FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * LUDVIGSON DAVID   2. Issuer Name and Ticker or Trading Symbol NANOGEN INC [NGEN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) President & COO (Last) (First) (Middle) 10398 PACIFIC CENTER CT. 3. Date of Earliest Transaction (Month/Day/Year) 07/29/2005 (Street) SAN DIEGO, CA 92121 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 12/31/2004   P   1,666 (1) A $ 2.499 48,192 D   Common Stock 06/30/2005   P   1,666 (1) A $ 2.499 49,858 D   Common Stock 07/29/2005   A   50,000 (2) A $ 0.001 99,858 D

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Incentive Stock Option

$ 3.45

06/01/2003

07/18/2013

Common Stock

86,955

86,955

D

Non-Qualified Stock Option

$ 2.8

06/14/2003

07/18/2008

Common Stock

10,000

10,000

D

Non-Qualified Stock Option

$ 6.96

04/26/2002

07/18/2008

Common Stock

36,666

36,666

D

Non-Qualified Stock Option

$ 8.6

06/13/2002

07/18/2008

Common Stock

10,000

10,000

D

Incentive Stock Option

$ 6.62

06/01/2004

06/01/2014

Common Stock

45,315

45,315

D

Non-Qualified Stock Option

$ 6.62

06/01/2004

06/01/2014

Common Stock

254,685

254,685

D

Non-Qualified Stock Option

$ 3.45

06/01/2003

07/18/2013

Common Stock

154,837

154,837

D

Non-Qualified Stock Option

$ 4.7

01/29/2005

07/29/2014

Common Stock

150,000

150,000

D

Non-Qualified Stock Option

$ 4.4

07/29/2005

A

75,000

01/29/2006(3)

07/29/2015

Common Stock

75,000

$ 4.4

75,000

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
LUDVIGSON DAVID 10398 PACIFIC CENTER CT. SAN DIEGO, CA 92121			President & COO

Signatures

/S/ David Ludvigson		08/02/2005
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Shares purchased through ESPP.
(2)	Shares subject to a Restricted Stock Unit award which vest and become issuable on July 29, 2007
(3)	Option vests ratably on a monthly basis over a 2 year period beginning 6 months from date of grant with continued service.

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