Reset of hippocampal-prefrontal circuitry facilitates learning.

The ability to rapidly adapt to novel situations is essential for survival, and this flexibility is impaired in many neuropsychiatric disorders1. Thus, understanding whether and how novelty prepares, or primes, brain circuitry to facilitate cognitive flexibility has important translational relevance. Exposure to novelty recruits the hippocampus and medial prefrontal cortex (mPFC)2 and may prime hippocampal-prefrontal circuitry for subsequent learning-associated plasticity. Here we show that novelty resets the neural circuits that link the ventral hippocampus (vHPC) and the mPFC, facilitating the ability to overcome an established strategy. Exposing mice to novelty disrupted a previously encoded strategy by reorganizing vHPC activity to local theta (4-12 Hz) oscillations and weakening existing vHPC-mPFC connectivity. As mice subsequently adapted to a new task, vHPC neurons developed new task-associated activity, vHPC-mPFC connectivity was strengthened, and mPFC neurons updated to encode the new rules. Without novelty, however, mice adhered to their established strategy. Blocking dopamine D1 receptors (D1Rs) or inhibiting novelty-tagged cells that express D1Rs in the vHPC prevented these behavioural and physiological effects of novelty. Furthermore, activation of D1Rs mimicked the effects of novelty. These results suggest that novelty promotes adaptive learning by D1R-mediated resetting of vHPC-mPFC circuitry, thereby enabling subsequent learning-associated circuit plasticity.

Adult-born neurons maintain hippocampal cholinergic inputs and support working memory during aging.

Adult neurogenesis is reduced during aging and impaired in disorders of stress, memory, and cognition though its normal function remains unclear. Moreover, a systems level understanding of how a small number of young hippocampal neurons could dramatically influence brain function is lacking. We examined whether adult neurogenesis sustains hippocampal connections cumulatively across the life span. Long-term suppression of neurogenesis as occurs during stress and aging resulted in an accelerated decline in hippocampal acetylcholine signaling and a slow and progressing emergence of profound working memory deficits. These deficits were accompanied by compensatory reorganization of cholinergic dentate gyrus inputs with increased cholinergic innervation to the ventral hippocampus and recruitment of ventrally projecting neurons by the dorsal projection. While increased cholinergic innervation was dysfunctional and corresponded to overall decreases in cholinergic levels and signaling, it could be recruited to correct the resulting memory dysfunction even in old animals. Our study demonstrates that hippocampal neurogenesis supports memory by maintaining the septohippocampal cholinergic circuit across the lifespan.  It also provides a systems level explanation for the progressive nature of memory deterioration during normal and pathological aging and indicates that the brain connectome is malleable by experience.

The Utility of AI in Writing a Scientific Review Article on the Impacts of COVID-19 on Musculoskeletal Health.

PURPOSE OF REVIEW: There were two primary purposes to our reviews. First, to provide an update to the scientific community about the impacts of COVID-19 on musculoskeletal health. Second, was to determine the value of using a large language model, ChatGPT 4.0, in the process of writing a scientific review article. To accomplish these objectives, we originally set out to write three review articles on the topic using different methods to produce the initial drafts of the review articles. The first review article was written in the traditional manner by humans, the second was to be written exclusively using ChatGPT (AI-only or AIO), and the third approach was to input the outline and references selected by humans from approach 1 into ChatGPT, using the AI to assist in completing the writing (AI-assisted or AIA). All review articles were extensively fact-checked and edited by all co-authors leading to the final drafts of the manuscripts, which were significantly different from the initial drafts. RECENT FINDINGS: Unfortunately, during this process, it became clear that approach 2 was not feasible for a very recent topic like COVID-19 as at the time, ChatGPT 4.0 had a cutoff date of September 2021 and all articles published after this date had to be provided to ChatGPT, making approaches 2 and 3 virtually identical. Therefore, only two approaches and two review articles were written (human and AI-assisted). Here we found that the human-only approach took less time to complete than the AI-assisted approach. This was largely due to the number of hours required to fact-check and edit the AI-assisted manuscript. Of note, the AI-assisted approach resulted in inaccurate attributions of references (about 20%) and had a higher similarity index suggesting an increased risk of plagiarism. The main aim of this project was to determine whether the use of AI could improve the process of writing a scientific review article. Based on our experience, with the current state of technology, it would not be advised to solely use AI to write a scientific review article, especially on a recent topic.

COVID-19 and Bone Loss: A Review of Risk Factors, Mechanisms, and Future Directions.

PURPOSE OF REVIEW: SARS-CoV-2 drove the catastrophic global phenomenon of the COVID-19 pandemic resulting in a multitude of systemic health issues, including bone loss. The purpose of this review is to summarize recent findings related to bone loss and potential mechanisms. RECENT FINDINGS: The early clinical evidence indicates an increase in vertebral fractures, hypocalcemia, vitamin D deficiencies, and a loss in BMD among COVID-19 patients. Additionally, lower BMD is associated with more severe SARS-CoV-2 infection. Preclinical models have shown bone loss and increased osteoclastogenesis. The bone loss associated with SARS-CoV-2 infection could be the result of many factors that directly affect the bone such as higher inflammation, activation of the NLRP3 inflammasome, recruitment of Th17 cells, the hypoxic environment, and changes in RANKL/OPG signaling. Additionally, SARS-CoV-2 infection can exert indirect effects on the skeleton, as mechanical unloading may occur with severe disease (e.g., bed rest) or with BMI loss and muscle wasting that has also been shown to occur with SARS-CoV-2 infection. Muscle wasting can also cause systemic issues that may influence the bone. Medications used to treat SARS-CoV-2 infection also have a negative effect on the bone. Lastly, SARS-CoV-2 infection may also worsen conditions such as diabetes and negatively affect kidney function, all of which could contribute to bone loss and increased fracture risk. SARS-CoV-2 can negatively affect the bone through multiple direct and indirect mechanisms. Future work will be needed to determine what patient populations are at risk of COVID-19-related increases in fracture risk, the mechanisms behind bone loss, and therapeutic options. This review article is part of a series of multiple manuscripts designed to determine the utility of using artificial intelligence for writing scientific reviews.

SARS-CoV-2 and its Multifaceted Impact on Bone Health: Mechanisms and Clinical Evidence.

PURPOSE OF REVIEW: SARS-CoV-2 infection, the culprit of the COVID-19 pandemic, has been associated with significant long-term effects on various organ systems, including bone health. This review explores the current understanding of the impacts of SARS-CoV-2 infection on bone health and its potential long-term consequences. RECENT FINDINGS: As part of the post-acute sequelae of SARS-CoV-2 infection, bone health changes are affected by COVID-19 both directly and indirectly, with multiple potential mechanisms and risk factors involved. In vitro and preclinical studies suggest that SARS-CoV-2 may directly infect bone marrow cells, leading to alterations in bone structure and osteoclast numbers. The virus can also trigger a robust inflammatory response, often referred to as a "cytokine storm", which can stimulate osteoclast activity and contribute to bone loss. Clinical evidence suggests that SARS-CoV-2 may lead to hypocalcemia, altered bone turnover markers, and a high prevalence of vertebral fractures. Furthermore, disease severity has been correlated with a decrease in bone mineral density. Indirect effects of SARS-CoV-2 on bone health, mediated through muscle weakness, mechanical unloading, nutritional deficiencies, and corticosteroid use, also contribute to the long-term consequences. The interplay of concurrent conditions such as diabetes, obesity, and kidney dysfunction with SARS-CoV-2 infection further complicates the disease's impact on bone health. SARS-CoV-2 infection directly and indirectly affects bone health, leading to potential long-term consequences. This review article is part of a series of multiple manuscripts designed to determine the utility of using artificial intelligence for writing scientific reviews.

Multi-omics approach identifies germline regulatory variants associated with hematopoietic malignancies in retriever dog breeds.

Histiocytic sarcoma is an aggressive hematopoietic malignancy of mature tissue histiocytes with a poorly understood etiology in humans. A histologically and clinically similar counterpart affects flat-coated retrievers (FCRs) at unusually high frequency, with 20% developing the lethal disease. The similar clinical presentation combined with the closed population structure of dogs, leading to high genetic homogeneity, makes dogs an excellent model for genetic studies of cancer susceptibility. To determine the genetic risk factors underlying histiocytic sarcoma in FCRs, we conducted multiple genome-wide association studies (GWASs), identifying two loci that confer significant risk on canine chromosomes (CFA) 5 (Pwald = 4.83x10-9) and 19 (Pwald = 2.25x10-7). We subsequently undertook a multi-omics approach that has been largely unexplored in the canine model to interrogate these regions, generating whole genome, transcriptome, and chromatin immunoprecipitation sequencing. These data highlight the PI3K pathway gene PIK3R6 on CFA5, and proximal candidate regulatory variants that are strongly associated with histiocytic sarcoma and predicted to impact transcription factor binding. The CFA5 association colocalizes with susceptibility loci for two hematopoietic malignancies, hemangiosarcoma and B-cell lymphoma, in the closely related golden retriever breed, revealing the risk contribution this single locus makes to multiple hematological cancers. By comparison, the CFA19 locus is unique to the FCR and harbors risk alleles associated with upregulation of TNFAIP6, which itself affects cell migration and metastasis. Together, these loci explain ~35% of disease risk, an exceptionally high value that demonstrates the advantages of domestic dogs for complex trait mapping and genetic studies of cancer susceptibility.

Long-range neural synchrony in behavior.

Long-range synchrony between distant brain regions accompanies multiple forms of behavior. This review compares and contrasts the methods by which long-range synchrony is evaluated in both humans and model animals. Three examples of behaviorally relevant long-range synchrony are discussed in detail: gamma-frequency synchrony during visual perception, hippocampal-prefrontal synchrony during working memory, and prefrontal-amygdala synchrony during anxiety. Implications for circuit mechanism, translation, and clinical relevance are discussed.

In vivo dynamics of senescence in rhabdomyolysis-induced acute kidney injury.

Cellular senescence is involved in the pathogenesis of various diseases, including acute kidney injury (AKI). AKI is defined as a sudden loss of kidney function. In severe AKI, irreversible loss of kidney cells can occur. Cellular senescence might contribute to this maladaptive tubular repair, though, its pathophysiological role in vivo is incompletely understood. In this study, we used p16-CreERT2-tdTomato mice in which cells with high p16 expression, a prototypical senescent marker, are labeled with tdTomato fluorescence. Then, we induced AKI by rhabdomyolysis and traced the cells with high p16 expression following AKI. We proved that the induction of senescence was observed predominantly in proximal tubular epithelial cells (PTECs) and occurred in a relatively acute phase within 1-3 days after AKI. These acute senescent PTECs were spontaneously eliminated by day 15. On the contrary, the generation of senescence in PTECs persisted during the chronic recovery phase. We also confirmed that the kidney function did not fully recover on day 15. These results suggest that the chronic generation of senescent PTECs might contribute to maladaptive recovery from AKI and lead to chronic kidney disease progression.

Decreased Anogenital Gonorrhea and Chlamydia in Transgender and Gender Diverse Primary Care Patients Receiving Gender-Affirming Hormone Therapy.

BACKGROUND: Transgender and gender diverse (TGD) adults in the U.S. experience health disparities, including in anogenital sexually transmitted infections (STI). Gender-affirming hormone therapy (GAHT) is known to be medically necessary and improve health. Few studies have assessed the effect of GAHT on STI diagnoses. OBJECTIVE: To evaluate the effect of GAHT delivered in primary care as an intervention to improve STI outcomes for TGD adults. DESIGN: LEGACY is a longitudinal, multisite cohort study of adult TGD primary care patients from two federally qualified community health centers in Boston, MA, and New York, NY. PARTICIPANTS: Electronic health record data for eligible adult TGD patients contributed to the LEGACY research data warehouse (RDW). A total of 6330 LEGACY RDW patients were followed from 2016 to 2019, with 2555 patients providing STI testing data. MAIN MEASURES: GAHT exposure was being prescribed hormones, and the clinical outcome was anogenital gonorrhea or chlamydia diagnoses. Log-Poisson generalized estimating equations assessed the effect of prescription GAHT on primary outcomes, adjusting for age, race, ethnicity, gender identity, poverty level, health insurance, clinical site, and cohort years. KEY RESULTS: The median age was 28 years (IQR = 13); the racial breakdown was 20.4% Black, 8.1% Multiracial, 6.9% Asian/Pacific Islander, 1.8% Other; 62.8% White; 21.3% Hispanic/Latinx; 47.0% were assigned female at birth, and 16.0% identified as nonbinary. 86.3% were prescribed hormones. Among those tested, the percentage of patients with a positive anogenital STI diagnosis ranged annually from 10.0 to 12.5% between 2016 and 2019. GAHT prescription was associated with a significant reduction in the risk of anogenital STI diagnosis (aRR = 0.75; 95% CI = 0.59-0.96) over follow-up. CONCLUSIONS: GAHT delivered in primary care was associated with less STI morbidity in this TGD cohort over follow-up. Patients may benefit from individualized and tailored clinical care alongside GAHT to optimize STI outcomes.

Developmental impact of glutamate transporter overexpression on dopaminergic neuron activity and stereotypic behavior.

Obsessive-compulsive disorder (OCD) is a disabling condition that often begins in childhood. Genetic studies in OCD have pointed to SLC1A1, which encodes the neuronal glutamate transporter EAAT3, with evidence suggesting that increased expression contributes to risk. In mice, midbrain Slc1a1 expression supports repetitive behavior in response to dopaminergic agonists, aligning with neuroimaging and pharmacologic challenge studies that have implicated the dopaminergic system in OCD. These findings suggest that Slc1a1 may contribute to compulsive behavior through altered dopaminergic transmission; however, this theory has not been mechanistically tested. To examine the developmental impact of Slc1a1 overexpression on compulsive-like behaviors, we, therefore, generated a novel mouse model to perform targeted, reversible overexpression of Slc1a1 in dopaminergic neurons. Mice with life-long overexpression of Slc1a1 showed a significant increase in amphetamine (AMPH)-induced stereotypy and hyperlocomotion. Single-unit recordings demonstrated that Slc1a1 overexpression was associated with increased firing of dopaminergic neurons. Furthermore, dLight1.1 fiber photometry showed that these behavioral abnormalities were associated with increased dorsal striatum dopamine release. In contrast, no impact of overexpression was observed on anxiety-like behaviors or SKF-38393-induced grooming. Importantly, overexpression solely in adulthood failed to recapitulate these behavioral phenotypes, suggesting that overexpression during development is necessary to generate AMPH-induced phenotypes. However, doxycycline-induced reversal of Slc1a1/EAAT3 overexpression in adulthood normalized both the increased dopaminergic firing and AMPH-induced responses. These data indicate that the pathologic effects of Slc1a1/EAAT3 overexpression on dopaminergic neurotransmission and AMPH-induced stereotyped behavior are developmentally mediated, and support normalization of EAAT3 activity as a potential treatment target for basal ganglia-mediated repetitive behaviors.

Development of a Reliable Surgical Quality Assurance System for 2-stage Esophagectomy in Randomized Controlled Trials.

OBJECTIVE: The aim was to develop a reliable surgical quality assurance system for 2-stage esophagectomy. This development was conducted during the pilot phase of the multicenter ROMIO trial, collaborating with international experts. SUMMARY OF BACKGROUND DATA: There is evidence that the quality of surgical performance in randomized controlled trials influences clinical outcomes, quality of lymphadenectomy and loco-regional recurrence. METHODS: Standardization of 2-stage esophagectomy was based on structured observations, semi-structured interviews, hierarchical task analysis, and a Delphi consensus process. This standardization provided the structure for the operation manual and video and photographic assessment tools. Reliability was examined using generalizability theory. RESULTS: Hierarchical task analysis for 2-stage esophagectomy comprised fifty-four steps. Consensus (75%) agreement was reached on thirty-nine steps, whereas fifteen steps had a majority decision. An operation manual and record were created. A thirty five-item video assessment tool was developed that assessed the process (safety and efficiency) and quality of the end product (anatomy exposed and lymphadenectomy performed) of the operation. The quality of the end product section was used as a twenty seven-item photographic assessment tool. Thirty-one videos and fifty-three photographic series were submitted from the ROMIO pilot phase for assessment. The overall G-coefficient for the video assessment tool was 0.744, and for the photographic assessment tool was 0.700. CONCLUSIONS: A reliable surgical quality assurance system for 2-stage esophagectomy has been developed for surgical oncology randomized controlled trials. ETHICAL APPROVAL: 11/NW/0895 and confirmed locally as appropriate, 12/SW/0161, 16/SW/0098.Trial registration number: ISRCTN59036820, ISRCTN10386621.

Ethical and regulatory issues of stem cell-derived 3-dimensional organoid and tissue therapy for personalised regenerative medicine.

BACKGROUND: Regenerative medicine has the potential to treat genetic disorders and replace damaged or missing tissue. The use of donor or animal tissue raises many well-known issues, including limited tissue availability, the possibility of rejection and patient infection. Stem cell therapy raised hope of overcoming these issues, but created new risks including tumour formation and limited benefit if the desired target tissue does not form. The recent development of 3-dimensional tissues, including organoids, allows the creation of more complex tissues for personalised regenerative medicine. METHODS: This article details the potential health risks of 3-dimensional organoid and tissue therapy versus dissociated stem cell therapy. The current ethical and regulatory issues surrounding 3-dimensional organoid and tissue therapy are presented with a focus on the highly influential FDA and International Society of Stem Cell Research (ISSCR) guidelines. CONCLUSIONS: The potential use of 3-dimensional organoid and tissue therapy may deliver greater patient benefits than other regenerative medicine approaches, but raises new health and ethical risks. Preclinical testing of these therapies will not mitigate some of their risks; they may only be understood after first-in-human trials. The potential irreversibility and high risk of these therapies affects how clinical trials should be structured, including post-trial care for participants.

CDKL5 deficiency disorder: molecular insights and mechanisms of pathogenicity to fast-track therapeutic development.

CDKL5 deficiency disorder (CDD) is an X-linked brain disorder of young children and is caused by pathogenic variants in the cyclin-dependent kinase-like 5 (CDKL5) gene. Individuals with CDD suffer infantile onset, drug-resistant seizures, severe neurodevelopmental impairment and profound lifelong disability. The CDKL5 protein is a kinase that regulates key phosphorylation events vital to the development of the complex neuronal network of the brain. Pathogenic variants identified in patients may either result in loss of CDKL5 catalytic activity or are hypomorphic leading to partial loss of function. Whilst the progressive nature of CDD provides an excellent opportunity for disease intervention, we cannot develop effective therapeutics without in-depth knowledge of CDKL5 function in human neurons. In this mini review, we summarize new findings on the function of CDKL5. These include CDKL5 phosphorylation targets and the consequence of disruptions on signaling pathways in the human brain. This new knowledge of CDKL5 biology may be leveraged to advance targeted drug discovery and rapid development of treatments for CDD. Continued development of effective humanized models will further propel our understanding of CDD biology and may permit the development and testing of therapies that will significantly alter CDD disease trajectory in young children.

Restoring vision using optogenetics without being blind to the risks.

Retinit is pigmentosa is an incurable degenerative disease that causes loss of light-sensitive cells in the retina and leads to severe vision impairment. The development of optogenetics has created great hype around its potential to treat retinitis pigmentosa by the introduction of light-sensitive proteins into other neural cells in the retina. The first-in-human studies of optogenetic treatment for this disease have recently been reported (NCT02556736 and NCT03326336). The treatment involves irreversible gene therapy and requires access to specially designed goggles to deliver light to the treated eye. These highly innovative and high-profile clinical trials raise numerous ethical issues that must be addressed during the early phases of research and clinical testing to ensure trial participants are treated fairly and can provide appropriate informed consent.

"Focus more on what's right instead of what's wrong:" research priorities identified by a sample of transgender and gender diverse community health center patients.

BACKGROUND: Transgender and gender diverse (TGD) individuals disproportionately experience disparate health outcomes compared to their cisgender peers. This study aimed to collect qualitative data from a sample of TGD community health center patients on health research priorities to inform future TGD-centered research in the field of TGD health. METHODS: Between September-November of 2018, four focus groups (two groups in Boston MA, two in New York NY; n = 28 individuals) were held to evaluate community-identified TGD health research priorities with a sample of patients from two community health centers. Thematic analyses were conducted and restricted to social factors impacting health. Findings were incorporated into the development of The LEGACY Project, a longitudinal cohort of TGD patients, assessing the impact of gender-affirming care on health outcomes. RESULTS: Cross-cutting themes about TGD research priorities pertaining to social factors and health included: (1) Embodiment: understanding and investigating the complex and intersectional lived experiences of TGD individuals; (2) Social determinants of health: the impact of structural and interpersonal stigma on TGD health; and (3) Resiliency and health promoting factors: the need to expand public health research beyond disparities to assess resiliency and health promotion in TGD communities. CONCLUSIONS: Participants identified investigating the impact of social influences on health as a research priority for TGD patients. Recalibrating field norms from individual researcher priorities to TGD population-driven research will help ensure investigators address topics that may otherwise be missed or overlooked and may optimize the reach and impact of research in TGD health.

Patient-centered practices for engaging transgender and gender diverse patients in clinical research studies.

BACKGROUND: The purpose of this formative study was to assess barriers and facilitators to participation of transgender and gender diverse (TGD) patients in clinical research to solicit specific feedback on perceived acceptability and feasibility of research methods to inform creation of a multisite longitudinal cohort of primary care patients engaged in care at two community health centers. METHOD: Between September-November 2018, four focus groups (FGs) were convened at two community health centers in Boston, MA and New York, NY (N = 28 participants across all 4 groups; 11 in Boston and 17 in New York). FG guides asked about patient outreach, acceptability of study methods and measures, and ideas for study retention. FGs were facilitated by TGD study staff, lasted approximately 90 min in duration, were audio recorded, and then transcribed verbatim by a professional transcription service. Thematic analyses were conducted by two independent analysts applying a constant comparison method. Consistency and consensus were achieved across code creation and application aided by Dedoose software. RESULTS: Participants were a mean age of 33.9 years (SD 12.3; Range 18-66). Participants varied in gender identity with 4 (14.3%) men, 3 (10.7%) women, 8 (28.6%) transgender men, 10 (35.7%) transgender women, and 3 (10.7%) nonbinary. Eight (26.6%) were Latinx, 5 (17.9%) Black, 3 (10.7%) Asian, 3 (10.7%) another race, and 5 (17.9%) multiracial. Motivators and facilitators to participation were: research creating community, research led by TGD staff, compensation, research integrated into healthcare, research applicable to TGD and non-TGD people, and research helping TGD communities. Barriers were: being research/healthcare averse, not identifying as TGD, overlooking questioning individuals, research coming from a 'cisgender lens", distrust of how the research will be used, research not being accessible to TGD people, and research being exploitative. CONCLUSION: Though similarities emerged between the perspectives of TGD people and research citing perspectives of other underserved populations, there are barriers and facilitators to research which are unique to TGD populations. It is important for TGD people to be involved as collaborators in all aspects of research that concerns them.

FBXO22, an epigenetic multiplayer coordinating senescence, hormone signaling, and metastasis.

Ubiquitin-dependent protein degradation has been implicated in the control of various cellular processes such as cell cycle control, transcriptional regulation, DNA damage repair, and apoptosis, many of which are involved in the initiation, progression, metastasis, and drug resistance of cancers. E3 ubiquitin ligases are known to be the second most prevalent cancer-related functional gene family next to protein kinases. Of these, FBXO22, an F-box receptor subunit of SCF E3 ligase, has recently been proposed to play a critical role in multiple aspects related to cancer development and therapy response. Firstly, FBXO22 is a key regulator of senescence induction through ubiquitylation of p53 for degradation. FBXO22 also acts as a molecular switch for the antagonistic and agonistic actions of selective estrogen receptor modulators (SERM) and determines the sensitivity of breast cancer to SERM by ubiquitylating KDM4B complexed with unliganded or SERMs-bound estrogen receptor (ER). Furthermore, FBXO22 binds to Bach1, a pro-metastatic transcription factor, suppressing Bach1-driven metastasis of lung adenocarcinoma, and loss of FBXO22 facilitates metastasis. These findings, as well as other reports, unveiled strikingly important roles of FBXO22 in cancer development and therapeutic strategy. In this review, we summarize recent findings of how FBXO22 regulates major cancer suppression pathways.

Click Nucleic Acid Mediated Loading of Prodrug Activating Enzymes in PEG-PLGA Nanoparticles for Combination Chemotherapy.

The simultaneous delivery of multiple therapeutics to a single site has shown promise for cancer targeting and treatment. However, because of the inherent differences in charge and size between drugs and biomolecules, new approaches are required for colocalization of unlike components in one delivery vehicle. In this work, we demonstrate that triblock copolymers containing click nucleic acids (CNAs) can be used to simultaneously load a prodrug enzyme (cytosine deaminase, CodA) and a chemotherapy drug (doxorubicin, DOX) in a single polymer nanoparticle. CNAs are synthetic analogs of DNA comprised of a thiolene backbone and nucleotide bases that can hybridize to complementary strands of DNA. In this study, CodA was appended with complementary DNA sequences and fluorescent dyes to allow its encapsulation in PEG-CNA-PLGA nanoparticles. The DNA-modified CodA was found to retain its enzyme activity for converting prodrug 5-fluorocytosine (5-FC) to active 5-fluorouracil (5-FU) using a modified fluorescent assay. The DNA-conjugated CodA was then loaded into the PEG-CNA-PLGA nanoparticles and tested for cell cytotoxicity in the presence of the 5-FC prodrug. To study the effect of coloading DOX and CodA within a single nanoparticle, cell toxicity assays were run to compare dually loaded nanoparticles with nanoparticles loaded only with either DOX or CodA. We show that the highest level of cell death occurred when both DOX and CodA were simultaneously entrapped and delivered to cells in the presence of 5-FC.

Predicting neural recording performance of implantable electrodes.

Recordings of neural activity can be used to aid communication, control prosthetic devices or alleviate disease symptoms. Chronic recordings require a high signal-to-noise ratio that is stable for years. Current cortical devices generally fail within months to years after implantation. Development of novel devices to increase lifetime requires valid testing protocols and a knowledge of the critical parameters controlling electrophysiological performance. Here we present electrochemical and electrophysiological protocols for assessing implantable electrodes. Biological noise from neural recording has significant impact on signal-to-noise ratio. A recently developed surgical approach was utilised to reduce biological noise. This allowed correlation of electrochemical and electrophysiological behaviour. The impedance versus frequency of modified electrodes was non-linear. It was found that impedance at low frequencies was a stronger predictor of electrophysiological performance than the typically reported impedance at 1 kHz. Low frequency impedance is a function of electrode area, and a strong correlation of electrode area with electrophysiological response was also seen. Use of these standardised testing protocols will allow future devices to be compared before transfer to preclinical and clinical trials.