implantable biosensor with programmed insulin pump

1. Implantable Biosensor
Programmed Insulin Pump

2. What is Implanted Insulin
Pump
An implanted insulin pump is a pump which remains inside the body at
all times. An implanted insulin pump is able to deliver insulin into the
peritoneal cavity which has a rich supply of blood vessels and can
therefore absorb insulin very efficiently

3. Types of pumps
Open loop pumps
• The insulin pump is controlled by the
user to bolus manually based on a
recent blood glucose measurement
and an estimate of the grams of
carbohydrate consumed. This
predictive approach is said to be
open-loop .Once a bolus has been
calculated and delivered, the pump
continues to deliver its basal rate
insulin in the manner that has been
programmed into the pump which
controls based on the predicted
insulin requirements of its user.
Closed loop pumps
• A closed-loop insulin delivery system
is essentially an artificial pancreas.
The loop refers to the continuous
cycle of feedback information, the
blood glucose level changes. this
change is detected by the continuous
glucose monitor (CGM). then CGM
sends information to the insulin
pump, which adjusts its insulin output
and the blood glucose level changes
again in response to the insulin. The
loop is closed when this happens
automatically

4. What is APDS?
An artificial pancreas device system (also known
as an APD system, AP or APDS) is a small,
portable medical device that is being designed
to carry out the function of a healthy pancreas
in controlling blood glucose levels. It uses digital
communication technology to automate insulin
delivery. An APD system is worn externally on
the body, and is made up of three functional
components:
A. A continuous glucose monitor (CGM),A
digital controller, An insulin pump .
B. the CGM and insulin pump are linked
together for the first time by a digital
controller device (the ‘brain’ or ‘control
centre’) containing a control algorithm. An
algorithm is a set of rules by which
information can be quickly processed
through a series of steps to arrive at a
logical decision about what needs to be
done next. Algorithms are usually written
out as a set of mathematical equations, and
are used quite widely in medicine to help
healthcare professionals reach logical and
consistent decisions about patient care
when the information going into that
decision is complex.

5. Components and its
working
(1) Continuous Glucose Monitor (CGM).-A CGM
provides a steady stream of information that is
intended to reflect the patient’s blood glucose levels. A
sensor placed under the patient's skin (subcutaneously)
measures the glucose in the fluid around the cells
(interstitial fluid), which has been found to correlate
with blood glucose levels. A small transmitter sends
information to a receiver. A CGM continuously displays
both an estimate of blood glucose levels and their
direction and rate of change of these estimates.
(2)Blood Glucose Device (BGD)- Currently, to get the
most accurate estimates of blood glucose possible from
a CGM, the patient needs to periodically calibrate the
CGM using a blood glucose measurement from a BGD,
therefore, the BGD still plays a critical role in the proper
management of patients with an APDS. However, over
time, we anticipate that improved CGM performance
may obviate the need for periodic blood glucose checks
with a BGD.
(3) APDS Control algorithm-An APDS control algorithm
is software embedded in an external processor
(controller) that receives information from the CGM
and performs a series of mathematical calculations.
Based on these calculations, the controller sends
dosing instructions to the infusion pump.
(4) Infusion pump- Based on the instructions sent by
the controller, an infusion pump adjusts the insulin
delivery to the subcutaneous tissue.
(5) The Patient-The patient is an important part of the
APDS. The concentration of glucose circulating in the
patient’s blood is constantly changing. It is affected by
the patient’s diet, activity level, and how his or her
body metabolizes insulin and other substances.

6. VAPOUR PRESSURE
PUMP MECHANISM
The driving force generated by gas vapour
(usually Freon).Consists of two chambers :
stored insulin and vapor system.Vapour in a
compartment will push against bellow
chamber that contains insulin. Pressure
against bellow is constant regardless of
amount of insulin. Infusion rate is
determined by an outflow restrictor. Based
on diagram in previous slide, there is two
outflow restrictor.When valve activated, one
of the flow restrictor will be bypassed. If
valve not activated, insulin will still flow out
but infusion rate is restricted. Thus, insulin
will be continuously delivered. The amount
of insulin (i.e. infusion rate) depends on
outflow restrictor. No parts giving rise to
friction. No need of electrical energy for
pumping. But care must be taken in the
vapor pressure. Pressure might rise due to
ambient pressure and other factors. This
might lead to uncontrollable infusion.

7. Fabrication of thin film
insulin pump
I. Sputtered films of nickel-titanium are first
deposited on a silicon wafer.
II. After sputtering, the backside of the silicon
substrate is etched away exposing a small area of
the alloy film. This area is then hot deformed at
480C by a spherically pointed probe.
III. In typical actuators a shape memory alloy spring
is opposed by a conventional spring. When
heated the shape memory spring expands,
overcoming the bias spring and exerting some
output force.
IV. For the case of the thin film diaphragm, which is
to change from a flat to a dome shape to create a
pumping action, some form of biasing force is
also required.
V. By manipulating the sputtering process a thin
film can be deposited with a composition
gradient varying from equiatomic nickel-titanium
to a nickel rich composition. The equiatomic film
exhibits shape memory and the high nickel part
of the film acts as a restraining force or bias.
VI. When this composite film is deformed at a high
temperature, this shape is imprinted in the film.
When the film cools the bias layer forces the film
into the flat position, but when the film is heated
it returns to the dome shape imprinted by the
hot deformation process. The sequence of the
processes to produce a single thin film diaphragm
pump is given in fig .

8. Importance of Check
valves
Check valves for microfluidic devices are of
two types are ball check and disc. The ball
check valves have excellent sealing against
reverse flow and unrestricted flow in the
positive direction; however, they are fairly
large in terms of the pump body volume
envisioned, although miniaturization is
possible.
The disc type valve is smaller, has good back
flow characteristics and excellent forward
flow and does not easily foul.they also can
fabricate in an even smaller version on
special order. If the available check valves do
not suite the envelope required, flapper
valves photoetched from a silicon substrate
can be explored; these been used in fluidic
control systems.

9. The control system
The control system will consist of the following: a precision 0.01% temperature compensated
voltage reference for sensor excitation, analog input operational amplifiers to raise the sensor
voltage signal to a more useful value, MOSFET switches for switching DC power to the thin film
diaphragms and for switching analog signals, and a sophisticated micro-controller with analog to
digital conversion, serial communications, high current output channels and all needed support
circuitry, including “sleep timer” and EEPROM. The insulin pump will be controlled by a standard
PID control algorithm. The Proportional-Integral-Differential control is broadly used where
system response can lag behind the control output by a significant amount of time, ranging from
milliseconds to tens of minutes. Tuning the PID algorithm can be carried out to accommodate
the variation in drug delivery rate required. For the insulin pump the rate must be controllable
to match the wide types of insulin which might be used, with the objective of minimizing
divergence of glucose levels from the desired 5.6 mmol/l.

10. The Glucose sensor
Glucose monitoring system measure hydrogen peroxide.
Hydrogen peroxide produced by the enzymatic reaction of glucose at the site
of the immobilized glucose oxidase membrane.
Glucose + O2 → Gluconiuc acid + H2O2
For needle type glucose sensor, sensor consisting of a platinum anode and a
silver cathode.
The electrodes, loaded with 0.6 V polarographic voltage, measure hydrogen
peroxide.
Needle-type glucose sensors were inserted into the subcutaneous tissue of the
forearm or the abdomen

11. Block Diagram of
Insulin Pump
The system consists of a glucose sensor strip
to measure the glucose level and the
electrical signal obtained was amplified and
fed to the micro controller. The micro-
controller reads the current glucose level and
calculates the amount of insulin required
based on the treatment parameters set by
the physician and this quantity of insulin is
then pumped into the patient’s blood. The
microcontroller is programmed in such a way
that the blood glucose level is monitored at a
time interval of 2 hours and the data is read
by the micro controller (also, the pump
permits possibility for measuring blood
glucose level at other intervals according to
patient’s requirement). Revised and
appropriate quantity of insulin is again
pumped and this process repeats to maintain
the desired level of glucose in the patient’s
blood.

12. Fabrication of Glucose Sensor

13. Advantages and Disadvantages of insulin
pump
Pros
• Less jabs
• Take insulin as and when you need it
• Have different basal rates at different times
of the day
• Flexibilty with food
• Flexibitity with exercise
• Increase blood glucose control
• Reducing episodes of severe hypoglycaemia
Cons
• Difficult getting a pump on NHS
• Cost: if buying by yourself
• Steep learning curve
• Frequent blood testing required
• Changing infusion set more difficult than
changing injection
• Risk of diabetic ketoacidosis
• Skin infection
• Tubing of insulin pumps getting caught on
objects

14. Application in treatment of type
2 diabetes patient
5 patients with Type II diabetes by means of a subcutaneously implanted
intravenous insulin pump and compared their metabolic response with that
observed during conventional insulin therapy. The use of the pump improved
control of glycaemia, as manifested by reductions in mean plasma glucose
(from 188±46 to 106±12 mg per decilitre ), fasting glucose (from 187±42 to
80±13 mg per decilitre), and postprandial glucose (from 287±74 to 182±29 mg
per decilitre), together with a diminution of glycaemic excursion and
normalization of glycosylated haemoglobin A1 (from 12.1 ±2 to 8.0±1 per cent).
At the end of the study the pumps had been in place for a mean of 7.0 months
(range, 5.5 to 9.7 months) without mishap and with good patient acceptance.
Improved blood glucose control can be achieved by means of a permanently
implanted continuous insulin-infusion device in ambulatory patients with Type
II diabetes who require insulin, and that the need for daily insulin injections
can thereby be eliminated.

15. Thank you