs until reaching the acidic tumor microenvironment. Molecular dynamics simulations and interfacial force studies are performed to provide mechanistic insights into the "ON-OFF" gating effect of the polyphenol-based supramolecular gatekeepers on the nanosponge channels. The cellular chemotaxis of the Mφ carriers enabled efficient tumor-targeted delivery of drugs and systemic suppression of tumor burden and lung metastases in vivo. The findings suggest that the MAGN platform offers a versatile strategy to efficiently load therapeutic drugs to treat advanced metastatic cancers with a high loading capacity of various therapeutic drugs.

Fallibility of tattooing colonic neoplasia ahead of laparoscopic resection: a retrospective cohort study.

INTRODUCTION: Precise geographical localisation of colonic neoplasia is a prerequisite for proper laparoscopic oncological resection. Preoperative endoscopic peri-tumoural tattoo practice is routinely recommended but seldom scrutinised. METHODS: A retrospective review of recent consecutive patients with preoperative endoscopic lesional tattoo who underwent laparoscopic colonic resection as identified from our prospectively maintained cancer database with supplementary clinical chart and radiological, histological, endoscopic and theatre database/logbook interrogation. RESULTS: Some 210 patients with 'tattooed' colonic neoplasia were identified, of whom 169 underwent laparoscopic surgery (mean age 68 years, median BMI 27.8kg/m2, male-to-female ratio 95:74). The majority of tumours were malignant (149; 88%), symptomatic (133; 79%) and proximal to the splenic flexure (92; 54%). Inaccurate colonoscopist localisation judgement occurred in 12% of cases, 60% of which were corrected by preoperative staging computed tomography scan. A useful lesional tattoo was absent in 11/169 cases (6.5%) being specifically stated as present in 104 operation notes (61%) and absent in 10 (5.9%). Tumours missing overt peritumoral tattoos intraoperatively were more likely to be smaller, earlier stage and injected longer preoperatively (p=0.006), although half had histological ink staining. Eight lesions missing tattoos were radiologically occult. Four (44%) of these patients had on-table colonoscopy, and five (55%) needed laparotomy (conversion rate 55% vs 23% overall, p<0.005) with one needing a second operation to resect the initially missed target lesion. Mean (range) operative duration and postoperative length of stay of those missing tattoos compared with those with tattoos was 200 (78-300) versus 188 (50-597) min and 15.5 (4-22) versus 12(4-70) days (p>0.05). CONCLUSIONS: Tattoo in advance of attempting laparoscopic resection is vital for precision cancer surgery especially for radiologically unseen tumours to avoid adverse clinical consequence.

Magnetic systems for cancer immunotherapy.

Immunotherapy is a rapidly developing area of cancer treatment due to its higher specificity and potential for greater efficacy than traditional therapies. Immune cell modulation through the administration of drugs, proteins, and cells can enhance antitumoral responses through pathways that may be otherwise inhibited in the presence of immunosuppressive tumors. Magnetic systems offer several advantages for improving the performance of immunotherapies, including increased spatiotemporal control over transport, release, and dosing of immunomodulatory drugs within the body, resulting in reduced off-target effects and improved efficacy. Compared to alternative methods for stimulating drug release such as light and pH, magnetic systems enable several distinct methods for programming immune responses. First, we discuss how magnetic hyperthermia can stimulate immune cells and trigger thermoresponsive drug release. Second, we summarize how magnetically targeted delivery of drug carriers can increase the accumulation of drugs in target sites. Third, we review how biomaterials can undergo magnetically driven structural changes to enable remote release of encapsulated drugs. Fourth, we describe the use of magnetic particles for targeted interactions with cellular receptors for promoting antitumor activity. Finally, we discuss translational considerations of these systems, such as toxicity, clinical compatibility, and future opportunities for improving cancer treatment.

Rapid capture of biomolecules from blood via stimuli-responsive elastomeric particles for acoustofluidic separation.

The detection of biomarkers in blood often requires extensive and time-consuming sample preparation to remove blood cells and concentrate the biomarker(s) of interest. We demonstrate proof-of-concept for a chip-based, acoustofluidic method that enables the rapid capture and isolation of a model protein biomarker (i.e., streptavidin) from blood for off-chip quantification. Our approach makes use of two key components - namely, soluble, thermally responsive polypeptides fused to ligands for the homogeneous capture of biomarkers from whole blood and silicone microparticles functionalized with similar, tethered, thermally responsive polypeptides. When the two components are mixed together and subjected to a mild thermal trigger, the thermally responsive moieties undergo a phase transition, causing the untethered (soluble) polypeptides to co-aggregate with the particle-bound polypeptides. The mixture is then diluted with warm buffer and injected into a microfluidic channel supporting a bulk acoustic standing wave. The biomarker-bearing particles migrate to the pressure antinodes, whereas blood cells migrate to the pressure node, leading to rapid separation with efficiencies exceeding 90% in a single pass. The biomarker-bearing particles can then be analyzed via flow cytometry, with a limit of detection of 0.75 nM for streptavidin spiked in blood plasma. Finally, by cooling the solution below the solubility temperature of the polypeptides, greater than 75% of the streptavidin is released from the microparticles, offering a unique approach for downstream analysis (e.g., sequencing or structural analysis). Overall, this methodology has promise for the detection, enrichment and analysis of some biomarkers from blood and other complex biological samples.

Engineering of Living Cells with Polyphenol-Functionalized Biologically Active Nanocomplexes.

Approaches to safely and effectively augment cellular functions without compromising the inherent biological properties of the cells, especially through the integration of biologically labile domains, remain of great interest. Here, a versatile strategy to assemble biologically active nanocomplexes, including proteins, DNA, mRNA, and even viral carriers, on cellular surfaces to generate a cell-based hybrid system referred to as "Cellnex" is established. This strategy can be used to engineer a wide range of cell types used in adoptive cell transfers, including erythrocytes, macrophages, NK cells, T cells, etc. Erythrocytenex can enhance the delivery of cargo proteins to the lungs in vivo by 11-fold as compared to the free cargo counterpart. Biomimetic microfluidic experiments and modeling provided detailed insights into the targeting mechanism. In addition, Macrophagenex is capable of enhancing the therapeutic efficiency of anti-PD-L1 checkpoint inhibitors in vivo. This simple and adaptable approach may offer a platform for the rapid generation of complex cellular systems.

Cellular backpacks for macrophage immunotherapy.

Adoptive cell transfers have emerged as a disruptive approach to treat disease in a manner that is more specific than using small-molecule drugs; however, unlike traditional drugs, cells are living entities that can alter their function in response to environmental cues. In the present study, we report an engineered particle referred to as a "backpack" that can robustly adhere to macrophage surfaces and regulate cellular phenotypes in vivo. Backpacks evade phagocytosis for several days and release cytokines to continuously guide the polarization of macrophages toward antitumor phenotypes. We demonstrate that these antitumor phenotypes are durable, even in the strongly immunosuppressive environment of a murine breast cancer model. Conserved phenotypes led to reduced metastatic burdens and slowed tumor growths compared with those of mice treated with an equal dose of macrophages with free cytokine. Overall, these studies highlight a new pathway to control and maintain phenotypes of adoptive cellular immunotherapies.

Intra-Arterial Chemotherapy for Retinoblastoma in Infants ≤10 kg: 74 Treated Eyes with 222 IAC Sessions.

BACKGROUND AND PURPOSE: Intra-arterial chemotherapy for retinoblastoma has dramatically altered the natural history of the disease. The remarkable outcomes associated with a high safety profile have pushed the envelope to offer treatment for patients weighing ≤10 kg. The purpose was to determine the efficacy and safety of IAC infusions performed in infants weighing ≤10 kg with intraocular retinoblastoma. MATERIALS AND METHODS: A retrospective chart review was performed for patients diagnosed with retinoblastoma and managed with intra-arterial chemotherapy. RESULTS: The total study cohort included 207 retinoblastoma tumors of 207 eyes in 196 consecutive patients who underwent 658 intra-arterial chemotherapy infusions overall. Of these, patient weights were ≤10 kg in 69 (35.2%) and >10 kg in 127 (64.8%) patients. Comparison (≤10 kg versus >10 kg) revealed that the total number of intra-arterial chemotherapy infusions was 222 versus 436. Periprocedural complications were not significantly different (2 [0.9%] versus 2 [0.5%]; P = .49). Cumulative radiation exposure per eye was significantly lower in infants weighing ≤10 kg (5.0 Gym2 versus 7.7 Gym2; P = .01). Patients weighing ≤10 kg had a greater frequency of complete tumor regression (82.6% versus 60.9%; P = .02). Mean fluoroscopy time was not significantly different (7.5 versus 7.2; P = .71). There was a significant difference in the frequency of enucleation (16 [21.6%] versus 52 [39.1%]; P = .01). Patients weighing ≤10 kg had greater number of aborted procedures (12 [5.4%] versus 7 [1.6%]; P = .01). On multivariate analysis, weight ≤10 kg was not an independent predictor of complications or procedure failure. CONCLUSIONS: Intra-arterial chemotherapy in patients weighing ≤10 kg is a safe and effective treatment.

Design principles of drug combinations for chemotherapy.

Combination chemotherapy is the leading clinical option for cancer treatment. The current approach to designing drug combinations includes in vitro optimization to maximize drug cytotoxicity and/or synergistic drug interactions. However, in vivo translatability of drug combinations is complicated by the disparities in drug pharmacokinetics and activity. In vitro cellular assays also fail to represent the immune response that can be amplified by chemotherapy when dosed appropriately. Using three common chemotherapeutic drugs, gemcitabine (GEM), irinotecan (IRIN), and a prodrug form of 5-flurouracil (5FURW), paired with another common drug and immunogenic cell death inducing agent, doxorubicin (DOX), we sought to determine the in vitro parameters that predict the in vivo outcomes of drug combinations in the highly aggressive orthotopic 4T1 murine breast cancer model. With liposomal encapsulation of each drug pair, we enabled uniform drug pharmacokinetics across the drug combinations, thus allowing us to study the inherent benefits of the drug pairs and compare them to DOX liposomes representative of DOXIL®. Surprisingly, the Hill coefficient (HC) of the in vitro dose-response Hill equation provided a better prediction of in vivo efficacy than drug IC50 or combination index. GEM/DOX liposomes exhibited a high HC in vitro and an increase in M1/M2 macrophage ratio in vivo. Hence, GEM/DOX liposomes were further investigated in a long-term survival study and compared against doxorubicin liposomes and gemcitabine liposomes. The GEM/DOX liposome-treated group had the longest median survival time, double that of the DOX liposome-treated group and 3.4-fold greater than that of the untreated controls. Our studies outline the development of a more efficacious formulation than clinically representative liposomal doxorubicin for breast cancer treatment and presents a novel strategy for designing cancer drug combinations.

Migration of Microparticle-Containing Amoeba through Constricted Environments.

In many situations, cells migrate through tiny orifices. Examples include the extravasation of immune cells from the bloodstream for fighting infections, the infiltration of cancer cells during metastasis, and the migration of human pathogens. An extremely motile and medically relevant type of human pathogen is Acanthamoeba castellanii. In the study presented here, we investigated how a combination of microparticles and microstructured interfaces controls the migration of A. castellanii trophozoites. The microinterfaces comprised well-defined micropillar arrays, and the trophozoites easily migrated through the given constrictions by adapting the shape and size of their intracellular vacuoles and by adapting intracellular motion. After feeding the trophozoite cells in microinterfaces with synthetic, stiff microparticles of various sizes and shapes, their behavior changed drastically: if the particles were smaller than the micropillar gap, migration was still possible. If the cells incorporated particles larger than the pillar gap, they could become immobilized but could also display remarkable problem-solving capabilities. For example, they turned rod-shaped microparticles such that their short axis fit through the pillar gap or they transported the particles above the structure. As migration is a crucial contribution to A. castellanii pathogenicity and is also relevant to other biological processes in microenvironments, such as cancer metastasis, our results provide an interesting strategy for controlling the migration of cells containing intracellular particles by microstructured interfaces that serve as migration-limiting environments.

Materials for Immunotherapy.

Breakthroughs in materials engineering have accelerated the progress of immunotherapy in preclinical studies. The interplay of chemistry and materials has resulted in improved loading, targeting, and release of immunomodulatory agents. An overview of the materials that are used to enable or improve the success of immunotherapies in preclinical studies is presented, from immunosuppressive to proinflammatory strategies, with particular emphasis on technologies poised for clinical translation. The materials are organized based on their characteristic length scale, whereby the enabling feature of each technology is organized by the structure of that material. For example, the mechanisms by which i) nanoscale materials can improve targeting and infiltration of immunomodulatory payloads into tissues and cells, ii) microscale materials can facilitate cell-mediated transport and serve as artificial antigen-presenting cells, and iii) macroscale materials can form the basis of artificial microenvironments to promote cell infiltration and reprogramming are discussed. As a step toward establishing a set of design rules for future immunotherapies, materials that intrinsically activate or suppress the immune system are reviewed. Finally, a brief outlook on the trajectory of these systems and how they may be improved to address unsolved challenges in cancer, infectious diseases, and autoimmunity is presented.

Drug delivery to macrophages: A review of targeting drugs and drug carriers to macrophages for inflammatory diseases.

Macrophages play a key role in defending against foreign pathogens, healing wounds, and regulating tissue homeostasis. Driving this versatility is their phenotypic plasticity, which enables macrophages to respond to subtle cues in tightly coordinated ways. However, when this coordination is disrupted, macrophages can aid the progression of numerous diseases, including cancer, cardiovascular disease, and autoimmune disease. The central link between these disorders is aberrant macrophage polarization, which misguides their functional programs, secretory products, and regulation of the surrounding tissue microenvironment. As a result of their important and deterministic roles in both health and disease, macrophages have gained considerable attention as targets for drug delivery. Here, we discuss the role of macrophages in the initiation and progression of various inflammatory diseases, summarize the leading drugs used to regulate macrophages, and review drug delivery systems designed to target macrophages. We emphasize strategies that are approved for clinical use or are poised for clinical investigation. Finally, we provide a prospectus of the future of macrophage-targeted drug delivery systems.

Role of synergy and immunostimulation in design of chemotherapy combinations: An analysis of doxorubicin and camptothecin.

Combination chemotherapy is often employed to improve therapeutic efficacies of drugs. However, traditional combination regimens often utilize drugs at or near-their maximum tolerated doses (MTDs), elevating the risk of dose-related toxicity and impeding their clinical success. Further, high doses of adjuvant or neoadjuvant chemotherapies can cause myeloablation, which compromises the immune response and hinders the efficacy of chemotherapy as well as accompanying treatments such as immunotherapy. Clinical outcomes can be improved if chemotherapy combinations are designed to reduce the overall doses without compromising their therapeutic efficacy. To this end, we investigated a combination of camptothecin (CPT) with doxorubicin (DOX) as a low-dose treatment option for breast cancer. DOX-CPT combinations were synergistic in several breast cancer cell lines in vitro and one particular ratio displayed extremely high synergy on human triple negative breast cancer cells (MDA-MB-231). This combination led to excellent long-term survival of mice bearing MDA-MB-231 tumors at doses roughly five-fold lower than the reported MTD values of its constituent drugs. Impact of low dose DOX-CPT treatment on local tumor immune environment was assessed in immunocompetent mice bearing breast cancer (4T1) tumors. The combination was not only superior in inhibiting the disease progression compared to individual drugs, but it also generated a more favorable antitumor immunogenic response. Engineering DOX and CPT ratios to manifest synergy enables treatment at doses much lower than their MTDs, which could ultimately facilitate their translation into the clinic as a promising combination for breast cancer treatment.

Retinal sensitivity and photoreceptor arrangement changes secondary to congenital simple hamartoma of retinal pigment epithelium.

BACKGROUND: The congenital simple hamartoma of the retinal pigment epithelium is a benign lesion and previous observations with noninvasive imaging have detected potential photoreceptor abnormalities and retinal function interplay. CASE PRESENTATION: A 35-year-old woman was found to have an asymptomatic, solitary, circumscribed, pigmented lesion in her left eye. The patient underwent ophthalmic examination including multimodal evaluation with fluorescein angiography, near-infrared reflectance scanning laser ophthalmoscopy, blue autofluorescence, enhanced-depth imaging spectralis B-scan optical coherence tomography (EDI-SBOCT), en face OCT angiography (OCT-A) and microperimetry plus adaptive optics imaging. Ophthalmoscopic examination revealed a juxtafoveolar pigmented lesion with feeding retinal arteriole, consistent with congenital simple hamartoma of RPE. There was no macular edema, exudation, hemorrhage, traction or subretinal fluid. Multimodal imaging of the mass using fluorescein angiography revealed intra-lesion late staining, near-infrared reflectance imaging demonstrated intrinsic hyperreflectivity, short-wavelength autofluorescence and red-free filter photography revealed blocked signal, and SBOCT showed abrupt shadowing. On OCT-A, an exclusive ring-shaped vascular circuit with increased foveal avascular zone was noted. Adaptive optics revealed cell density arrangement and retinal sensitivity correlations on microperimetry. CONCLUSION: These findings suggest that this hamartomatous lesion might cause specific cellular changes that impact retinal sensitivity response and potentially result from vasculature malnourishment to the outer retinal layers.

Comparison of Germline versus Somatic BAP1 Mutations for Risk of Metastasis in Uveal Melanoma.

BACKGROUND: Germline mutations in BAP1 have been associated with BAP1-Tumor Predisposition Syndrome (BAP1-TPDS), a predisposition to multiple tumors within a family that includes uveal melanoma (UM), cutaneous melanoma, malignant mesothelioma and renal cell carcinoma. Alternatively, somatic mutations in BAP1 in UM have been associated with high risk for metastasis. In this study, we compare the risk of metastasis in UM that carry germline versus somatic BAP1 mutations and mutation-negative tumors. METHODS: DNA extracted from 142 UM and matched blood samples was sequenced using Sanger or next generation sequencing to identify BAP1 gene mutations. RESULTS: Eleven of 142 UM (8%) carried germline BAP1 mutations, 43 (30%) had somatic mutations, and 88 (62%) were mutation-negative. All BAP1 mutations identified in blood samples were also present in the matched UM. There were 52 unique mutations in 54 tumors. All were pathogenic or likely pathogenic. A comparison of tumors carrying somatic vs. germline mutations, or no mutations, showed a higher frequency of metastasis in tumors carrying somatic mutations: 74% vs. 36%, P=0.03 and 74% vs. 26% P<0.001, respectively. Tumors with a somatic mutation compared to mutation-negative had an older age of diagnosis of (61.8 vs. 52.2 years, P=0.002), and shorter time to metastasis (16 vs. 26 months, P=0.04). Kaplan-Meier analysis further showed that tumors with somatic (vs. germline) mutations demonstrated a greater metastatic risk (P=0.03). Cox multivariate analysis showed in addition to chromosome-3 monosomy and larger tumor diameter, the presence of BAP1 somatic, but not germline mutations, was significantly associated with risk of metastasis(P=0.02). Personal or family history of BAP1-TPDS was available for 79 of the cases. All eight cases with germline mutations reported a history of BAP1-TPDS, which was significantly greater than what was observed in cases with somatic mutations (10 of 23, P=0.009) or mutation-negative cases (11 of 48, P<0.001). CONCLUSIONS: Defining germline vs. somatic nature of BAP1 mutations in UM can inform the individual about both the risk of metastasis, and the time to metastasis, which are critically important outcomes for the individual. This information can also change the cascade screening and surveillance of family members.

Peritoneal metastases from extra-abdominal cancer - A population-based study.

INTRODUCTION: Peritoneal metastases (PM) are predominantly seen as a manifestation of intra-abdominal malignancy such as colorectal or ovarian cancer. However, extra-abdominal primary cancer can also metastasise to the peritoneum. Population-based data on the incidence of PM from extra-abdominal cancer is lacking. This study aims to assess the patterns and survival of patients in Ireland with PM from extra-abdominal cancers. METHODS: The National Cancer Registry of Ireland database was interrogated to identify patients diagnosed with PM from extra-abdominal malignancy during the period 1994-2012. Patient demographics and tumour characteristics were analysed. RESULTS: 5791 patients were diagnosed with PM during the study period. Of these, 543 (9%) had an extra-abdominal primary malignancy. Breast (40.8%), lung (25.6%) and melanoma (9.3%) were the most common extra-abdominal cancers to develop PM. The majority of patients with peritoneal metastases of breast origin (75%) were diagnosed at a long interval (median interval 59.5 months; range = 1-485) from the diagnosis of the primary. The median survival from diagnosis of PM was 5.8 months compared with 22.6 months from diagnosis of stage IV disease without peritoneal involvement. Survival in patients with lung cancer and melanoma who developed PM was very poor and similar to that in patients with stage IV disease not involving the peritoneum. CONCLUSION: This is the first population-based study to report the incidence of PM secondary to extra-abdominal malignancy. The most common primary cancers were melanoma, breast and lung cancer. Metastatic disease to the peritoneum was uniformly associated with a poor prognosis.