Evaluation of Intradermal and Subcutaneous Infusion Set Performance Under 24-Hour Basal and Bolus Conditions

New ex vivo method to objectively assess insulin spatial subcutaneous dispersion through time during pump basal-rate based administration

Glycemic variability remains frequent in patients with type 1 diabetes treated with insulin pumps. Heterogeneous spreads of insulin infused by pump in the subcutaneous (SC) tissue are suspected but were barely studied. We propose a new real-time ex-vivo method built by combining high-precision imaging with simultaneous pressure measurements, to obtain a real-time follow-up of insulin subcutaneous propagation. Human skin explants from post-bariatric surgery are imaged in a micro-computed tomography scanner, with optimised parameters to reach one 3D image every 5 min during 3 h of 1UI/h infusion. Pressure inside the tubing is recorded. A new index of dispersion (IoD) is introduced and computed upon the segmented 3D insulin depot per time-step. Infusions were hypodermal in 58.3% among 24 assays, others being intradermal or extradermal. Several minor bubbles and one occlusion were observed. IoD increases with time for all injections. Inter-assay variability is the smallest for hypodermal infusions. Pressure elevations were observed, synchronised with air bubbles arrivals in the tissue. Results encourage the use of this method to compare infusion parameters such as pump model, basal rate, catheter characteristics, infusion site characteristics or patient phenotype.

A Comparison of Flow- and Pressure-Controlled Infusion Strategies for Microneedle-based Transdermal Drug Delivery

Microneedle-based transdermal drug delivery is considered an attractive alternative to conventional injections using hypodermic needles due to its minimally invasive and painless nature; this has the potential to improve patient adherence to medication regimens. Hollow microneedles (MNs) are sharp, sub-millimeter protrusions with a channel that serves as a fluidic interface with the skin. This technology could be coupled with micro-pumps, embedded sensors, actuators and electronics to create Micro Transdermal Interface Platforms - smart, wearable infusion systems capable of delivering precise microdoses over a prolonged period. Using 500 µm tall hollow microneedles, ex-vivo human skin and a customized application/retraction device, this work focuses on comparing two infusion control strategies, namely 'set pressure' (SP) and 'set flow' (SF) infusion. It was found that flow-controlled infusion was capable of delivering higher volumes than pressure-driven delivery, and a mean volume of 3.8 mL was delivered using a set flowrate of 50 µL/minute. This suggests that flow driven delivery is a better control strategy and confirms that MN array retraction is beneficial for transdermal MN infusion.

Advances of microneedles in hormone delivery

The skin is recognized as a potential target for local and systemic drug delivery and hormone. However, the transdermal route of drug administration seems to be limited by substantial barrier properties of the skin. Recently, delivering hormone via the skin by transdermal patches is a big challenge because of the presence of the stratum corneum that prevents the application of hormone via this route. In order to overcome the limitations, microneedle (MN), consisting of micro-sized needles, are a promising approach to drill the stratum corneum and release hormone into the dermis via a minimal-invasive route. This review aimed to highlight advances in research on the development of MNs-based therapeutics for their implications in hormone delivery. The challenges during clinical translation of MNs from bench to bedside are also discussed.

Inducible Pluripotent Stem Cells as a Potential Cure for Diabetes

Over the last century, diabetes has been treated with subcutaneous insulin, a discovery that enabled patients to forego death from hyperglycemia. Despite novel insulin formulations, patients with diabetes continue to suffer morbidity and mortality with unsustainable costs to the health care system. Continuous glucose monitoring, wearable insulin pumps, and closed-loop artificial pancreas systems represent an advance, but still fail to recreate physiologic euglycemia and are not universally available. Islet cell transplantation has evolved into a successful modality for treating a subset of patients with ‘brittle’ diabetes but is limited by organ donor supply and immunosuppression requirements. A novel approach involves generating autologous or immune-protected islet cells for transplant from inducible pluripotent stem cells to eliminate detrimental immune responses and organ supply limitations. In this review, we briefly discuss novel mechanisms for subcutaneous insulin delivery and define their shortfalls. We describe embryological development and physiology of islets to better understand their role in glycemic control and, finally, discuss cell-based therapies for diabetes and barriers to widespread use. In response to these barriers, we present the promise of stem cell therapy, and review the current gaps requiring solutions to enable widespread use of stem cells as a potential cure for diabetes.

Evaluating the Impact of Human Factors and Pen Needle Design on Insulin Pen Injection

BACKGROUND

Limited published data exists quantifying the influence of human factors (HF) and pen needle (PN) design on delivery outcomes of pen injection systems. This preclinical in vivo study examines the impact of PN hub design and applied force against the skin during injection on needle penetration depth (NPD).

METHOD

To precisely locate injection depth, PN injections (20 µl; 2 IU, U-100 volume equivalent) of iodinated contrast agent were administered to the flank of Yorkshire swine across a range of clinically relevant application forces against the skin (0.25, 0.75, 1.25, and 2.0 lbf). The NPD, representing in vivo needle tip depth in SC tissue, from four 32 G × 4 mm PN devices (BD Nano^™ 2nd Gen and three commercial posted-hub PN devices; n = 75/device/force, 1200 total) was measured by fluoroscopic imaging of the resulting depot.

RESULTS

The reengineered hub design more closely achieved the 4 mm target NPD with significantly less variability ( P = .006) than commercial posted-hub PN devices across the range of applied injection forces. Calculations of IM (intramuscular) injection risk completed through in silico probability model, using NPD and average human tissue thickness measurements, displayed a commensurate reduction (~2-8x) compared to conventional PN hub designs.

CONCLUSIONS

Quantifiable differences in injection depth were observed between identical labeled length PN devices indicating that hub design features, coupled with aspects of variable injection technique, may influence injection depth accuracy and consistency. The reengineered hub design may reduce the impact of unintended individual technique differences by improving target injection depth consistency and reducing IM injection potential.

Home Use of Day-and-Night Hybrid Closed-Loop Insulin Delivery in Very Young Children: A Multicenter, 3-Week, Randomized Trial

OBJECTIVE

We aimed to assess the feasibility and safety of hybrid closed-loop insulin delivery in children with type 1 diabetes aged 1-7 years as well as evaluate the role of diluted insulin on glucose control.

RESEARCH DESIGN AND METHODS

In an open-label, multicenter, multinational, randomized crossover study, 24 children with type 1 diabetes on insulin pump therapy (median age 5 years [interquartile range 3-6] and mean ± SD HbA_1c 7.4 ± 0.7% [57 ± 8 mmol/mol] and total insulin 13.2 ± 4.8 units/day) underwent two 21-day periods of unrestricted living and we compared hybrid closed-loop with diluted insulin (U20) and hybrid closed-loop with standard strength insulin (U100) in random order. During both interventions, the Cambridge model predictive control algorithm was used.

RESULTS

The proportion of time that sensor glucose was in the target range between 3.9 and 10 mmol/L (primary end point) was not different between interventions (mean ± SD 72 ± 8% vs. 70 ± 7% for closed-loop with diluted insulin vs. closed-loop with standard insulin, respectively; P = 0.16). There was no difference in mean glucose levels (8.0 ± 0.8 vs. 8.2 ± 0.6 mmol/L; P = 0.14), glucose variability (SD of sensor glucose 3.1 ± 0.5 vs. 3.2 ± 0.4 mmol/L; P = 0.16), or the proportion of time spent with sensor glucose <3.9 mmol/L (4.5 ± 1.7% vs. 4.7 ± 1.4%; P = 0.47) or <2.8 mmol/L (0.6 ± 0.5% vs. 0.6 ± 0.4%; P > 0.99). Total daily insulin delivery did not differ (17.3 ± 5.6 vs. 18.9 ± 6.9 units/day; P = 0.07). No closed-loop-related severe hypoglycemia or ketoacidosis occurred.

CONCLUSIONS

Unrestricted home use of day-and-night closed-loop in very young children with type 1 diabetes is feasible and safe. The use of diluted insulin during closed-loop does not provide additional benefits compared with standard strength insulin.

Navigating Two Roads to Glucose Normalization in Diabetes: Automated Insulin Delivery Devices and Cell Therapy

Incredible strides have been made since the discovery of insulin almost 100 years ago. Insulin formulations have improved dramatically, glucose levels can be measured continuously, and recently first-generation biomechanical "artificial pancreas" systems have been approved by regulators around the globe. However, still only a small fraction of patients with diabetes achieve glycemic goals. Replacement of insulin-producing cells via transplantation shows significant promise, but is limited in application due to supply constraints (cadaver-based) and the need for chronic immunosuppression. Over the past decade, significant progress has been made to address these barriers to widespread implementation of a cell therapy. Can glucose levels in people with diabetes be normalized with artificial pancreas systems or via cell replacement approaches? Here we review the road ahead, including the challenges and opportunities of both approaches.

New Insulin Delivery Recommendations

Many primary care professionals manage injection or infusion therapies in patients with diabetes. Few published guidelines have been available to help such professionals and their patients manage these therapies. Herein, we present new, practical, and comprehensive recommendations for diabetes injections and infusions. These recommendations were informed by a large international survey of current practice and were written and vetted by 183 diabetes experts from 54 countries at the Forum for Injection Technique and Therapy: Expert Recommendations (FITTER) workshop held in Rome, Italy, in 2015. Recommendations are organized around the themes of anatomy, physiology, pathology, psychology, and technology. Key among the recommendations are that the shortest needles (currently the 4-mm pen and 6-mm syringe needles) are safe, effective, and less painful and should be the first-line choice in all patient categories; intramuscular injections should be avoided, especially with long-acting insulins, because severe hypoglycemia may result; lipohypertrophy is a frequent complication of therapy that distorts insulin absorption, and, therefore, injections and infusions should not be given into these lesions and correct site rotation will help prevent them; effective long-term therapy with insulin is critically dependent on addressing psychological hurdles upstream, even before insulin has been started; inappropriate disposal of used sharps poses a risk of infection with blood-borne pathogens; and mitigation is possible with proper training, effective disposal strategies, and the use of safety devices. Adherence to these new recommendations should lead to more effective therapies, improved outcomes, and lower costs for patients with diabetes.

Insulin Infusion Sets: A Critical Reappraisal

An insulin infusion set (IIS) is a key component of insulin pumps. In daily practice issues with the IIS appear to be as relevant for a successful insulin therapy as the pumps themselves. The insulin is applied to the subcutaneous tissue via a Teflon(®) (Dupont, Wilmington, DE) or steel cannula. There are intensive discussions about the impact the choice of material for insulin application has on insulin pharmacokinetics. In this review, this factor and others that are known to have an impact on the successful usage of IIS are discussed.